Data_Sheet_1_Mantle Modularity Underlies the Plasticity of the Molluscan Shell: Supporting Data From Cepaea nemoralis.xlsx

Molluscs have evolved the capacity to fabricate a wide variety of shells over their 540+ million-year history. While modern sequencing and proteomic technologies continue to expand the catalog of molluscan shell-forming proteins, a complete functional understanding of how any mollusc constructs its shell remains an ambitious goal. This lack of understanding also constrains our understanding of how evolution has generated a plethora of molluscan shell morphologies. Taking advantage of a previous expression atlas for shell-forming genes in Lymnaea stagnalis, I have characterized the spatial expression patterns of seven shell-forming genes in the terrestrial gastropod Cepaea nemoralis, with the aim of comparing and contrasting their expression patterns between the two species. Four of these genes were selected from a previous proteomic screen of the C. nemoralis shell, two were targeted by bioinformatics criteria designed to identify likely shell-forming gene products, and the final one was a clear homolog of a peroxidase sequence in the L. stagnalis dataset. While the spatial expression patterns of all seven C. nemoralis genes could be recognized as falling into distinct zones within the mantle tissue similar to those established in L. stagnalis, some zones have apparently been modified. These similarities and differences hint at a modularity to the molluscan mantle that may provide a mechanistic explanation as to how evolution has efficiently generated a diversity of molluscan shells.

在长达5.4亿多年的演化历程中，软体动物（Molluscs）演化出了合成多种贝壳的能力。尽管现代测序技术与蛋白质组学技术持续扩充软体动物贝壳形成蛋白（shell-forming proteins）的收录名录，但目前我们仍未能完全阐明任意一种软体动物构建贝壳的完整机制，这仍是一项颇具挑战性的目标。这种认知缺失也制约了我们对演化如何产生如此多样的软体动物贝壳形态的理解。本研究借助此前针对静水椎实螺（Lymnaea stagnalis）贝壳形成基因构建的表达图谱（expression atlas），对陆生腹足类动物花园葱蜗牛（Cepaea nemoralis）的7个贝壳形成基因的空间表达谱进行了解析，旨在对比这两个物种间的基因表达模式差异。其中4个基因源自此前针对花园葱蜗牛贝壳开展的蛋白质组筛选结果，2个基因通过用于筛选潜在贝壳形成基因产物的生物信息学标准选定，最后1个则是静水椎实螺数据集里明确的过氧化物酶（peroxidase）序列同源基因。尽管花园葱蜗牛这7个基因的空间表达谱均可归类于外套膜组织（mantle tissue）内的特定区域，且这些区域与静水椎实螺中已确认的区域具有相似性，但部分区域显然已发生演化修饰。这些相似性与差异暗示了软体动物外套膜存在模块化特征，这或许能为演化如何高效造就多样的软体动物贝壳提供机制层面的解释。