Genomics Study of the Exposure Effect of Gymnodinium catenatum, a Paralyzing Toxin Producer, on Crassostrea gigas' Defense System and Detoxification Genes

Abstract

Background Crassostrea gigas accumulates paralytic shellfish toxins (PST) associated with red tide species as Gymnodinium catenatum. Previous studies demonstrated bivalves show variable feeding responses to toxic algae at physiological level; recently, only one study has reported biochemical changes in the transcript level of the genes involved in C. gigas stress response.Principal FindingsWe found that 24 h feeding on toxic dinoflagellate cells (acute exposure) induced a significant decrease in clearance rate and expression level changes of the genes involved in antioxidant defense (copper/zinc superoxide dismutase, Cu/Zn-SOD), cell detoxification (glutathione S-transferase, GST and cytochrome P450, CPY450), intermediate immune response activation (lipopolysaccharide and beta glucan binding protein, LGBP), and stress responses (glutamine synthetase, GS) in Pacific oysters compared to the effects with the non-toxic microalga Isochrysis galbana. A sub-chronic exposure feeding on toxic dinoflagellate cells for seven and fourteen days (30×103 cells mL−1) showed higher gene expression levels. A significant increase was observed in Cu/Zn-SOD, GST, and LGBP at day 7 and a major increase in GS and CPY450 at day 14. We also observed that oysters fed only with G. catenatum (3×103 cells mL−1) produced a significant increase on the transcription level than in a mixed diet (3×103 cells mL−1 of G. catenatum+0.75×106 cells mL−1 I. galbana) in all the analyzed genes.ConclusionsOur results provide gene expression data of PST producer dinoflagellate G. catenatum toxic effects on C. gigas, a commercially important bivalve. Over expressed genes indicate the activation of a potent protective mechanism, whose response depends on both cell concentration and exposure time against these toxic microalgae. Given the importance of dinoflagellate blooms in coastal environments, these results provide a more comprehensive overview of how oysters respond to stress generated by toxic dinoflagellate exposure.

Exposure to toxic Alexandrium minutum activates the detoxifying and antioxidant systems in gills of the oyster Crassostrea gigas

“…For example, increases in GST activity was observed in the digestive gland of the mussel Mytilus edulis after intra-muscular injection of STX, and in the liver of the salmon Salmo salar following injection with STX or extract of toxic dinoflagellates (Gubbins et al, , 2001. Increased mRNA levels of GST were observed in juvenile oysters exposed to the PST-producer Gymnodinium catenatum (García-Lagunas et al, 2013). Conversely, in the clam, Ruditapes philippinarum, exposed to Alexandrium tamarense, a negative correlation was observed between PST concentration and GST activity in gills (Choi et al, 2006).…”

Differential expression of immune response genes in Pacific oyster, Crassostrea gigas spat, fed with dinoflagellates Gymnodinium catenatum and Prorocentrum lima

“…Paralytic shellfish toxins (PSTs) are a group of neurotoxic alkaloids, grouped into three structural families: carbamate (saxitoxin-STX, neosaxitoxin-NEO and gonyautoxins-GTX1 to GTX4), decarbamoyl and N-sulfocarbamoyl (Oshima, 1995). These dinoflagellate species have been associated with DSP and PSP episodes in different parts of the world, and in the Gulf of California, they have also been extensively used in aquatic toxicological studies (Pinto-Silva et al, 2005;Wikfors, 2005;Flórez-Barrós et al, 2011;García-Lagunas et al, 2013Romero-Geraldo et al, 2014, 2016.…”

“…Molecular studies with both toxins cause differential expression level on the genes involved in immune (García-Lagunas et al, 2013;Mello et al, 2013;Lassundrie et al, 2014Lassundrie et al, , 2015a. In other hand, proteins of immune system (as carvotin, Interaction protein-Toll, immunoglobulin and Protein 44 interferoninduced) on oyster spats had a detectable and differentiated concentration in response to the low (3×10 2 cell mL -1 ) and high concentrations (3×10 3 cell mL -1 ) of P. lima (M.A.…”

“…Gymnodinium catenatum was reared as described in García-Lagunas et al (2013). P. lima and Isochrysis galbana were grown as described in Romero-Geraldo et al (2014).…”

Mortality and ostreid herpesvirus 1 infection in the pacific oyster Crassostrea gigas in the Gulf of La Spezia, Italy

“…The environmental parameters (data not shown) showed a stability of the Gulf and are consistent with the seasonal variations, and the statistical analysis did not reveal a positive correlation with either the presence of the virus and Vibrio or mortality. Likewise, also the measurement of toxic algae has not revealed any data that showed positive correlation, although in some studies, it has been hypothesized that the accumulation of toxins inside oysters could interfere with the immune system (García-Lagunas et al 2013). …”