A Novel Cyclophilin B Gene in the Red Tide DinoflagellateCochlodinium polykrikoides: Molecular Characterizations and Transcriptional Responses to Environmental Stresses

Abstract

The marine dinoflagellateCochlodinium polykrikoidesis one of the most common ichthyotoxic species that causes harmful algal blooms (HABs), which leads to ecological damage and huge economic loss in aquaculture industries. Cyclophilins (CYPs) belong to the immunophilin superfamily, and they may play a role in the survival mechanisms of the dinoflagellate in stress environments. In the present study, we identified a novel cyclophilin gene fromC. polykrikoidesand examined physiological and gene transcriptional responses to biocides copper sulphate (CuSO4) and sodium hypochlorite (NaOCl). The full length ofCpCYPwas 903 bp, ranging from the dinoflagellate splice leader (DinoSL) sequence to the polyA tail, comprising a 639 bp ORF, a 117 bp 5′-UTR, and a 147 bp 3′-UTR. Motif and phylogenetic comparisons showed that CpCYP was affiliated to group B of CYP. In biocide stressors, cell counts, chlorophylla, and photosynthetic efficiency (Fv/Fm) ofC. polykrikoideswere considerably decreased in both exposure time- and dose-dependent manners. In addition,CpCYPgene expression was significantly induced after 24 h exposure to the biocide-treated stress conditions. These results indicate an effect of the biocides on the cell physiology and expression profile ofCpCYP, suggesting that the gene may play a role in environmental stress responses.