Seawater carbonate chemistry and larval viability, size, development, and shell mineralization of the eastern oyster (Crassostrea virginica)

Calcifying marine organisms, including the eastern oyster (Crassostrea virginica), are vulnerable to ocean acidification (OA) because it is more difficult to precipitate calcium carbonate (CaCO3). Previous investigations of the molecular mechanisms associated with resilience to OA in C. virginica demonstrated significant differences in single nucleotide polymorphism and gene expression profiles among oysters reared under ambient and OA conditions. Converged evidence generated by both of these approaches highlighted the role of genes related to biomineralization, including perlucins. Here, gene silencing via RNA interference (RNAi) was used to evaluate the protective role of a perlucin gene under OA stress. Larvae were exposed to short dicer-substrate small interfering RNA (DsiRNA-perlucin) to silence the target gene or to one of two control treatments (control DsiRNA or seawater) before cultivation under OA (pH ~7.3) or ambient (pH ~8.2) conditions. Two transfection experiments were performed in parallel, one during fertilization and one during early larval development (6 h post-fertilization), before larval viability, size, development, and shell mineralization were monitored. Silenced oysters under acidification stress were the smallest, had shell abnormalities, and had significantly reduced shell mineralization, thereby suggesting that perlucin significantly helps larvae mitigate the effects of OA.

钙化海洋生物（包括东部牡蛎Crassostrea virginica）易受海洋酸化（OA）影响，因为碳酸钙（CaCO3）的沉淀难度增加。此前针对C. virginica对OA耐受性相关分子机制的研究表明，在环境条件和OA条件下饲养的牡蛎之间，单核苷酸多态性（single nucleotide polymorphism）和基因表达谱存在显著差异。这两种方法产生的综合证据凸显了与生物矿化（biomineralization）相关基因的作用，包括珍珠层蛋白（perlucin）基因。本研究采用RNA干扰（RNAi）介导的基因沉默技术，评估perlucin基因在OA胁迫下的保护作用。幼虫在OA（pH~7.3）或环境条件（pH~8.2）下培养前，分别暴露于靶向沉默该基因的短切丁酶底物小干扰RNA（DsiRNA-perlucin），或两种对照处理之一（对照DsiRNA或海水）。同时进行了两项转染实验：一项在受精期间，另一项在早期幼虫发育阶段（受精后6小时），随后监测幼虫存活率、大小、发育情况及贝壳矿化程度。酸化胁迫下的沉默组牡蛎体型最小，存在贝壳畸形，且贝壳矿化程度显著降低，这表明perlucin能显著帮助幼虫缓解OA的影响。