Environmental sensing and response genes in Cnidaria: the chemical defensome in the sea anemone Nematostella vectensis (2024)

The publisher's final edited version of this article is available at Cell Biol Toxicol

The starlet sea anemone Nematostella vectensis has been recently established as a new model system for the study of the evolution of developmental processes, as cnidaria occupy a key evolutionary position at the base of the bilateria. Cnidaria play important roles in estuarine and reef communities, but are exposed to many environmental stressors.

Here I describe the genetic components of a ‘chemical defensome’ in the genome of N. vectensis, and review cnidarian molecular toxicology. Gene families that defend against chemical stressors and the transcription factors that regulate these genes have been termed a ‘chemical defensome,’ and include the cytochromes P450 and other oxidases, various conjugating enyzymes, the ATP-dependent efflux transporters, oxidative detoxification proteins, as well as various transcription factors. These genes account for about 1% (266/27200) of the predicted genes in the sea anemone genome, similar to the proportion observed in tunicates and humans, but lower than that observed in sea urchins. While there are comparable numbers of stress-response genes, the stress sensor genes appear to be reduced in N. vectensis relative to many model protostomes and deuterostomes. Cnidarian toxicology is understudied, especially given the important ecological roles of many cnidarian species. New genomic resources should stimulate the study of chemical stress sensing and response mechanisms in cnidaria, and allow us to further illuminate the evolution of chemical defense gene networks.

Table 1

Receptors and Signal Transduction

hom*ologs of most important stress receptors are present in the sea anemone genome, including the aryl hydrocarbon receptor (AHR), hypoxia-inducible factor 1 (HIF1α), and the aryl hydrocarbon nuclear translocator (ARNT), metal transcription factor 1 (MTF1), nuclear factor-kappa B (NFkB), and nuclear factor erythroid-derived 2 related 2 (NRF2), detailed below (Figure 2). Although some of the known components of the vertebrate and invertebrate xenobiotic receptor pathways are missing (e.g. pregnane X receptor, liver X receptor, farnesoid X receptor [PXR, LXR, and FXR]), receptors that are not clearly orthologous to known xenobiotic sensors may substitute, or there may be increased xenobiotic receptor promiscuity.

Open in a separate window

Figure 2

Some of the stress response transcription factor pathways with hom*ologs in N. vectensis. Hypoxia activates both the HIF1α and MTF1 pathway, metal stress activates MTF1, oxidative stress activates the NRF2 pathway (as well as others, not shown), and organic xenobiotics activate AHR or various NRs. These transcription factors have specific response elements (REs) in the regulatory regions of responsive genes, including hypoxida RE (HRE; HIF1α/ARNT), metal RE (MRE; MTF1), antioxidant RE (ARE; NRF2), xenobiotic RE (XRE; AHR/ARNT), and specific NR-REs (e.g. estrogen response elements).

Efflux Transporter Proteins

Many toxic compounds are pumped against concentration gradients across membranes in an energy-dependent process. This first line of cellular defense, against amphipathic or slightly lipophilic compounds in particular, is mediated by efflux proteins known as ATP Binding Cassette (ABC) or multidrug efflux transporters, including the p-glycoproteins (PGP/ABCB), mitoxantrone resistance protein (MXR/ABCG2), and multidrug resistance proteins (MRP/ABCC) (Dean et al, 2001). Efflux transporters function to export both unmodified substrates and substrates modified by other defensome enzymes (Deeley et al, 2006). In embryos, efflux transporters may provide the primary defense against exogenous toxicants but also play important roles in developmental programs by establishing morphogen gradients (Hamdoun and Epel, 2007).

In chordates the ABC transporters are organized into 8 subfamilies designated ABC A through H (Annilo et al, 2006). A subset of these families includes proteins known to export toxicants: the ABCB, ABCC and ABCG transporters. These proteins are commonly called multidrug resistance (MDR) transporters after their ability to pump out multiple therapeutic drugs, a major obstacle to the efficacy of the treatment of several pathogens (Dean et al, 2005).

Genome searches revealed that sea anemones have 64 ABC genes organized into 6 subfamilies including the three multidrug transporter subfamilies (ABC B, C and G; Table 1, Supplemental Table S1). There is considerable variation in the total number of ABC genes within eukaryotic genomes, but the relative proportions have tended to stay constant (Annilo et al, 2006; Goldstone et al, 2006). The ABC genes clustered in the ABCA (5 genes), ABCD (6 genes), and ABCF (4 genes) families either do not have known function, or do not have known roles in detoxification, and will not be considered further here.

N. vectensis has 7 ABCB genes, including two related to the ABCB1 (pgp) proteins. The pgp transporters are well known as multidrug resistance proteins involved in the efflux of toxic compounds. Additional genes related to known xenobiotic transporters include 6 ABCC4 (MRP4)-like genes, found in a sea anemone-specific cluster, 6 other ABCC-like genes including one ABCC5 (MRP5)-like sequence, and 24 other genes that cluster in a large anemone-specific clade within the ABCC family. Finally, analyses conducted in this study identified 6 ABCG sequences, including one sequence that clusters closely with the vertebrate ABCG2s. In vertebrates, ABCG2 proteins exhibit broad substrate specificity among xenobiotic compounds, and play critical roles in the clearance of certain drugs (Allikmets et al, 1998; Kusuhara and Sugiyama, 2007; Miyake et al, 1999).

Other potentially important anemone transporters include the organic anion polypeptides (OATP; solute carrier family 21, SLC21) and organic anion and cation transporters (OAT and OCT; solute carrier family 22, SLC22). Both SLC21 and SLC22 are part of the major facilitator superfamily. OAT substrates examined in vertebrates include estrone sulfate, urate, prostaglandins, heavy metals such as mercury and cadmium, and the herbicide 2,4-dichlorophenoxyacetic acid (Eraly et al, 2004; Kimura et al, 2002; Sweet, 2005). OATPs have partially overlapping substrate specificities for steroid conjugates, bile salts, anionic oligopeptides, and anionic xenobiotics including toxins and drugs (Hagenbuch and Meier, 2003; Jacobsson et al, 2007). The anemone genome contains 17 OATP genes, and 62 SLC22 (OCT and OAT) genes. However, orthology among non-vertebrate SLC families is difficult to assign, precluding any hypotheses regarding substrate specificity.

Oxidative or Reductive Biotransformation

Cytochromes P450

Oxidative modification of chemicals to more hydrophilic products is often the initial step leading to excretion. In bilaterians this is carried out by cytochrome P450 (CYP) and flavoprotein monooxygenase (FMO) enzymes, especially members of the CYP1, CYP2, CYP3, CYP6, CYP9, and CYP4 families. Toxicant oxidation can, however, also lead to increased toxicity; for example, oxidation of benzo[a]pyrene by CYP1A leads to hepatotoxicity (Uno et al, 2001).

The sea anemone genome contains 82 CYP genes, which are in general not classifiable into established CYP families due to the low (<40%) identity with other known CYPs. A large scale reclassification of metazoan CYPs taking into account recent genomic data will be required to formally name the N. vectensis CYPs (Nelson, personal communication). However, broader classification into the CYP clan framework (Nelson, 1998, 2006) is possible: Clan 2, containing CYP families 1,2,17, 18, 21, 33, 34, and 35; Clan 3, containing primarily CYPs 3, 5, 6, 9, 28, 309, 310, and 317; Clan 4, containing CYPs 4, 311, 313, 316, and 318; and the mitochondrial clan, CYPs 11, 12, 24, 27, 44, 49, 302, 314, and 315.

Sea anemone CYPs are principally part of Clan 2 and Clan 3, with 39 and 20 genes in these two Clans, respectively, while there are only 3 Clan 4 genes (Table 2, Figure 3, Supplemental Figure S1, Supplemental Table S2). Many of the CYPs in these clans are involved in detoxification of exogenous and endogenous compounds (Lewis et al, 2004), although the functional information is primarily from vertebrates and insects. The anemone Clan2 CYPs are clustered more closely to the vertebrate CYP17s (and thus the important xenobiotic-detoxifying CYP1s, including aryl hydrocarbon hydroxylases) than to the vertebrate CYP2s. However, it is not clear that CYP1 genes exist outside the deuterostomes (Goldstone et al, 2007), and these sea anemone CYPs cannot be considered early CYP1-like genes. The Clan 3 genes are likewise less closely related to the vertebrate CYP3 or insect CYP6 detoxification genes than to other members of Clan 3, in this case the CYP5-like genes. CYP5 genes have unusual functionality in that they catalyze a rearrangement of a prostaglandin endoperoxide (Hecker and Ullrich, 1989), rather than a substrate oxidation. More generally, the sea anemone Clan 3 CYPs may oxidize prostaglandins, which are potent chemical defenses in marine systems (Paul and Puglisi, 2004; Paul et al, 2006).

Open in a separate window

Figure 3

Distribution of genes in CYP Clans in human, tunicate, sea urchin, and sea anemone. Data for the tunicate and sea urchin assignments was taken from (Goldstone et al, 2006).

Table 2

Gene counts of biotransformative genes in the humans, sea urchin, and sea anemone genomes.

Classification	Gene	Human	Urchin	Anemone
Oxidative	CYP Clan 2	21	85	39
	CYP Clan 3	5	13	20
	CYP Clan 4	12	10	3
	FMO	6	16	6
	ALDH	19	20	21
Conjugative	GST	21	38	18
	MGST	3	12	5
	SULT	13	73	22
	UGT	13a	50	9
	NAT	2	1	0
Reductive	AKR-like	8	10	12
	EPHX	2	5	1
	NOQ1	2	0	0

Open in a separate window

^aNot applicable – see text.

^bNot including multiple first exon expression in UGT1.

