Symbiotic rhizobium–legume interactions, such as root hair curling, rhizobial invasion, infection thread expansion, cell division and proliferation of nitrogen‐fixing bacteroids, and nodule formation, involve extensive membrane synthesis, lipid remodeling and cytoskeleton dynamics. However, little is known about these membrane–cytoskeleton interfaces and related genes. Here, we report the roles of a major root phospholipase D (PLD), PLDα1, and its enzymatic product, phosphatidic acid (PA), in rhizobium–root interaction and nodulation. PLDα1 was activated and the PA content transiently increased in roots after rhizobial infection. Levels of PLDα1 transcript and PA, as well as actin and tubulin cytoskeleton‐related gene expression, changed markedly during root–rhizobium interactions and nodule development. Pre‐treatment of the roots of soybean seedlings with n‐butanol suppressed the generation of PLD‐derived PA, the expression of early nodulation genes and nodule numbers. Overexpression or knockdown of GmPLDα1 resulted in changes in PA levels, glycerolipid profiles, nodule numbers, actin cytoskeleton dynamics, early nodulation gene expression and hormone levels upon rhizobial infection compared with GUS roots. The transcript levels of cytoskeleton‐related genes, such as GmACTIN, GmTUBULIN, actin capping protein 1 (GmCP1) and microtubule‐associating protein (GmMAP1), were modified in GmPLDα1‐altered hairy roots compared with those of GUS roots. Phosphatidic acid physically bound to GmCP1 and GmMAP1, which could be related to cytoskeletal changes in rhizobium‐infected GmPLDα1 mutant roots. These data suggest that PLDα1 and PA play important roles in soybean–rhizobium interaction and nodulation. The possible underlying mechanisms, including PLDα1‐ and PA‐mediated lipid signaling, membrane remodeling, cytoskeleton dynamics and related hormone signaling, are discussed herein.

中文翻译：

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磷脂酶 D 和磷脂酸介导的磷脂代谢和信号调节大豆中的共生相互作用和结瘤（Glycine max）

共生根瘤菌-豆科植物的相互作用，例如根毛卷曲、根瘤菌入侵、感染线扩张、细胞分裂和固氮类菌体增殖以及根瘤形成，涉及广泛的膜合成、脂质重塑和细胞骨架动力学。然而，对这些膜-细胞骨架界面和相关基因知之甚少。在这里，我们报告了主要根磷脂酶 D (PLD)、PLDα1 及其酶产物磷脂酸 (PA) 在根瘤菌-根相互作用和结瘤中的作用。根瘤菌侵染后，PLDα1被激活，根中PA含量瞬时升高。PLDα1的水平转录本和 PA 以及肌动蛋白和微管蛋白细胞骨架相关基因的表达，在根 - 根瘤菌相互作用和根瘤发育过程中发生显着变化。用正丁醇预处理大豆幼苗根部可抑制 PLD 衍生 PA 的产生、早期根瘤基因的表达和根瘤数。与 GUS 根相比，GmPLDα1 的过表达或敲低导致 PA 水平、甘油脂谱、根瘤数量、肌动蛋白细胞骨架动力学、根瘤菌感染后的早期根瘤基因表达和激素水平发生变化。细胞骨架相关基因的转录水平，如GmACTIN、GmTUBULIN、肌动蛋白加帽蛋白 1（GmCP1) 和微管相关蛋白 ( GmMAP1 )，与 GUS 根相比，在GmPLDα1改变的毛状根中进行了修饰。磷脂酸与 GmCP1 和 GmMAP1 物理结合，这可能与根瘤菌感染的GmPLDα1突变体根的细胞骨架变化有关。这些数据表明 PLDα1 和 PA 在大豆-根瘤菌相互作用和结瘤中起重要作用。本文讨论了可能的潜在机制，包括 PLDα1 和 PA 介导的脂质信号传导、膜重塑、细胞骨架动力学和相关激素信号传导。