Min Yue, Li Qi, Yu Hong
Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, and College of Fisheries, Ocean University of China, Qingdao 266003, China.
Key Laboratory of Mariculture (Ocean University of China), Ministry of Education, and College of Fisheries, Ocean University of China, Qingdao 266003, China; Laboratory for Marine Fisheries Science and Food Production Processes, Qingdao National Laboratory for Marine Science and Technology, Qingdao 266237, China.
Comp Biochem Physiol B Biochem Mol Biol. 2023 Jan;263:110783. doi: 10.1016/j.cbpb.2022.110783. Epub 2022 Aug 1.
Shell formation is a dynamic process involving organic matrix secretion and calcification. In this study, we characterized shell morphogenesis during larval development in Crassostrea gigas. Using scanning electron microscopy (SEM) and fluorescence staining, we demonstrated that shell field, the first morphologically distinguishable shell-forming tissue, became visible soon after enlargement of the blastopore at the anterior end of the trochophore. Shell organic matrix namely protein polysaccharides and calcified structure appeared as a slit at the dorsal side of the embryo. The early shell field began to extend along the dorsal side of the trochophore larvae, and became a saddle shaped shell field that gave rise to the prodissoconch I embryonic shell in the early D-shaped larvae. Subsequently, prodissoconch II shell was formed in the late D-shaped larvae with a characteristic appearance of growth lines. To identify gene expression markers for studying shell formation, we isolated three potential larval shell formation genes CgPOU2F1, CgSox5, and CgPax6 and analyzed their expression during shell morphogenesis. The three potential shell formation genes possessed a similar pattern of expression. Their expression was detected in the shell gland and shell field regions in early D-shaped larvae, hereafter, their expression was detected at the larval mantle edge in the calcified shell stages. Together, these studies provide knowledge of shell morphogenesis in pacific oyster and molecular markers for studying the molecular regulation of biomineralization and shell formation.
贝壳形成是一个涉及有机基质分泌和钙化的动态过程。在本研究中，我们对太平洋牡蛎幼虫发育过程中的贝壳形态发生进行了表征。利用扫描电子显微镜（SEM）和荧光染色，我们证明了贝壳场，即第一个在形态上可区分的贝壳形成组织，在担轮幼虫前端的胚孔扩大后不久就可见了。贝壳有机基质，即蛋白多糖和钙化结构，在胚胎的背侧呈现为一条裂缝。早期的贝壳场开始沿着担轮幼虫的背侧延伸，并变成一个鞍形的贝壳场，在早期D形幼虫中形成原壳I胚胎贝壳。随后，在晚期D形幼虫中形成原壳II贝壳，具有特征性的生长线外观。为了鉴定用于研究贝壳形成的基因表达标记，我们分离了三个潜在的幼虫贝壳形成基因CgPOU2F1、CgSox5和CgPax6，并分析了它们在贝壳形态发生过程中的表达。这三个潜在的贝壳形成基因具有相似的表达模式。在早期D形幼虫的贝壳腺和贝壳场区域检测到它们的表达，此后，在钙化贝壳阶段的幼虫外套膜边缘检测到它们的表达。总之，这些研究提供了太平洋牡蛎贝壳形态发生的知识以及用于研究生物矿化和贝壳形成分子调控的分子标记。
