Wang Xiudan, Li Changmei, Lv Zhao, Zhang Zhenqiang, Qiu Limei
Shandong Provincial Key Laboratory of Biochemical Engineering, College of Marine Science and Biological Engineering, Qingdao University of Science and Technology, Qingdao 266042, China.
Shandong Provincial Key Laboratory of Biochemical Engineering, College of Marine Science and Biological Engineering, Qingdao University of Science and Technology, Qingdao 266042, China.
Sci Total Environ. 2022 Aug 10;833:155114. doi: 10.1016/j.scitotenv.2022.155114. Epub 2022 Apr 10.
Calcium transportation and homeostasis are essential for marine bivalves to maintain basic metabolism and build their shells. Calmodulin-like proteins (CaLPs) are important calcium sensors and buffers and can respond to ocean acidification (OA) in marine calcifiers. However, no further study of their physiological function in calcium metabolism under elevated CO has been performed. Here, we identified a novel CaLP (designated CgCaLP) in the Pacific oyster Crassostrea gigas and demonstrated its participation in the calcification process: the mRNA expression level of CgCaLP peaked at the trochophore larval stage and remained high at stages when shells were shaped; the mRNA and protein of CgCaLP were more highly expressed in mantle tissue than in other tissues. Under elevated CO levels, the protein expression level of CgCaLP in hemocytes increased, while in contrast, significantly decreased protein levels were detected in gill and mantle tissues. Shell dissolution caused the imbalance of calcium in hemocytes and decreased calcium absorption and transportation demand in gill and mantle tissues, inducing the molecular function allocation of CgCaLP under CO exposure. Despite the decreased protein level in mantle tissue, CgCaLP was found to translocate to outer mantle epithelium (OME) cells where condensed calcium-rich deposits (CRDs) were detected. We further demonstrated that CgCaLP mRNA and protein expression levels could respond to seawater Ca availability, suggesting that the calcium deposition capacity of oysters might be enhanced to fight against shell dissolution problems and that CgCaLP might serve as an essential participator of the process. In summary, CgCaLP might enhance calcium deposition under CO exposure and thus play a significant and flexible molecular function involved in a compensation strategy of oysters to fight against the acidified ocean.
钙的运输和稳态对于海洋双壳贝类维持基本代谢和构建其外壳至关重要。类钙调蛋白（CaLPs）是重要的钙传感器和缓冲剂，并且可以在海洋钙化生物中对海洋酸化（OA）作出反应。然而，尚未对其在升高的二氧化碳浓度下钙代谢中的生理功能进行进一步研究。在此，我们在太平洋牡蛎（Crassostrea gigas）中鉴定出一种新型CaLP（命名为CgCaLP），并证明其参与钙化过程：CgCaLP的mRNA表达水平在担轮幼虫阶段达到峰值，并且在贝壳形成阶段保持较高水平；CgCaLP的mRNA和蛋白在套膜组织中的表达高于其他组织。在升高的二氧化碳水平下，血细胞中CgCaLP的蛋白表达水平增加，而相反，在鳃和套膜组织中检测到蛋白水平显著降低。贝壳溶解导致血细胞中钙的失衡，并降低了鳃和套膜组织中钙的吸收和运输需求，从而诱导了在二氧化碳暴露下CgCaLP的分子功能分配。尽管套膜组织中的蛋白水平降低，但发现CgCaLP易位至外套膜外层上皮（OME）细胞，在那里检测到富含钙的致密沉积物（CRDs）。我们进一步证明，CgCaLP的mRNA和蛋白表达水平可以对海水中钙的可用性作出反应，这表明牡蛎的钙沉积能力可能会增强，以对抗贝壳溶解问题，并且CgCaLP可能是该过程的重要参与者。总之，CgCaLP可能在二氧化碳暴露下增强钙沉积，从而在牡蛎对抗酸化海洋的补偿策略中发挥重要且灵活的分子功能。
