Dual Gene Repertoires for Larval and Adult Shells Reveal Molecules Essential for Molluscan Shell Formation.
Dual Gene Repertoires for Larval and Adult Shells Reveal Molecules Essential for Molluscan Shell Formation.
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DOI：
10.1093/molbev/msy172
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发表时间：
2018-11-01
影响因子：
10.7
通讯作者：
Endo K
中科院分区：
文献类型：
--
作者：
Zhao R;Takeuchi T;Luo YJ;Ishikawa A;Kobayashi T;Koyanagi R;Villar-Briones A;Yamada L;Sawada H;Iwanaga S;Nagai K;Satoh N;Endo K
软体动物的贝壳主要由碳酸钙组成，也含有蛋白质和多糖等有机成分。壳有机基质构建了壳结构的框架，并在壳形成过程中调节结晶过程。迄今为止，已经鉴定了许多壳基质蛋白（SMPs），并且已经研究了它们在壳形成中的功能。然而，以前的研究只集中在从成虫壳中提取的SMPs，变态后分泌。利用蛋白质组学分析结合基因组和转录组学分析，我们已经确定了31个SMPs从幼虫贝壳的珍珠，合浦珠母贝，和111从太平洋牡蛎，太平洋牡蛎。幼虫的SMPs几乎完全不同于这两个物种的成年人。RNA-seq数据还证实，幼虫和成虫壳形成的基因表达谱几乎完全不同。因此，双壳类有两个SMP基因库来构建幼虫和成虫的壳。尽管幼虫和成人SMP有相当大的差异，一些功能域共享两个SMP库。保守结构域包括血管性血友病因子A型（VWA）、几丁质结合（CB）、碳酸酐酶（CA）和酸性结构域。这些保守的结构域被认为在壳的形成中起着至关重要的作用。此外，动物基因组的全面调查显示，CA和VWA-CB结构域的蛋白质家族在软体动物从其他Lophotrochozoan linages，如腕足动物分离后扩大。基因扩增后，一些家庭成员被增选为软体动物的SMPs，可能已经触发开发矿化壳从祖先，非矿化几丁质外骨骼。
Molluscan shells, mainly composed of calcium carbonate, also contain organic components such as proteins and polysaccharides. Shell organic matrices construct frameworks of shell structures and regulate crystallization processes during shell formation. To date, a number of shell matrix proteins (SMPs) have been identified, and their functions in shell formation have been studied. However, previous studies focused only on SMPs extracted from adult shells, secreted after metamorphosis. Using proteomic analyses combined with genomic and transcriptomic analyses, we have identified 31 SMPs from larval shells of the pearl oyster, Pinctada fucata, and 111 from the Pacific oyster, Crassostrea gigas. Larval SMPs are almost entirely different from those of adults in both species. RNA-seq data also confirm that gene expression profiles for larval and adult shell formation are nearly completely different. Therefore, bivalves have two repertoires of SMP genes to construct larval and adult shells. Despite considerable differences in larval and adult SMPs, some functional domains are shared by both SMP repertoires. Conserved domains include von Willebrand factor type A (VWA), chitin-binding (CB), carbonic anhydrase (CA), and acidic domains. These conserved domains are thought to play crucial roles in shell formation. Furthermore, a comprehensive survey of animal genomes revealed that the CA and VWA–CB domain-containing protein families expanded in molluscs after their separation from other Lophotrochozoan linages such as the Brachiopoda. After gene expansion, some family members were co-opted for molluscan SMPs that may have triggered to develop mineralized shells from ancestral, nonmineralized chitinous exoskeletons.