N. vectensis does not have a CYP19 (aromatase), despite the fact that (low) aromatase activity has been demonstrated in a scleractinian coral, Euphillia ancora (Twan et al, 2003). CYP19 is not present in most invertebrates with a sequenced genome (Goldstone, Nelson, and Stegeman, unpublished data), although it is present in amphioxus (Castro et al, 2005; Mizuta and Kubokawa, 2007). It is very possible that a different CYP, not CYP19, possesses aromatase activity.

Conjugative Biotransformation

Sea anemones possess relatively few proteins with direct hom*ology to xenobiotic-conjugating enzymes, particularly in comparison to the purple sea urchin (Table 2; (Goldstone et al, 2006). Sea anemones have genes for 23 glutathione-S-transferases (GST) including 5 microsomal GSTs (MAPEG), 9 UDP-glucuronosyl transferase (UGT) genes, and 22 sulfotransferase (SULT) genes. No N-acetyl transferase (NAT) genes were found. These numbers are far lower than the large diversification of these gene families seen in sea urchins, but comparable to the numbers observed in mammalian genomes (the human genome contains 13 SULT, 13 UGT, and 21 GST genes; (Gamage et al, 2006; Mackenzie et al, 2005; Nebert and Vasiliou, 2004)).

Cytosolic GSTs are soluble proteins that catalyze the transfer of glutathione to an electrophilic substrate (Hayes et al, 2005). Microsomal, or membrane, GSTs (MAPEG) form an evolutionarily distinct class of enzymes that exhibit both glutathione transferase and lipid peroxidase activity (Bresell et al, 2005), thus detoxifying both xenobiotic compounds and ameliorating oxidative stress. The majority (15) of the 18 sea anemone GSTs are readily classifiable, including 3 mu-class, 3 omega-class, 6 sigma-class, 1 theta-class, 1 fungal-type, and 1 zeta-class. The 3 remaining GSTs appear hom*ologous to the xenobiotic-metabolizing alpha/pi GSTs. This search also found a sequence hom*ologous to the translation elongation factor 1g (EF1g), which contains a GST domain but does not have glutathione transferase activity. The N. vectensis genome also codes for a total of 5 microsomal GST (MAPEG) sequences, including 1 hom*ologous to vertebrate MAPEG1, 1 sequence hom*ologous to MAPEG3, and 3 sequences hom*ologous to prostaglandin E synthase (PTGS). PTGS enzymes are MAPEG superfamily members important to eicosanoid synthesis and involved in the vertebrate inflammation response (Jakobsson et al, 1999). Prostaglandins in corals are very important in chemical defense [reviewed in (Paul and Puglisi, 2004; Paul et al, 2006)] and have been extensively studied in gorgonians. A prostaglandin synthase with 50% identity to mammalian PTGS has been cloned from an Arctic soft coral (Koljak et al, 2001).

SULT and UGT enzymes catalyze the conjugation of sulfuryl groups donated by 3'-phosphoadenosine-5'-phosphosulfate (PAPS) or UDP-glucuronide, respectively, to a wide variety of substrates, including both xenobiotics and endogenous products (Bock and Kohle, 2004; Gamage et al, 2006; Runge-Morris and Kocarek, 2005). Cytosolic (soluble) SULTs are responsible for the metabolism of xenobiotic and small endogenous substrates (SULT1 and SULT2), while membrane-bound SULTs are involved in endogenous peptide, lipid, and aminosugar sulfonation (Gamage et al, 2006). I found 22 SULT genes in the sea anemone genome, all of which are more closely related to the SULT genes involved in energy metabolism rather than those SULT genes known from vertebrate studies to participate in detoxification reactions. The anemone genes are divided among the SULT3A family (8 genes), SULT3B (2 genes), SULT4 (4 genes), and carbohydrate keratan/chondroitin SULTs (8 genes). Chondroitin sulfation has been demonstrated in the nematocysts of Hydra magnipapillata (Yamada et al, 2007), and it is possible that the N. vectensis genes are involved in similar functions.

The sea anemone UGT genes are likewise not closely related to the UGT families with known xenobiotic metabolizing or detoxification roles. UGT1 genes in mammals consist of one gene with as many as 14 different first exons, complicating the assignment of UGT hom*ology (Mackenzie et al, 2005). Based on our previous analysis of the large number of distinct genes in the sea urchin, exon duplication like that observed in the mammalian UGT families is not the only method of UGT diversification. However, the 9 anemone UGTs are not classifiable to any of the known vertebrate UGT families, and thus no function can even be hinted at. This finding is not unique to anemones, as other marine genomes contain what appear to be lineage-specific gene family expansions that are not readily assignable to known UGT functional classes (J. Goldstone, unpublished data).

Antioxidant proteins

Reactive oxygen species (ROS), including superoxide, hydrogen peroxide, and hydroxyl radicals, are derived from a variety of cellular processes, including leakage from mitochondrial respiration. Reactive oxygen can also be produced by exposure to toxicants and to ultraviolet radiation. ROS contribute to diseases and pathologies generally deriving from altered gene expression or damage to biomolecules, including proteins, lipids and DNA (Halliwell and Gutteridge, 1999; Lesser, 2006). General antioxidant defensive genes include superoxide dismutase (SOD), catalases (CAT), and peroxidases, including glutathione peroxidase (GPX), peroxiredoxin (PRDX) and thioredoxins (TXNs).

The sea anemone genome has a total of 6 superoxide dismutase (SOD) genes: 3 Cu/Zn SOD genes, 1 Mn SOD gene, 2 Fe SODs, as well as an SOD copper chaperone hom*olog (which contains an SOD domain but has no dismutase activity). Both EST and cDNA libraries support the expression of all 6 SOD forms under normal conditions (A. Reitzel, A. Tarrant, J. Goldstone unpublished data). In addition, there is one catalase (CAT), 12 glutathione peroxidase genes, and 6 other heme peroxidase genes. This abundance of antioxidant defense genes is complemented by a complete glutathione system (glutathione reductase and 4 gamma-glutamyl transferases), as well as thioredoxin (TXN) and thioredoxin reductase (TXNRD).

Metal detoxification

Heavy metals are important aquatic pollutants resulting from sewage, urban and agricultural runoff, and antifouling paint. Bioconcentration of heavy metals can lead to tissue concentrations that are 10 to 10 000-fold higher than environmental levels, resulting in a variety of toxic effects. Four phytochelatin synthase (PCS) hom*ologs are present in the N. vectensis genome, and expressed under normal conditions (A. Reitzel, A. Tarrant, J. Goldstone unpublished data). Phytochelatins are metal-binding peptides composed primarily of glutathione groups that are important metal detoxifying genes in plants and fungi. Until phytochelatin synthase (PCS) was discovered in the nematode C. elegans (Clemens et al, 2001) it was believed that phytochelatins were present only in plants and fungi. Now it is clear that many other lineages contain PCS hom*ologs (Clemens, 2006), including the sea urchin (Goldstone et al, 2006). Currently sequenced vertebrate genomes do not contain a gene hom*ologous to PCS, nor do insect genomes, suggesting that phytochelatin synthesis ability was lost independently in some protostome and deuterostome lineages.

No metallothionein (MT) genes, neither plant- nor fungi- nor metazoan-related, were found in the sea anemone genome despite extensive searching, perhaps because of the presence of the alternative metal-complexing phytochelatin system. The absence of MT genes is apparently due to gene loss, as MT proteins are important metal detoxification proteins in plants (Cobbett and Goldsbrough, 2002), mollusks (Amiard et al, 2006), sea urchins (Nemer et al, 1985), and vertebrates, and are also present in sponges (Berthet et al, 2005; Philp, 1999).

Active efflux of toxic metals is another important route to detoxification. Both OAT and ABC efflux proteins (see above) export metals (Leslie et al, 2001; Sweet, 2005), and the anemone contains genes hom*ologous to the transporters (within both the OAT and ABC families) known to facilitate metal export.

Heat Shock Proteins

Heat shock proteins (HSP) have been implicated in the response to various toxicants including cadmium, arsenic, and free radicals (Feder and Hofmann, 1999). The induction of HSP mRNA and protein by heat shock factor 1 (HSF1) appears to be part of generalized cellular stress response, and HSPs may not only act as chaperones but also assist in refolding of partially denatured proteins (Kim et al, 2006). Sea anemones have several families of heat shock proteins including HSP 90, 70, and small alpha crystalline HSPs (HSP20s). The largest family of heat shock proteins is the HSP20 family, containing at least 18 genes. Sea anemones also have at least 4 HSP90 genes and 9 HSP70s. Various coral and anemone HSP60, HSP70, and HSP90 proteins and cDNA sequences have been shown to be strongly induced not only by heat or cold shock (Choresh et al, 2007; Choresh et al, 2004; Choresh et al, 2001; Hashimoto et al, 2004; Robbart et al, 2004; Rossi and Snyder, 2001; Rossi et al, 2006; Sharp et al, 1997; Sharp et al, 1994; Snyder and Ross, 2004), but also by PCB118 (Wiens et al, 2000).

Signaling Network

Ligand activated transcription factors form a significant component of the defensome, integrating the stress response and potentially activating many different pathways simultaneously. The evolutionary history of both the bZIP (Amoutzias et al, 2007) and bHLH-PAS (Simionato et al, 2007) receptor superfamilies is complicated, but most major clades of these receptors are present in cnidaria. Although some of the known components of the vertebrate and invertebrate xenobiotic receptor pathways are missing, hom*ologs of most important stress receptors are present, including AHR, ARNT, HIF1α, MTF, and NRF2. The deuterostome xenobiotic-responsive NR1H and NR1I subfamilies are missing, however, and it is not currently known whether other NRs are functioning as xenobiotic receptors. Cnidaria have been shown to have a retinoid response, including a functional hom*olog of the RXR (Bouzaiene et al, 2007; Johnson and Chun, 1989; Kostrouch et al, 1998; Muller, 1984).

