Table1_Characterization and evolutionary diversification of the phospholipase D gene family in mosses.XLSX

Plant phospholipase D (PLD) exerts important roles in various biological processes, such as intracellular signaling and morphological development. Our knowledge about early land plant PLDs is still underdeveloped. In this study, we identified 84 PLD genes in six mosses, i.e., Physcomitrella patens, Ceratodon purpureus, Fontinalis antipyretica, Pleurozium schreberi, Sphagnum magellanicum, and Sphagnum fallax. These PLDs were classified into four clades (I–IV). We showed that PLD underwent rapid expansion in mosses. A total of six conserved domains and two core HKD motifs were detected. Structure analysis uncovered that the moss PLDs from within a clade generally exhibited similar exon-intron organization. Cis-elements prediction and expression analyses indicated that P. patens PLDs had key roles in stress responsiveness and plant development. Particularly, about half of the P. patens PLDs (e.g., PpPLD1, PpPLD2, and PpPLD5) were differentially expressed under biotic and abiotic stresses. We also determined the expression pattern of P. patens PLD genes in various tissues and at different stages of development. Although the moss, clubmoss, liverwort, and fern PLDs evolved largely under functional constraints, we found episodic positive selection in the moss PLDs, e.g., C. purpureus PLD2 and P. patens PLD11. We infer that the evolutionary force acting on the PLDs may have facilitated moss colonization of land. Our work provides valuable insights into the diversification of moss PLD genes, and can be used for future studies of their functions.

植物磷脂酶D（phospholipase D, PLD）在细胞内信号转导、形态发育等多种生物学过程中发挥重要作用。目前学界对早期陆生植物PLD的认知仍有待深化。本研究从6种苔藓——小立碗藓（Physcomitrella patens）、紫萼藓（Ceratodon purpureus）、水藓（Fontinalis antipyretica）、塔藓（Pleurozium schreberi）、大泥炭藓（Sphagnum magellanicum）及细叶泥炭藓（Sphagnum fallax）——中共鉴定得到84个PLD基因。这些PLD可被划分为4个进化枝（clade）I~IV。分析表明，苔藓PLD家族经历了快速扩张事件。本研究共检测到6个保守结构域与2个核心HKD基序（HKD motif）。结构解析显示，同一进化枝内的苔藓PLD通常具有相似的外显子-内含子结构（exon-intron organization）。顺式作用元件（cis-element）预测与表达谱分析结果表明，小立碗藓PLD在胁迫响应及植株发育过程中扮演关键角色。尤为值得关注的是，约半数小立碗藓PLD基因（如PpPLD1、PpPLD2与PpPLD5）在生物胁迫与非生物胁迫条件下呈现差异表达模式。本研究还明确了小立碗藓PLD基因在不同组织及不同发育阶段的表达模式。尽管苔藓、石松、地钱与蕨类的PLD在进化过程中主要受功能约束，但研究发现苔藓PLD家族存在间歇性正选择现象，例如紫萼藓PLD2与小立碗藓PLD11。本研究推测，作用于PLD家族的进化动力可能推动了苔藓的陆地定植过程。本研究为苔藓PLD基因的功能分化提供了宝贵见解，可为后续PLD基因的功能研究提供重要参考。