Table_4_Transcriptional Responses of Flavin-Containing Monooxygenase Genes in Scallops Exposed to PST-Producing Dinoflagellates Implying Their Involvements in Detoxification.docx

Flavin-containing monooxygenase (FMO) is one of the most prominent xenobiotic metabolic enzymes. It can catalyze the conversion of heteroatom-containing chemicals to polar, readily excretable metabolites and is considered an efficient detoxification system for xenobiotics. Bivalves can accumulate paralytic shellfish toxins (PSTs) produced by dinoflagellates, especially during outbreaks of harmful algal blooms. Exploring FMO genes in bivalves may contribute to a better understanding of the adaptation of these species and the mechanisms of PSTs bioavailability. Therefore, through genome screening, we examined the expansion of FMO genes in two scallops (Patinopecten yessoensis and Chlamys farreri) and found a new subfamily (FMO_like). Our expression analyses revealed that, in both scallops, members of the FMO_N-oxide and FMO_like subfamilies were mainly expressed from the D-stage larvae to juveniles, whereas the FMO_GS-OX subfamily genes were mainly expressed at and prior to the trochophore stage. In adult organs, higher expressions of FMOs were observed in the kidney and hepatopancreas than in other organs. After exposure to PST-producing algae, expression changes in FMOs occurred in hepatopancreas and kidney of both scallops, with more members being up-regulated in hepatopancreas than in kidney for Alexandrium catenella exposure, while more up-regulated FMOs were found in kidney than in hepatopancreas of C. farreri exposed to A. minutum. Our findings suggest the adaptive functional diversity of scallop FMO genes in coping with the toxicity of PST-producing algae.

黄素蛋白单加氧酶（FMO）乃异生物代谢酶类中最为显著的成员之一。此酶能催化含有杂原子的化学物质转化为极性、易于排泄的代谢产物，被视为异生物的有效解毒系统。双壳类生物能够累积由甲藻产生的麻痹性贝类毒素（PSTs），尤其是在有害藻华爆发期间。探究双壳类生物中的FMO基因，有助于深化对这些物种适应性及PSTs生物利用度机制的认知。因此，通过基因组筛选，我们检视了两类扇贝（长牡蛎 Patinopecten yessoensis 和江珧 Chlamys farreri）中FMO基因的扩张，并发现一个新的亚家族（FMO_like）。我们的表达分析揭示，在两种扇贝中，FMO_N-oxide和FMO_like亚家族的成员主要在D阶段幼虫至幼贝阶段表达，而FMO_GS-OX亚家族基因主要在担轮幼虫阶段及其之前表达。在成体器官中，FMOs在肾脏和肝胰腺中的表达高于其他器官。在接触产生PST的藻类之后，两种扇贝的肝胰腺和肾脏中FMOs的表达发生了变化，对于亚历山大链藻（Alexandrium catenella）的暴露，肝胰腺中上调的FMO成员数量多于肾脏；而对于江珧在微链藻（A. minutum）暴露下，肾脏中上调的FMO数量则多于肝胰腺。我们的研究结果表明，扇贝FMO基因在应对产生PST的藻类毒性中表现出适应性功能多样性。