Gene Family Diversification

Many defense gene families have undergone diversification and expansion in marine invertebrates in comparison to vertebrate genomes. In general, analysis of entire genomes is required to determine that a specific family or superfamily has undergone diversification, and thus current examples of such events is scattered. Class or order level diversification may be presumed, based on the model organisms with sequenced genomes, but caution should be exercised when extrapolating. Although there is general conformity in the presence of higher order gene groups, in many cases gene orthology is more difficult to determine.

For example, the sea anemone contains 82 CYP genes, and those related to CYP gene families 1–4 constitute a large proportion (76%) of the total, suggesting evolutionary pressure to maintain broad functionality in these important defense gene families. Multiple gene duplications in the toxicologically important CYP families appear to have taken place in many different lineages, leading to taxon-specific gene clades that are related to known CYP families yet distinct enough to preclude definitive assignment of names based on current CYP nomenclature guidelines. The extensive birth-death process of CYP diversification is not solely represented by invertebrates – within the vertebrates there is significant evidence for extensive gene duplication and loss within xenobiotic-metabolizing CYP families (Thomas, 2007).

In N. vectensis, particular examples of family diversification relative to known sequences are the CYPs and the ABC transporters. Other defensome gene families do not appear significantly expanded, nor do they have genes distributed into completely novel subfamilies. This observation is interesting in light of the fact that N. vectensis lives in the challenging environment of a temperate estuary, and ranges from subtropical to subarctic estuaries (Hand and Uhlinger, 1994).

Symbiosis

An important consideration for the study of cnidarian chemical defense genes is that many species are host to photosynthetic endosymbionts (zooxanthellae or zoochorellae). There are unique aspects of both normal physiology and toxicological responses that are related to the presence of endosymbionts. Notably, photosynthesis produces oxygen, and surrounding host tissues require additional protection against ROS to withstand hyperoxygenation, such as additional superoxide dismutase genes. Indeed, Allemand and coworkers have characterized multiple SOD forms in the Mediterranean sea anemone Anemone viridis. They found up to seven SOD activity bands in various tissues, and detected several forms of CuZnSOD, MnSOD, and FeSOD in the various compartments (Richier et al, 2003). Two of the CuZnSODs were cloned, and encode both extracellular and intracellular CuZnSODs with different putative transcription binding sites (Plantivaux et al, 2004).

Although N. vectensis is an apparently asymbiotic anemone, the genome has genes for 6 different SODs, all of which are expressed under normal conditions. This abundance of SOD genes may be a general pattern, particularly in anthozoans. Interestingly, greater diversity in SOD activities was found in the symbiotic anemone species (A. viridis) than in an asymbiotic species (Actinia schmidti), and the asymbiotic anemone experienced significantly greater oxidative protein damage upon exposure to hyperoxia (Richier et al, 2005). Thus, the presence of photosynthetic endosymbionts and the concomitant possibility of hyperoxia may have driven the evolution of multiple additional SOD forms in cnidaria. Several different catalase forms were also characterized in A. viridis, with tissue-specific distributions and activities (Merle et al, 2007). Inhibition of the host anemone catalase led to symbiont expulsion, suggesting an active response to increased oxidative stress.

A second effect of algal symbiosis is the sensitivity of symbiotic cnidarian species to herbicidal contamination (Jones, 2005; Jones and Kerswell, 2003). Notably, there is increasing distribution of herbicides such as the s-triazine Irgarol 1051 that have been incorporated into marine anti-fouling paints along with copper (Carbery et al, 2006; Gardinali et al, 2004), and there is significant runoff of herbicide-containing waste from agricultural regions. Irgarol 1051 is a photosystem II binding agent that inhibits photosynthetic electron transport, resulting in a shortage of NADPH and the formation of singlet oxygen (Fufezan et al, 2002). Acute exposure of coral to Irgarol 1051 resulted in induction of SOD and MXR (ABCG) proteins and decreases of GPX, CAT, and certain CYP proteins (Downs and Downs, 2007). While other herbicides have been investigated (e.g diuron (Harrington et al, 2005; Negri et al, 2005; Raberg et al, 2003)), there have been relatively few investigations of the molecular mechanisms of herbicide toxicity in cnidaria, and it is generally thought that damage is primarily a result of the disruption of host-algal symbiosis (Jones, 2005).

Reactive oxygen and UV

ROS production can also be an important consequence of UV exposure (Lesser, 2006; Mopper and Kieber, 2000). While UV responses have been studied in a number of coral species, many coral physiological responses to UV appear to be related to the physiological responses of their algal symbionts (Baruch et al, 2005; Torres et al, 2007; Verde and McCloskey, 2002). UV has been shown to interfere with pattern formation in regenerating hydra and promote budding of intact hydra, possibly in response to tissue damage (Ghaskadbi et al, 2005; Znidaric et al, 1992). Both exogenous hydrogen peroxide and UV treatments have been shown to increase DNA strand breaks in cnidaria, demonstrating the potential for genotoxic ROS effects (Baruch et al, 2005; Mitchelmore and Hyatt, 2004)

A very important protective mechanism in corals, as well as in diverse other marine organisms, is the accumulation of sunscreening compounds known as mycosporine-like amino acids (MAAs; (Shick and Dunlap, 2002)). MAAs may facilitate larval survival (Wellington and Fitt, 2003) as well as adult UV tolerance (Ferrier-Pages et al, 2007; Torres et al, 2007), and may also contribute to antioxidant capacity (Dunlap and Yamamoto, 1995; Yakovleva et al, 2004). In contrast to other animals, N. vectensis apparently possesses the shikimic acid pathway thought to be necessary for MAA production (Starcevic et al, 2008), presumably obtained via lateral gene transfer from bacteria. Many cnidaria have been thought to accumulate MAAs from their symbionts (Shick and Dunlap, 2002), or from their diet, as is the case for sea urchins (Carroll and Shick, 1996). Given the presence of the MAA biosynthetic pathway in the N. vectensis genome, and the clustering of sea anemone MAA complement by anemone phylogenetic distribution rather than endosymbiont identity, presence, or other environmental factors (Shick et al, 2002), it is likely that the ability of cnidaria to biosynthesize MAAs is not restricted to N. vectensis.

In contrast to tropical corals and many littoral anemones, N. vectensis is a burrowing anemone, and it is possible that N. vectensis adult may be able to avoid UV damage despite living in shallow ponds. However, larval N. vectensis may require more protection from ROS than adults, leading to the apparent diversification of ROS defenses. Examination of the UV-stress response of N. vectensis will aid in understanding the different roles that antioxidant enzymes and sunscreening compounds may play in protecting sea anemones. Comparisons of N. vectensis, an apparently asymbiotic anemone, with symbiotic anemones (e.g. A. viridis) or symbiotic reef-building corals could elucidate the protective mechanisms required by symbiotic cnidaria, and shed light on the role of antioxidant enzymes in thermotolerance and bleaching (Downs et al, 2002; Merle et al, 2007; Richier et al, 2005; Richier et al, 2003).

Molecular Toxicology

Many toxicological studies of cnidaria involve metals, particularly copper, cadmium, and zinc. In particular, the acute and structural effects of copper, cadmium, and zinc have been investigated in various hydrozoan species, including both freshwater and marine hydra (Holdway et al, 2001; Karntanut and Pascoe, 2000, 2002, 2005) and a variety of anthozoa, including scleractinian corals (Mitchelmore et al, 2007). Other biological responses to heavy metals in cnidaria include coral bleaching (Jones, 1997), and effects on coral metabolism (Alutoin et al, 2001; Nystrom et al, 2001), larval mortality, and inhibition of reproduction including settlement, motility and fertilization of larvae (Negri and Heyward, 2000, 2001; Reichelt-Brushett and Harrison, 2000, 2005). Few studies have examined molecular biomarkers or molecular mechanisms of metal stress (Mitchelmore et al, 2002; Morgan et al, 2001).

The availability of the N. vectensis genome will make many mechanistic studies possible, and should spur the development of metal stress biomarkers in various species. In particular, the presence of multiple genes for phytochelatin synthase provides obvious markers for metal stress, despite the lack of metalothionein genes.

As with metal contamination, there are few studies of either molecular markers or mechanisms of exposure to organic contaminants other than herbicides in cnidaria (Rougee et al, 2006). A number of biochemical studies of cnidarian CYP biochemistry have been carried out, however. CYP carbon monoxide difference spectra have been observed in six different species of sea anemone (Heffernan and Winston, 1998, 2000; Sole and Livingstone, 2005) and three different species of scleractinian corals [Favia fragum, Siderastrea sidea, and Montastraea faveolata; (Garcia et al, 2005; Gassman and Kennedy, 1992; Ramos and Garcia, 2007)]. Furthermore, benzo[a]pyrene hydroxylase activities have been observed in sea anemones, likely due to the action of CYP mixed-function oxygenases (Heffernan et al, 1996; Winston et al, 1998). The presence of inducible (versus constituent) CYP content in corals has also been demonstrated in coral due to benzo[a]pyrene or fuel oil exposure (Ramos and Garcia, 2007; Rougee et al, 2006). The same PAH exposures induced components of the reactive oxygen defense systems, including CAT, SOD, and GST. Finally, an important molecular marker of genotoxic damage, the Comet assay of DNA damage, has been assessed in cnidaria in response to benzo[a]pyrene exposures (Mitchelmore and Hyatt, 2004). Benzo[a]pyrene was found to increase DNA strand breaks in the temperate anemone Anthopleura elegantissima, suggesting also that cnidaria, like vertebrates, are capable of bioactivating benzo[a]pyrene to genotoxic metabolites, likely by CYPs.

