AUTHOR=Xin Xiaoyu , Liu Chang , Liu Zhaoqun , Zhang Yukun , Gao Yuqian , Zhu Ting , Wang Lingling , Song Linsheng 

TITLE=Calmodulin regulates the calcium homeostasis in mantle of Crassostrea gigas under ocean acidification

JOURNAL=Frontiers in Marine Science

VOLUME=9

YEAR=2022

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2022.1050022

DOI=10.3389/fmars.2022.1050022

ISSN=2296-7745

ABSTRACT=<p>The biosynthesis of shell is a complicated calcification process in the marine bivalve, which can be severely impacted by ocean acidification (OA). Calmodulin (CaM) is a pivotal calcium regulator and thought to be crucial for calcification. In the present study, a CaM (designated <italic>Cg</italic>CaM) with calcium-binding activity was identified from the Pacific oyster <italic>Crassostrea gigas</italic> with the objective to understand its possible role in the regulation of calcium homeostasis under acidification treatment. The open reading frame (ORF) of <italic>Cg</italic>CaM was of 474 bp encoding a 17.5 kDa protein with four continuous EF-hand domains. <italic>Cg</italic>CaM shared high similarity with CaMs from other invertebrates and vertebrates. The mRNA transcript of <italic>Cg</italic>CaM was constitutively expressed in all detected tissues with the higher expression level in mantle, especially highest in the middle fold of the three folds of mantle. <italic>Cg</italic>CaM was found to be mainly distributed in the mantle epithelium. When the oysters were exposed to acidified seawater, the expression level of <italic>Cg</italic>CaM in the middle fold of mantle and the content of Ca<sup>2+</sup> in this fold both decreased significantly. These results collectively suggested that <italic>Cg</italic>CaM was involved in the regulation of calcium homeostasis in the middle fold of mantle under acidification treatment.</p>