Some species of the genus Pseudo-nitzschia produce the toxin
domoic acid, which causes
amnesic shellfish poisoning (ASP). Given that bivalve mollusks are filter feeders, they can accumulate these toxins in their tissues. To elucidate the transcriptional response of the queen scallop Aequipecten opercularis after exposure to
domoic acid-producing Pseudo-nitzschia, the digestive gland transcriptome was de novo assembled using an Illumina HiSeq 2000 platform. Then, a differential gene expression analysis was performed. After the assembly, 142,137 unigenes were obtained, and a total of 10,144 genes were differentially expressed in the groups exposed to the toxin. Functional enrichment analysis found that 374 Pfam (
protein families database) domains were significantly enriched. The C1q domain, the
C-type lectin, the major facilitator superfamily, the immunoglobulin domain, and the
cytochrome P450 were among the most enriched Pfam domains.
Protein network analysis showed a small number of highly connected nodes involved in specific functions:
proteasome components, mitochondrial
ribosomal proteins,
protein translocases of mitochondrial membranes,
cytochromes P450, and
glutathione S-
transferases. The results suggest that exposure to
domoic acid-producing organisms causes oxidative stress and
mitochondrial dysfunction. The transcriptional response counteracts these effects with the up-regulation of genes coding for some
mitochondrial proteins,
proteasome components, and
antioxidant enzymes (
glutathione S-
transferases,
thioredoxins,
glutaredoxins, and
copper/
zinc superoxide dismutases).