More subtle effects of organic contamination might include in particular disruption of endogenous signaling pathways by exogenous hormones or hormone mimetics. Recent research indicates that cnidaria are susceptible to this sort of signal disruption, although the precise mechanisms are unknown (f*ckuhori et al, 2005; Pachura-Bouchet et al, 2006; Pascoe et al, 2002; Tarrant, 2005, 2007; Tarrant et al, 2004). In particular, Tarrant et al (2004) observed that spawning and growth rates were reduced in corals exposed to exogenous steroidal estrogens. As noted above, cnidaria do not posses a hom*olog of the vertebrate estrogen receptor, although there may be other nuclear receptors that function as a steroid receptors (Reitzel et al, 2008; Tarrant, 2007). Cnidaria are steroid-rich organisms (Withers et al, 1982), but the roles these steroids play in normal physiology are not clear (Tarrant, 2005). Steroids and secosteroids from gorgonian and soft corals have been show to have antimicrobial and antifouling activity (Qi et al, 2008; Sica and Musumeci, 2004), suggesting that many of these compounds may be produced for chemical defense. CYP enzymes often participate in steroid synthesis and modification, and the diversity of N. vectensis CYPs may relate to the diversity of cnidarian steroids, although the steroid content of N. vectensis has not been investigated.

N. vectensis is a physical stress-tolerant organism, tolerating a wide range of environmental conditions (Sheader et al, 1997). With this robustness to physical stress, N. vectensis is in a prime position to act as a sentinel species towards chemical stress in estuaries. N. vectensis is also an excellent laboratory model, with simple maintenance needs, and the generation of clonal stocks by forced regeneration allows great scope for genetic manipulation. Furthermore, this sea anemone is an excellent model for the study of embryonic development (Matus et al, 2006). With the description of these chemical defense genes, we can study of the evolution of cellular defense during embryonic development. Development inherently is a robust process; which parts of the process are more susceptible to disruption, and from which stressors, is not clear (Hamdoun and Epel, 2007). The description of this defense gene set will allow us to examine the evolution of generalized cellular stress responses in bilaterian embryos and to understand how these stress responses function in adult cnidaria.

