Pif is an acid matrix protein that is known to be a key macromolecule in the shell nacre formation of molluscs. However, the investigation into the Pif gene at the whole genome level has seldom been carried out, limiting the systematic understanding of its evolution and function. The Yesso scallop (Patinopecten yessoensis), an ancient bivalve with important economic value and evolutionary status, has suffered severe shell infestation by Polydora that badly damaged shell structures. In this study, a total of eight Pif homologous genes (PyPif1–7 and PyBMSP) were identified in the whole genome of the Yesso scallop with diverse gene structures. Two conserved functional domains, VWA and chitin-binding domains, were detected in all PyPif proteins, although with variation in number of copies. Phylogenetic analysis of the Pifs among different molluscan species suggested the molecular evolution of Pif genes was consistent with taxonomic relationships. High sequence divergence of Pif proteins existed among the different species, but a high level of similarity was found in BMSPs, which own four VWA domains. High expression levels of PyBMSP in the central mantles of the healthy and Polydora shell infested Yesso scallops indicated its important role in shell formation. The other PyPifs (PyPif2, PyPif3, PyPif4, PyPif5, PyPif6) may function when the shell is injured, as significantly increased expression levels of these genes were found in the edge mantles of the infested scallops. In addition, haemocytes may also participate in shell repair by up-regulating the expression of PyPifs. This study provides new insights into the evolution and expression patterns of Pif genes in molluscs, which are valuable for elucidating the mechanism of shell repair and formation.

Pif 是一种酸性基质蛋白，已知它是软体动物壳珍珠层形成中的关键大分子。然而，在全基因组水平上对Pif基因的研究很少进行，限制了对其进化和功能的系统理解。Yesso扇贝（Patinopecten yessoensis）是一种具有重要经济价值和进化地位的古老双壳类动物，受到Polydora的严重贝壳侵扰，严重破坏了贝壳结构。在这项研究中，共八个PIF同源基因（PyPif1 - 7和PyBMSP) 在具有不同基因结构的 Yesso 扇贝的整个基因组中被鉴定出来。在所有 PyPif 蛋白中检测到两个保守的功能域，VWA 和几丁质结合域，尽管拷贝数有所不同。不同软体动物物种之间Pif 的系统发育分析表明Pif基因的分子进化与分类关系一致。Pif 蛋白在不同物种之间存在高度序列差异，但在 BMSP 中发现了高度相似性，BMSP 拥有四个 VWA 结构域。PyBMSP在健康和Polydora贝壳出没的 Yesso 扇贝的中央地幔中的高表达水平表明其在贝壳形成中的重要作用。其他PyPifs (PyPif2、PyPif3、PyPif4、PyPif5、PyPif6）可能在贝壳受损时起作用，因为在受感染扇贝的边缘地幔中发现这些基因的表达水平显着增加。此外，血细胞也可能通过上调PyPifs的表达参与壳修复。这项研究为软体动物Pif基因的进化和表达模式提供了新的见解，这对于阐明壳修复和形成的机制很有价值。