Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, Massachusetts 01609, USA.
Bioengineering Department, Temple University, Philadelphia, Pennsylvania 19122, USA.
Plant Physiol. 2021 Dec 4;187(4):2509-2529. doi: 10.1093/plphys/kiab435.
In tip-growing plant cells, growth results from myosin XI and F-actin-mediated deposition of cell wall polysaccharides contained in secretory vesicles. Previous evidence showed that myosin XI anticipates F-actin accumulation at the cell's tip, suggesting a mechanism where vesicle clustering via myosin XI increases F-actin polymerization. To evaluate this model, we used a conditional loss-of-function strategy by generating moss (Physcomitrium patens) plants harboring a myosin XI temperature-sensitive allele. We found that loss of myosin XI function alters tip cell morphology, vacuolar homeostasis, and cell viability but not following F-actin depolymerization. Importantly, our conditional loss-of-function analysis shows that myosin XI focuses and directs vesicles at the tip of the cell, which induces formin-dependent F-actin polymerization, increasing F-actin's local concentration. Our findings support the role of myosin XI in vesicle focusing, possibly via clustering and F-actin organization, necessary for tip growth, and deepen our understanding of additional myosin XI functions.
在顶端生长的植物细胞中，生长是由肌球蛋白 XI 和肌动蛋白介导的，包含在分泌小泡中的细胞壁多糖的沉积。先前的证据表明，肌球蛋白 XI 预测 F-肌动蛋白在细胞尖端的积累，这表明一种通过肌球蛋白 XI 聚集囊泡来增加 F-肌动蛋白聚合的机制。为了评估该模型，我们通过生成含有肌球蛋白 XI 温度敏感等位基因的藓类（Physcomitrium patens）植物来使用条件性功能丧失策略。我们发现，肌球蛋白 XI 功能的丧失会改变顶端细胞的形态、液泡动态平衡和细胞活力，但不会导致 F-肌动蛋白解聚。重要的是，我们的条件性功能丧失分析表明，肌球蛋白 XI 将囊泡集中在细胞的尖端，这诱导了formin 依赖性的 F-肌动蛋白聚合，增加了 F-肌动蛋白的局部浓度。我们的发现支持肌球蛋白 XI 在囊泡聚焦中的作用，可能通过聚集和 F-肌动蛋白组织，这是顶端生长所必需的，并加深了我们对肌球蛋白 XI 其他功能的理解。