2

• Allikmets R, Schriml LM, Hutchinson A, Romano-Spica V, Dean M. A human placenta-specific ATP-binding cassette gene (ABCP) on chromosome 4q22 that is involved in multidrug resistance. Cancer Res. 1998;58(23):5337–5339. [PubMed] [Google Scholar]
• Alutoin S, Boberg J, Nystrom M, Tedengren M. Effects of the multiple stressors copper and reduced salinity on the metabolism of the hermatypic coral Porites lutea. Marine environmental research. 2001;52(3):289–299. [PubMed] [Google Scholar]
• Amiard JC, Amiard-Triquet C, Barka S, Pellerin J, Rainbow PS. Metallothioneins in aquatic invertebrates: their role in metal detoxification and their use as biomarkers. Aquat Toxicol. 2006;76(2):160–202. [PubMed] [Google Scholar]
• Amoutzias GD, Veron AS, Weiner J, 3rd, Robinson-Rechavi M, Bornberg-Bauer E, Oliver SG, et al. One billion years of bZIP transcription factor evolution: conservation and change in dimerization and DNA-binding site specificity. Mol Biol Evol. 2007;24(3):827–835. [PubMed] [Google Scholar]
• Annilo T, Chen ZQ, Shulenin S, Costantino J, Thomas L, Lou H, et al. Evolution of the vertebrate ABC gene family: Analysis of gene birth and death. Genomics. 2006 [PubMed] [Google Scholar]
• Arkhipchuk VV, Blaise C, Malinovskaya MV. Use of hydra for chronic toxicity assessment of waters intended for human consumption. Environ Pollut. 2006;142(2):200–211. [PubMed] [Google Scholar]
• Atkinson S, Atkinson MJ. Detection of Estradiol-17-Beta during a Mass Coral Spawn. Coral Reefs. 1992;11(1):33–35. [Google Scholar]
• Baruch R, Avishai N, Rabinowitz C. UV incites diverse levels of DNA breaks in different cellular compartments of a branching coral species. Journal of Experimental Biology. 2005;208(5):843–848. [PubMed] [Google Scholar]
• Berthet B, Mouneyrac C, Perez T, Amiard-Triquet C. Metallothionein concentration in sponges (Spongia officinalis) as a biomarker of metal contamination. Comp Biochem Physiol C Toxicol Pharmacol. 2005;141(3):306–313. [PubMed] [Google Scholar]
• Blank V. Small Maf proteins in mammalian gene control: mere dimerization partners or dynamic transcriptional regulators? J Mol Biol. 2008;376(4):913–925. [PubMed] [Google Scholar]
• Blomquist CH, Lima PH, Tarrant AM, Atkinson MJ, Atkinson S. 17Beta-hydroxysteroid dehydrogenase (17beta-HSD) in scleractinian corals and zooxanthellae. Comp Biochem Physiol B Biochem Mol Biol. 2006;143(4):397–403. [PubMed] [Google Scholar]
• Bock KW, Kohle C. Coordinate regulation of drug metabolism by xenobiotic nuclear receptors: UGTs acting together with CYPs and glucuronide transporters. Drug Metab Rev. 2004;36(3–4):595–615. [PubMed] [Google Scholar]
• Bouzaiene M, Angers A, Anctil M. Immunohistochemical localization of a retinoic acid-like receptor in nerve cells of two colonial anthozoans (Cnidaria) Tissue & cell. 2007;39(2):123–130. [PubMed] [Google Scholar]
• Bresell A, Weinander R, Lundqvist G, Raza H, Shimoji M, Sun TH, et al. Bioinformatic and enzymatic characterization of the MAPEG superfamily. The FEBS journal. 2005;272(7):1688–1703. [PubMed] [Google Scholar]
• Carbery K, Owen R, Frickers T, Otero E, Readman J. Contamination of Caribbean coastal waters by the antifouling herbicide Irgarol 1051. Mar Pollut Bull. 2006;52(6):635–644. [PubMed] [Google Scholar]
• Carroll AK, Shick JM. Dietary accumulation of UV-absorbing mycosporine-like amino acids (MAAs) by the green sea urchin (Strongylocentrotus droebachiensis) Marine Biology. 1996;124(4):561–569. [Google Scholar]
• Cashman JR. Some distinctions between flavin-containing and cytochrome P450 monooxygenases. Biochem Biophys Res Commun. 2005;338(1):599–604. [PubMed] [Google Scholar]
• Castro LF, Santos MM, Reis-Henriques MA. The genomic environment around the Aromatase gene: evolutionary insights. BMC evolutionary biology. 2005;5:43. [PMC free article] [PubMed] [Google Scholar]
• Choresh O, Azem A, Loya Y. Over-expression of highly conserved mitochondrial 70-kDa heat-shock protein in the sea anemone Anemonia viridis. Journal of Thermal Biology. 2007;32(7–8):367–373. [Google Scholar]
• Choresh O, Loya Y, Muller WE, Wiedenmann J, Azem A. The mitochondrial 60-kDa heat shock protein in marine invertebrates: biochemical purification and molecular characterization. Cell stress & chaperones. 2004;9(1):38–48. [PMC free article] [PubMed] [Google Scholar]
• Choresh O, Ron E, Loya Y. The 60-kDa heat shock protein (HSP60) of the sea anemone Anemonia viridis: A potential early warning system for environmental changes. Marine Biotechnology. 2001;3(5):501–508. [PubMed] [Google Scholar]
• Clemens S. Evolution and function of phytochelatin synthases. J Plant Physiol. 2006;163(3):319–332. [PubMed] [Google Scholar]
• Clemens S, Schroeder JI, Degenkolb T. Caenorhabditis elegans expresses a functional phytochelatin synthase. Eur J Biochem. 2001;268(13):3640–3643. [PubMed] [Google Scholar]
• Cobbett C, Goldsbrough P. Phytochelatins and metallothioneins: roles in heavy metal detoxification and homeostasis. Annual review of plant biology. 2002;53:159–182. [PubMed] [Google Scholar]
• Daly M. A systematic revision of Edwardsiidae (Cnidaria, Anthozoa) Invertebrate Biology. 2002;121(3):212–225. [Google Scholar]
• Darling JA, Reitzel AR, Burton PM, Mazza ME, Ryan JF, Sullivan JC, et al. Rising starlet: the starlet sea anemone, Nematostella vectensis. Bioessays. 2005;27(2):211–221. [PubMed] [Google Scholar]
• Davidson EH, Erwin DH. Gene regulatory networks and the evolution of animal body plans. Science. 2006;311(5762):796–800. [PubMed] [Google Scholar]
• Davies WJ, Freeman SJ. Methods in molecular biology. Vol. 43. Clifton, NJ: 1995. The Hydra attenuata assay; pp. 321–326. [PubMed] [Google Scholar]
• de Jong DM, Hislop NR, Hayward DC, Reece-Hoyes JS, Pontynen PC, Ball EE, et al. Components of both major axial patterning systems of the Bilateria are differentially expressed along the primary axis of a 'radiate' animal, the anthozoan cnidarian Acropora millepora. Dev Biol. 2006;298(2):632–643. [PubMed] [Google Scholar]
• Dean M, Annilo T. Evolution of the ATP-binding cassette (ABC) transporter superfamily in vertebrates. Annu Rev Genomics Hum Genet. 2005;6:123–142. [PubMed] [Google Scholar]
• Dean M, Fojo T, Bates S. Tumour stem cells and drug resistance. Nat Rev Cancer. 2005;5(4):275–284. [PubMed] [Google Scholar]
• Dean M, Hamon Y, Chimini G. The human ATP-binding cassette (ABC) transporter superfamily. J Lipid Res. 2001;42(7):1007–1017. [PubMed] [Google Scholar]
• Deeley RG, Westlake C, Cole SP. Transmembrane transport of endo- and xenobiotics by mammalian ATP-binding cassette multidrug resistance proteins. Physiological reviews. 2006;86(3):849–899. [PubMed] [Google Scholar]
• Downs C, Downs A. Preliminary examination of short-term cellular toxicological responses of the coral Madracis mirabilis to acute Irgarol 1051 exposure. Archives of environmental contamination and toxicology. 2007;52(1):47–57. [PubMed] [Google Scholar]
• Downs CA, Fauth JE, Halas JC, Dustan P, Bemiss J, Woodley CM. Oxidative stress and seasonal coral bleaching. Free Radic Biol Med. 2002;33(4):533–543. [PubMed] [Google Scholar]
• Dunlap WC, Yamamoto Y. Small-molecule antioxidants in marine organisms: antioxidant activity of mycosporine-glycine. Comp Biochem PhysiolComp Biochem Physiol B. 1995;112(1):105–114. [Google Scholar]
• Dunn CW, Hejnol A, Matus DQ, Pang K, Browne WE, Smith SA, et al. Broad phylogenomic sampling improves resolution of the animal tree of life. Nature. 2008;452(7188):745–749. [PubMed] [Google Scholar]
• Eddy SR. Profile hidden Markov models. Bioinformatics. 1998;14:755–763. [PubMed] [Google Scholar]
• Edgar RC. MUSCLE: multiple sequence alignment with high accuracy and high throughput. Nucleic Acids Res. 2004;32(5):1792–1797. [PMC free article] [PubMed] [Google Scholar]
• Epel D. Protection of DNA during early development: adaptations and evolutionary consequences. Evol Dev. 2003;5(1):83–88. [PubMed] [Google Scholar]
• Eraly SA, Monte JC, Nigam SK. Novel slc22 transporter hom*ologs in fly, worm, and human clarify the phylogeny of organic anion and cation transporters. Physiological genomics. 2004;18(1):12–24. [PubMed] [Google Scholar]
• Ferrier-Pages C, Richard C, Forcioli D, Allemand D, Pichon M, Shick JM. Effects of temperature and UV radiation increases on the photosynthetic efficiency in four scleractinian coral species. The Biological bulletin. 2007;213(1):76–87. [PubMed] [Google Scholar]
• Finkel T, Holbrook NJ. Oxidants, oxidative stress and the biology of ageing. Nature. 2000;408(6809):239–247. [PubMed] [Google Scholar]
• Finnerty JR, Martindale MQ. Ancient origins of axial patterning genes: Hox genes and ParaHox genes in the Cnidaria. Evol Dev. 1999;1(1):16–23. [PubMed] [Google Scholar]
• Finnerty JR, Pang K, Burton P, Paulson D, Martindale MQ. Origins of bilateral symmetry: Hox and dpp expression in a sea anemone. Science. 2004;304(5675):1335–1337. [PubMed] [Google Scholar]
• Fritzenwanker JH, Saina M, Technau U. Analysis of forkhead and snail expression reveals epithelial-mesenchymal transitions during embryonic and larval development of Nematostella vectensis. Dev Biol. 2004;275(2):389–402. [PubMed] [Google Scholar]
• Fufezan C, Rutherford AW, Krieger-Liszkay A. Singlet oxygen production in herbicide-treated photosystem II. FEBS letters. 2002;532(3):407–410. [PubMed] [Google Scholar]
• f*ckuhori N, Kitano M, Kimura H. Toxic effects of bisphenol A on sexual and asexual reproduction in Hydra oligactis. Archives of environmental contamination and toxicology. 2005;48(4):495–500. [PubMed] [Google Scholar]
• Gamage N, Barnett A, Hempel N, Duggleby RG, Windmill KF, Martin JL, et al. Human sulfotransferases and their role in chemical metabolism. Toxicol Sci. 2006;90(1):5–22. [PubMed] [Google Scholar]
• Garcia E, Ramos R, Bastidas C. Presence of cytochrome P450 in the Carribean corals Siderastrea siderea and Motastaea faveolata. Cinenc Mar. 2005;31:1–7. [Google Scholar]
• Gardinali PR, Plasencia MD, Maxey C. Occurrence and transport of Irgarol 1051 and its major metabolite in coastal waters from South Florida. Mar Pollut Bull. 2004;49(11–):11–12. [PubMed] [Google Scholar]
• Gassman NJ, Kennedy CJ. Cytochrome P450 content and xenobiotic metabolizing enzyme activities in the scleractinian coral, Favia fragum (ESPER) Bull Mar Sci. 1992;50:320–330. [Google Scholar]
• Ghaskadbi SS, Shetye L, Chiplonkar S, Ghaskadbi S. Ultraviolet irradiation initiates ectopic foot formation in regenerating hydra and promotes budding. Journal of biosciences. 2005;30(2):177–182. [PubMed] [Google Scholar]
• Goldstone J, Hamdoun AM, Cole B, Ashby MH, Scally M, Dean M, et al. The chemical defensome: Environmental sensing and response genes in the Strongylocentrotus purpuratus genome. Dev Biol. 2006;300(1):366–384. [PMC free article] [PubMed] [Google Scholar]
• Goldstone JV, Goldstone HM, Morrison AM, Tarrant A, Kern SE, Woodin BR, et al. Cytochrome P450 1 Genes in Early Deuterostomes (Tunicates and Sea Urchins) and Vertebrates (Chicken and Frog): Origin and Diversification of the CYP1 Gene Family. Mol Biol Evol. 2007;24(12):2619–2631. [PubMed] [Google Scholar]
• Grasso LC, Hayward DC, Trueman JW, Hardie KM, Janssens PA, Ball EE. The evolution of nuclear receptors: evidence from the coral Acropora. Mol Phylogenet Evol. 2001;21(1):93–102. [PubMed] [Google Scholar]
• Guengerich FP, McCormick WA, Wheeler JB. Analysis of the kinetic mechanism of haloalkane conjugation by mammalian theta-class glutathione transferases. Chem Res Toxicol. 2003;16(11):1493–1499. [PubMed] [Google Scholar]
• Hagenbuch B, Meier PJ. The superfamily of organic anion transporting polypeptides. Biochim Biophys Acta. 2003;1609(1):1–18. [PubMed] [Google Scholar]
• Halliwell B, Gutteridge JMC. Free Radicals in Biology and Medicine. 3rd Edition ed. Oxford: Oxford University Press; 1999. [Google Scholar]
• Hamdoun A, Epel D. Embryo stability and vulnerability in an always changing world. Proc Natl Acad Sci U S A. 2007;104(6):1745–1750. [PMC free article] [PubMed] [Google Scholar]
• Hand C, Uhlinger K. The unique, widely distributed sea anemone, Nematostella vectensis Stephenson: A review, new facts, and questions. Estuaries. 1994;17:501–508. [Google Scholar]
• Harborne AR, Mumby PJ, Micheli F, Perry CT, Dahlgren CP, Holmes KE, et al. The functional value of Caribbean coral reef, seagrass and mangrove habitats to ecosystem processes. Advances in marine biology. 2006;50:57–189. [PubMed] [Google Scholar]
• Harrington L, Fabricius K, Eaglesham G, Negri A. Synergistic effects of diuron and sedimentation on photosynthesis and survival of crustose coralline algae. Mar Pollut Bull. 2005;51(1–4):415–427. [PubMed] [Google Scholar]
• Hashimoto K, Shibuno T, Murayama-Kayano E, Tanaka H, Kayano T. Isolation and characterization of stress-responsive genes from the scleractinian coral Pocillopora damicornis. Coral Reefs. 2004;23(4):485–491. [Google Scholar]
• Hayes JD, Flanagan JU, Jowsey IR. Glutathione transferases. Annu Rev Pharmacol Toxicol. 2005;45:51–88. [PubMed] [Google Scholar]
• Hecker M, Ullrich V. On the mechanism of prostacyclin and thromboxane A2 biosynthesis. J Biol Chem. 1989;264(1):141–150. [PubMed] [Google Scholar]
• Heffernan LM, Winston GW. Spectral analysis and catalytic activities of the microsomal mixed-function oxidase system of the sea anemone (phylum: Cnidaria) Comparative biochemistry and physiology. 1998;121(1–3):371–383. [PubMed] [Google Scholar]
• Heffernan LM, Winston GW. Distribution of microsomal CO-binding chromophores and EROD activity in sea anemone tissues. Marine environmental research. 2000;50(1–5):23–27. [PubMed] [Google Scholar]
• Heffernan LM, Zinn RR, Mayeaux MH, Winston GW. Benzo[a]pyrene metabolism in the sea anemone Bunodosoma cavernata. Faseb J. 1996;10(6):2868. [Google Scholar]
• Holdway DA, Lok K, Semaan M. The acute and chronic toxicity of cadmium and zinc to two hydra species. Environmental toxicology. 2001;16(6):557–565. [PubMed] [Google Scholar]
• Hyndman D, Bauman DR, Heredia VV, Penning TM. The aldo-keto reductase superfamily homepage. Chem Biol Interact. 2003:143–144. 621–631. [PubMed] [Google Scholar]
• Igarashi K, Sun J. The heme-Bach1 pathway in the regulation of oxidative stress response and erythroid differentiation. Antioxid Redox Signal. 2006;8(1–2):107–118. [PubMed] [Google Scholar]
• Jacobsson JA, Haitina T, Lindblom J, Fredriksson R. Identification of six putative human transporters with structural similarity to the drug transporter SLC22 family. Genomics. 2007;90(5):595–609. [PubMed] [Google Scholar]
• Jakobsson PJ, Thoren S, Morgenstern R, Samuelsson B. Identification of human prostaglandin E synthase: a microsomal, glutathione-dependent, inducible enzyme, constituting a potential novel drug target. Proc Natl Acad Sci U S A. 1999;96(13):7220–7225. [PMC free article] [PubMed] [Google Scholar]
• Jez JM, Penning TM. The aldo-keto reductase (AKR) superfamily: an update. Chem Biol Interact. 2001;130–132(1–3):499–525. [PubMed] [Google Scholar]
• Jin Y, Penning TM. Aldo-keto reductases and bioactivation/detoxication. Annu Rev Pharmacol Toxicol. 2007;47:263–292. [PubMed] [Google Scholar]
• Johnson EM, Chun YH. In vitro differential developmental toxicity of vitamin A congeners. Teratology. 1989;39(4):349–361. [PubMed] [Google Scholar]
• Jones R. The ecotoxicological effects of Photosystem II herbicides on corals. Mar Pollut Bull. 2005;51(5–7):495–506. [PubMed] [Google Scholar]
• Jones RJ. Zooxanthellae loss as a bioassay for assessing stress in corals. Marine Ecology-Progress Series. 1997;149(1–3):163–171. [Google Scholar]
• Jones RJ, Kerswell AP. Phytotoxicity of Photosystem II (PSII) herbicides to coral. Marine Ecology-Progress Series. 2003;261:149–159. [Google Scholar]
• Karntanut W, Pascoe D. A comparison of methods for measuring acute toxicity to Hydra vulgaris. Chemosphere. 2000;41(10):1543–1548. [PubMed] [Google Scholar]
• Karntanut W, Pascoe D. The toxicity of copper, cadmium and zinc to four different Hydra (Cnidaria: Hydrozoa) Chemosphere. 2002;47(10):1059–1064. [PubMed] [Google Scholar]
• Karntanut W, Pascoe D. Effects of removing symbiotic green algae on the response of Hydra viridissima (Pallas 1776) to metals. Ecotoxicology and environmental safety. 2005;60(3):301–305. [PubMed] [Google Scholar]
• Kewley RJ, Whitelaw ML, Chapman-Smith A. The mammalian basic helix-loop-helix/PAS family of transcriptional regulators. Int J Biochem Cell Biol. 2004;36(2):189–204. [PubMed] [Google Scholar]
• Kim HP, Morse D, Choi AM. Heat-shock proteins: new keys to the development of cytoprotective therapies. Expert opinion on therapeutic targets. 2006;10(5):759–769. [PubMed] [Google Scholar]
• Kimura H, Takeda M, Narikawa S, Enomoto A, Ichida K, Endou H. Human organic anion transporters and human organic cation transporters mediate renal transport of prostaglandins. The Journal of pharmacology and experimental therapeutics. 2002;301(1):293–298. [PubMed] [Google Scholar]
• Koljak R, Jarving I, Kurg R, Boeglin WE, Varvas K, Valmsen K, et al. The basis of prostaglandin synthesis in coral: molecular cloning and expression of a cyclooxygenase from the Arctic soft coral Gersemia fruticosa. J Biol Chem. 2001;276(10):7033–7040. [PubMed] [Google Scholar]
• Kostrouch Z, Kostrouchova M, Love W, Jannini E, Piatigorsky J, Rall JE. Retinoic acid X receptor in the diploblast, Tripedalia cystophora. Proc Natl Acad Sci U S A. 1998;95(23):13442–13447. [PMC free article] [PubMed] [Google Scholar]
• Kreil DP, Ouzounis CA. Comparison of sequence masking algorithms and the detection of biased protein sequence regions. Bioinformatics. 2003;19(13):1672–1681. [PubMed] [Google Scholar]
• Krueger SK, Williams DE. Mammalian flavin-containing monooxygenases: structure/function, genetic polymorphisms and role in drug metabolism. Pharmacology & therapeutics. 2005;106(3):357–387. [PMC free article] [PubMed] [Google Scholar]
• Kusserow A, Pang K, Sturm C, Hrouda M, Lentfer J, Schmidt HA, et al. Unexpected complexity of the Wnt gene family in a sea anemone. Nature. 2005;433(7022):156–160. [PubMed] [Google Scholar]
• Kusuhara H, Sugiyama Y. ATP-binding cassette, subfamily G (ABCG family) Pflugers Arch. 2007;453(5):735–744. [PubMed] [Google Scholar]
• Laity JH, Andrews GK. Understanding the mechanisms of zinc-sensing by metal-response element binding transcription factor-1 (MTF-1) Arch Biochem Biophys. 2007;463(2):201–210. [PubMed] [Google Scholar]
• Lee MO, Manthey CL, Sladek NE. Identification of mouse liver aldehyde dehydrogenases that catalyze the oxidation of retinaldehyde to retinoic acid. Biochem Pharmacol. 1991;42(6):1279–1285. [PubMed] [Google Scholar]
• Leslie EM, Deeley RG, Cole SP. Toxicological relevance of the multidrug resistance protein 1, MRP1 (ABCC1) and related transporters. Toxicology. 2001;167(1):3–23. [PubMed] [Google Scholar]
• Lesser MP. Oxidative stress in marine environments: biochemistry and physiological ecology. Annu Rev Physiol. 2006;68:253–278. [PubMed] [Google Scholar]
• Lewis DF, Lake BG, Dickins M. Substrates of human cytochromes P450 from families CYP1 and CYP2: analysis of enzyme selectivity and metabolism. Drug Metabol Drug Interact. 2004;20(3):111–142. [PubMed] [Google Scholar]
• Mackenzie PI, Walter Bock K, Burchell B, Guillemette C, Ikushiro S, Iyanagi T, et al. Nomenclature update for the mammalian UDP glycosyltransferase (UGT) gene superfamily. Pharmacogenet Genomics. 2005;15(10):677–685. [PubMed] [Google Scholar]
• Magie CR, Pang K, Martindale MQ. Genomic inventory and expression of Sox and Fox genes in the cnidarian Nematostella vectensis. Dev Genes Evol. 2005;215(12):618–630. [PubMed] [Google Scholar]
• Matus DQ, Pang K, Marlow H, Dunn CW, Thomsen GH, Martindale MQ. Molecular evidence for deep evolutionary roots of bilaterality in animal development. Proc Natl Acad Sci U S A. 2006;103(30):11195–11200. [PMC free article] [PubMed] [Google Scholar]
• Merle PL, Sabourault C, Richier S, Allemand D, Furla P. Catalase characterization and implication in bleaching of a symbiotic sea anemone. Free Radic Biol Med. 2007;42(2):236–246. [PubMed] [Google Scholar]
• Miller DJ, Hemmrich G, Ball EE, Hayward DC, Khalturin K, Funayama N, et al. The innate immune repertoire in cnidaria--ancestral complexity and stochastic gene loss. Genome biology. 2007;8(4):R59. [PMC free article] [PubMed] [Google Scholar]
• Mitchelmore CL, Hyatt S. Assessing DNA damage in cnidarians using the Comet assay. Marine environmental research. 2004;58(2–5):707–711. [PubMed] [Google Scholar]
• Mitchelmore CL, Schwarz JA, Weis VM. Development of symbiosis-specific genes as biomarkers for the early detection of cnidarian-algal symbiosis breakdown. Marine environmental research. 2002;54(3–5):345–349. [PubMed] [Google Scholar]
• Mitchelmore CL, Verde EA, Weis VM. Uptake and partitioning of copper and cadmium in the coral Pocillopora damicornis. Aquat Toxicol. 2007;85(1):48–56. [PubMed] [Google Scholar]
• Miyake K, Mickley L, Litman T, Zhan Z, Robey R, Cristensen B, et al. Molecular cloning of cDNAs which are highly overexpressed in mitoxantrone-resistant cells: demonstration of hom*ology to ABC transport genes. Cancer Res. 1999;59(1):8–13. [PubMed] [Google Scholar]
• Mizuta T, Kubokawa K. Presence of sex steroids and cytochrome P450 genes in amphioxus. Endocrinology. 2007;148(8):3554–3565. [PubMed] [Google Scholar]
• Mopper K, Kieber DJ. Marine photochemistry and its impacts on carbon cycling. In: De Mora S, Demers S, Vernet M, editors. The Effects of UV Radiation in the Marine Environment. Cambridge, UK: Cambridge University Press; 2000. pp. 101–130. [Google Scholar]
• Morgan MB, Vogelien DL, Snell TW. Assessing coral stress responses using molecular biomarkers of gene transcription. Environ Toxicol Chem. 2001;20(3):537–543. [PubMed] [Google Scholar]
• Muller WA. Retinoids and pattern formation in a hydroid. Journal of embryology and experimental morphology. 1984;81:253–271. [PubMed] [Google Scholar]
• Murphy BJ. Regulation of malignant progression by the hypoxia-sensitive transcription factors HIF-1alpha and MTF-1. Comp Biochem Physiol B Biochem Mol Biol. 2004;139(3):495–507. [PubMed] [Google Scholar]
• Murphy BJ, Andrews GK, Bittel D, Discher DJ, McCue J, Green CJ, et al. Activation of metallothionein gene expression by hypoxia involves metal response elements and metal transcription factor-1. Cancer Res. 1999;59(6):1315–1322. [PubMed] [Google Scholar]
• Murphy BJ, Sato BG, Dalton TP, Laderoute KR. The metal-responsive transcription factor-1 contributes to HIF-1 activation during hypoxic stress. Biochem Biophys Res Commun. 2005;337(3):860–867. [PubMed] [Google Scholar]
• Nebert DW, Vasiliou V. Analysis of the glutathione S-transferase (GST) gene family. Hum Genomics. 2004;1(6):460–464. [PMC free article] [PubMed] [Google Scholar]
• Negri A, Vollhardt C, Humphrey C, Heyward A, Jones R, Eaglesham G, et al. Effects of the herbicide diuron on the early life history stages of coral. Mar Pollut Bull. 2005;51(1–4):370–383. [PubMed] [Google Scholar]
• Negri AP, Heyward AJ. Inhibition of fertilization and larval metamorphosis of the coral Acropora millepora (Ehrenberg, 1834) by petroleum products. Mar Pollut Bull. 2000;41(7–12):420–427. [Google Scholar]
• Negri AP, Heyward AJ. Inhibition of coral fertilisation and larval metamorphosis by tributyltin and copper. Marine environmental research. 2001;51(1):17–27. [PubMed] [Google Scholar]
• Nelson DR. Metazoan cytochrome P450 evolution. Comparative biochemistry and physiology. 1998;121(1–3):15–22. [PubMed] [Google Scholar]
• Nelson DR. Methods in molecular biology. Vol. 320. Clifton, NJ: 2006. Cytochrome P450 nomenclature, 2004; pp. 1–10. [PubMed] [Google Scholar]
• Nelson DR, Kamataki T, Waxman DJ, Guengerich FP, Estabrook RW, Feyereisen R, et al. The P450 superfamily: update on new sequences, gene mapping, accession numbers, early trivial names of enzymes, and nomenclature. DNA Cell Biol. 1993;12(1):1–51. [PubMed] [Google Scholar]
• Nemer M, Wilkinson DG, Travaglini EC, Sternberg EJ, Butt TR. Sea urchin metallothionein sequence: key to an evolutionary diversity. Proc Natl Acad Sci U S A. 1985;82(15):4992–4994. [PMC free article] [PubMed] [Google Scholar]
• Nguyen T, Sherratt PJ, Huang HC, Yang CS, Pickett CB. Increased protein stability as a mechanism that enhances Nrf2-mediated transcriptional activation of the antioxidant response element. Degradation of Nrf2 by the 26 S proteasome. J Biol Chem. 2003;278(7):4536–4541. [PubMed] [Google Scholar]
• Nystrom M, Nordemar I, Tedengren M. Simultaneous and sequential stress from increased temperature and copper on the metabolism of the hermatypic coral Porites cylindrica. Marine Biology. 2001;138(6):1225–1231. [Google Scholar]
• Osburn WO, Kensler TW. Nrf2 signaling: an adaptive response pathway for protection against environmental toxic insults. Mutation research. 2008;659(1–2):31–39. [PMC free article] [PubMed] [Google Scholar]
• Pachura-Bouchet S, Blaise C, Vasseur P. Toxicity of nonylphenol on the cnidarian Hydra attenuata and environmental risk assessment. Environmental toxicology. 2006;21(4):388–394. [PubMed] [Google Scholar]
• Palackal NT, Burczynski ME, Harvey RG, Penning TM. Metabolic activation of polycyclic aromatic hydrocarbon trans-dihydrodiols by ubiquitously expressed aldehyde reductase (AKR1A1) Chem Biol Interact. 2001;130–132(1–3):815–824. [PubMed] [Google Scholar]
• Pascoe D, Carroll K, Karntanut W, Watts MM. Toxicity of 17alpha-ethinylestradiol and bisphenol A to the freshwater Cnidarian Hydra vulgaris. Archives of environmental contamination and toxicology. 2002;43(1):56–63. [PubMed] [Google Scholar]
• Paul VJ, Puglisi MP. Chemical mediation of interactions among marine organisms. Natural product reports. 2004;21(1):189–209. [PubMed] [Google Scholar]
• Paul VJ, Puglisi MP, Ritson-Williams R. Marine chemical ecology. Natural product reports. 2006;23(2):153–180. [PubMed] [Google Scholar]
• Penning TM, Burczynski ME, Hung CF, McCoull KD, Palackal NT, Tsuruda LS. Dihydrodiol dehydrogenases and polycyclic aromatic hydrocarbon activation: generation of reactive and redox active o-quinones. Chem Res Toxicol. 1999;12(1):1–18. [PubMed] [Google Scholar]
• Penning TM, Drury JE. Human aldo-keto reductases: Function, gene regulation, and single nucleotide polymorphisms. Arch Biochem Biophys. 2007;464(2):241–250. [PMC free article] [PubMed] [Google Scholar]
• Philp RB. Cadmium content of the marine sponge Microciona prolifera, other sponges, water and sediment from the eastern Florida panhandle: possible effects on Microciona cell aggregation and potential roles of low pH and low salinity. Comparative biochemistry and physiology. 1999;124(1):41–49. [PubMed] [Google Scholar]
• Plantivaux A, Furla P, Zoccola D, Garello G, Forcioli D, Richier S, et al. Molecular characterization of two CuZn-superoxide dismutases in a sea anemone. Free Radic Biol Med. 2004;37(8):1170–1181. [PubMed] [Google Scholar]
• Ponting CP. The functional repertoires of metazoan genomes. Nature reviews. 2008;9(9):689–698. [PubMed] [Google Scholar]
• Putnam NH, Srivastava M, Hellsten U, Dirks B, Chapman J, Salamov A, et al. Sea anemone genome reveals ancestral eumetazoan gene repertoire and genomic organization. Science. 2007;317(5834):86–94. [PubMed] [Google Scholar]
• Qi SH, Zhang S, Yang LH, Qian PY. Antifouling and antibacterial compounds from the gorgonians Subergorgia suberosa and Scripearia gracillis. Natural Product Research. 2008;22(2):154–166. [PubMed] [Google Scholar]
• Raberg S, Nystrom M, Eros M, Plantman P. Impact of the herbicides 2,4-D and diuron on the metabolism of the coral Porites cylindrica. Marine environmental research. 2003;56(4):503–514. [PubMed] [Google Scholar]
• Ramos R, Garcia E. Induction of mixed-function oxygenase system and antioxidant enzymes in the coral Montastraea faveolata on acute exposure to benzo(a)pyrene. Comp Biochem Physiol C Toxicol Pharmacol. 2007;144(4):348–355. [PubMed] [Google Scholar]
• Reichelt-Brushett AJ, Harrison PL. The effect of copper on the settlement success of larvae from the scleractinian coral Acropora tenuis. Mar Pollut Bull. 2000;41(7–12):385–391. [Google Scholar]
• Reichelt-Brushett AJ, Harrison PL. The effect of selected trace metals on the fertilization success of several scleractinian coral species. Coral Reefs. 2005;24(4):524–534. [Google Scholar]
• Reitzel AM, Darling JA, Sullivan JC, Finnerty JR. Global population genetic structure of the starlet anemone Nematostella vectensis: multiple introductions and implications for conservation policy. Biological Invasions. in press. [Google Scholar]
• Reitzel AM, Sullivan JC, Traylor-Knowles N, Finnerty JR. Genomic survey of candidate stress-response genes in the estuarine anemone Nematostella vectensis. The Biological bulletin. 2008;214(3):233–254. [PubMed] [Google Scholar]
• Richier S, Furla P, Plantivaux A, Merle PL, Allemand D. Symbiosis-induced adaptation to oxidative stress. J Exp Biol. 2005;208(Pt 2):277–285. [PubMed] [Google Scholar]
• Richier S, Merle PL, Furla P, Pigozzi D, Sola F, Allemand D. Characterization of superoxide dismutases in anoxia- and hyperoxia-tolerant symbiotic cnidarians. Biochim Biophys Acta. 2003;1621(1):84–91. [PubMed] [Google Scholar]
• Robbart ML, Peckol P, Scordilis SP, Curran HA, Brown-Saracino J. Population recovery and differential heat shock protein expression for the corals Agaricia agaricites and A-tenuifolia in Belize. Marine Ecology-Progress Series. 2004;283:151–160. [Google Scholar]
• Rossi S, Snyder MJ. Competition for space among sessile marine invertebrates: changes in HSP70 expression in two Pacific cnidarians. The Biological bulletin. 2001;201(3):385–393. [PubMed] [Google Scholar]
• Rossi S, Snyder MJ, Gili JM. Protein, carbohydrate, lipid concentrations and HSP70-HSP 90 (stress protein) expression over an annual cycle: useful tools to detect feeding constraints in a benthic suspension feeder. Helgoland Marine Research. 2006;60(1):7–17. [Google Scholar]
• Rougee L, Downs CA, Richmond RH, Ostrander GK. Alteration of normal cellular profiles in the scleractinian coral (Pocillopora damicornis) following laboratory exposure to fuel oil. Environ Toxicol Chem. 2006;25(12):3181–3187. [PubMed] [Google Scholar]
• Runge-Morris M, Kocarek TA. Regulation of sulfotransferases by xenobiotic receptors. Curr Drug Metab. 2005;6(4):299–307. [PubMed] [Google Scholar]
• Sebens KP. Recruitment in a Sea Anemone Population: Juvenile Substrate Becomes Adult Prey. Science. 1981;213(4509):785–787. [PubMed] [Google Scholar]
• Sharp VA, Brown BE, Miller D. Heat shock protein (hsp 70) expression in the tropical reef coral Goniopora djiboutiensis. Journal of Thermal Biology. 1997;22(1):11–19. [Google Scholar]
• Sharp VA, Miller D, Bythell JC, Brown BE. Expression of Low-Molecular-Weight Hsp-70 Related Polypeptides from the Symbiotic Sea-Anemone Anemonia-Viridis Forskall in Response to Heat-Shock. Journal of Experimental Marine Biology and Ecology. 1994;179(2):179–193. [Google Scholar]
• Sheader M, Suwailem A, Rowe G. The anemone, Nematostella vectensis, in Britain: Considerations for conservation management. Aquatic Conservation: Marine and Freshwater Ecosystems. 1997;7:13–25. [Google Scholar]
• Shick JM, Dunlap WC. Mycosporine-like amino acids and related Gadusols: biosynthesis, acumulation, and UV-protective functions in aquatic organisms. Annu Rev Physiol. 2002;64:223–262. [PubMed] [Google Scholar]
• Shick JM, Dunlap WC, Pearse JS, Pearse VB. Mycosporine-like amino acid content in four species of sea anemones in the genus Anthopleura reflects phylogenetic but not environmental or symbiotic relationships. The Biological bulletin. 2002;203(3):315–330. [PubMed] [Google Scholar]
• Shimada T. Xenobiotic-metabolizing enzymes involved in activation and detoxification of carcinogenic polycyclic aromatic hydrocarbons. Drug metabolism and pharmaco*kinetics. 2006;21(4):257–276. [PubMed] [Google Scholar]
• Sica D, Musumeci D. Secosteroids of marine origin. Steroids. 2004;69(11–12):743–756. [PubMed] [Google Scholar]
• Simionato E, Ledent V, Richards G, Thomas-Chollier M, Kerner P, Coornaert D, et al. Origin and diversification of the basic helix-loop-helix gene family in metazoans: insights from comparative genomics. BMC evolutionary biology. 2007;7:33. [PMC free article] [PubMed] [Google Scholar]
• Snyder MJ, Ross S. Stress protein (HSP70 family) expression in intertidal bentbic organisms: the example of Anthopleura elegantissima (Cnidaria : Anthozoa) Scientia Marina. 2004;68:155–162. [Google Scholar]
• Sole M, Livingstone DR. Components of the cytochrome P450-dependent monooxygenase system and 'NADPH-independent benzo[a]pyrene hydroxylase' activity in a wide range of marine invertebrate species. Comp Biochem Physiol C Toxicol Pharmacol. 2005;141(1):20–31. [PubMed] [Google Scholar]
• Stamatakis A. RAxML-VI-HPC: maximum likelihood-based phylogenetic analyses with thousands of taxa and mixed models. Bioinformatics. 2006;22(21):2688–2690. [PubMed] [Google Scholar]
• Starcevic A, Akthar S, Dunlap WC, Shick JM, Hranueli D, Cullum J, et al. Enzymes of the shikimic acid pathway encoded in the genome of a basal metazoan, Nematostella vectensis, have microbial origins. Proc Natl Acad Sci U S A. 2008 [PMC free article] [PubMed] [Google Scholar]
• Sullivan JC, Reitzel AM, Finnerty JR. Upgrades to StellaBase facilitate medical and genetic studies on the starlet sea anemone, Nematostella vectensis. Nucleic Acids Res. 2008;36(Database issue):D607–D611. [PMC free article] [PubMed] [Google Scholar]
• Surh YJ. Bioactivation of benzylic and allylic alcohols via sulfo-conjugation. Chem Biol Interact. 1998;109(1–3):221–235. [PubMed] [Google Scholar]
• Sweet DH. Organic anion transporter (Slc22a) family members as mediators of toxicity. Toxicol Appl Pharmacol. 2005;204(3):198–215. [PubMed] [Google Scholar]
• Tarrant AM. Endocrine-like signaling in cnidarians: current understanding and implications for ecophysiology. Integrative and Comparative Biology. 2005;45:201–214. [PubMed] [Google Scholar]
• Tarrant AM. Hormonal signaling in cnidarians: do we understand the pathways well enough to know whether they are being disrupted? Ecotoxicology (London, England) 2007;16(1):5–13. [PubMed] [Google Scholar]
• Tarrant AM, Atkinson MJ, Atkinson S. Effects of steroidal estrogens on coral growth and reproduction. Marine Ecology-Progress Series. 2004;269:121–129. [Google Scholar]
• Tarrant AM, Atkinson S, Atkinson MJ. Estrone and estradiol-17 beta concentration in tissue of the scleractinian coral, Montipora verrucosa. Comp Biochem Physiol A Mol Integr Physiol. 1999;122(1):85–92. [PubMed] [Google Scholar]
• Tarrant AM, Blomquist CH, Lima PH, Atkinson MJ, Atkinson S. Metabolism of estrogens and androgens by scleractinian corals. Comp Biochem Physiol B Biochem Mol Biol. 2003;136(3):473–485. [PubMed] [Google Scholar]
• Thomas JH. Rapid birth-death evolution specific to xenobiotic cytochrome P450 genes in vertebrates. PLoS genetics. 2007;3(5):e67. [PMC free article] [PubMed] [Google Scholar]
• Thornton JW, Need E, Crews D. Resurrecting the ancestral steroid receptor: ancient origin of estrogen signaling. Science. 2003;301(5640):1714–1717. [PubMed] [Google Scholar]
• Torras R, Gonzalez-Crespo S. Posterior expression of nanos orthologs during embryonic and larval development of the anthozoan Nematostella vectensis. The International journal of developmental biology. 2005;49(7):895–899. [PubMed] [Google Scholar]
• Torres JL, Armstrong RA, Corredor JE, Gillbes F. Physiological responses of Acropora cervicornis to increased solar irradiance. Photochemistry and Photobiology. 2007;83(4):839–850. [PubMed] [Google Scholar]
• Twan WH, Hwang JS, Chang CF. Sex steroids in scleractinian coral, Euphyllia ancora: implication in mass spawning. Biology of reproduction. 2003;68(6):2255–2260. [PubMed] [Google Scholar]
• Twan WH, Hwang JS, Lee YH, Wu HF, Tung YH, Chang CF. Hormones and reproduction in scleractinian corals. Comp Biochem Physiol A Mol Integr Physiol. 2006;144(3):247–253. [PubMed] [Google Scholar]
• Uno S, Dalton TP, Shertzer HG, Genter MB, Warshawsky D, Talaska G, et al. Benzo[a]pyrene-induced toxicity: paradoxical protection in Cyp1a1(−/−) knockout mice having increased hepatic BaP-DNA adduct levels. Biochem Biophys Res Commun. 2001;289(5):1049–1056. [PubMed] [Google Scholar]
• Vasiliou V, Nebert DW. Analysis and update of the human aldehyde dehydrogenase (ALDH) gene family. Hum Genomics. 2005;2(2):138–143. [PMC free article] [PubMed] [Google Scholar]
• Vasiliou V, Ross D, Nebert DW. Update of the NAD(P)H:Quinone oxidoreductase (NQO) gene family. Hum Genomics. 2006;2(5):329–335. [PMC free article] [PubMed] [Google Scholar]
• Verde EA, McCloskey LR. A comparative analysis of the photobiology of zooxanthellae and zoochlorellae symbiotic with the temperate clonal anemone Anthopleura elegantissima (Brandt) - II. Effect of light intensity. Marine Biology. 2002;141(2):225–239. [Google Scholar]
• Wellington GM, Fitt WK. Influence of UV radiation on the survival of larvae from broadcast-spawning reef corals. Marine Biology. 2003;143(6):1185–1192. [Google Scholar]
• Whelan S, Goldman N. A general empirical model of protein evolution derived from multiple protein families using a maximum-likelihood approach. Mol Biol Evol. 2001;18(5):691–699. [PubMed] [Google Scholar]
• Wiens M, Ammar MS, Nawar AH, Koziol C, Hassanein HMA, Eisinger M, et al. Induction of heat-shock (stress) protein gene expression by selected natural and anthropogenic disturbances in the octocoral Dendronephthya klunzingeri. Journal of Experimental Marine Biology and Ecology. 2000;245(2):265–276. [PubMed] [Google Scholar]
• Wiger R, Stottum A. In vitro testing for developmental toxicity using the Hydra attenuata assay. NIPH annals. 1985;8(2):43–47. [PubMed] [Google Scholar]
• Winston GW, Mayeaux MH, Heffernan LM. Benzo[a]pyrene metabolism by the intertidal sea anemone, Bunodosoma cavernata. Marine environmental research. 1998;45(1):89–100. [Google Scholar]
• Withers NW, Kokke WC, Fenical W, Djerassi C. Sterol patterns of cultured zooxanthellae isolated from marine invertebrates: Synthesis of gorgosterol and 23-desmethylgorgosterol by aposymbiotic algae. Proc Natl Acad Sci U S A. 1982;79(12):3764–3768. [PMC free article] [PubMed] [Google Scholar]
• Yakovleva I, Bhagooli R, Takemura A, Hidaka M. Differential susceptibility to oxidative stress of two scleractinian corals: antioxidant functioning of mycosporine-glycine. Comp Biochem Physiol B Biochem Mol Biol. 2004;139(4):721–730. [PubMed] [Google Scholar]
• Yamada S, Morimoto H, Fujisawa T, Sugahara K. Glycosaminoglycans in Hydra magnipapillata (Hydrozoa, Cnidaria): demonstration of chondroitin in the developing nematocyst, the sting organelle, and structural characterization of glycosaminoglycans. Glycobiology. 2007;17(8):886–894. [PubMed] [Google Scholar]
• Ziegler DM. An overview of the mechanism, substrate specificities, and structure of FMOs. Drug Metab Rev. 2002;34(3):503–511. [PubMed] [Google Scholar]
• Znidaric D, Liu A, Kalafatic M. Regeneration and Reproduction of Irradiated Green Hydra (Cnidaria) Periodicum Biologorum. 1992;94(2):99–104. [Google Scholar]