Department of Plant Sciences, University of Oxford, Oxford, United Kingdom.
Department of Engineering Science, University of Oxford, Oxford, United Kingdom.
Elife. 2019 Jul 29;8:e47988. doi: 10.7554/eLife.47988.
Morphogenesis in plants depends critically on directional (anisotropic) growth. This occurs principally perpendicular to the net orientation of cellulose microfibrils (CMFs), which is in turn controlled by cortical microtubules (CMTs). In young lateral roots of , growth anisotropy also depends on RAB-A5c, a plant-specific small GTPase that specifies a membrane trafficking pathway to the geometric edges of cells. Here we investigate the functional relationship between structural anisotropy at faces and RAB-A5c activity at edges during lateral root development. We show that surprisingly, inhibition of RAB-A5c function is associated with increased CMT/CMF anisotropy. We present genetic, pharmacological, and modelling evidence that this increase in CMT/CMF anisotropy partially compensates for loss of an independent RAB-A5c-mediated mechanism that maintains anisotropic growth in meristematic cells. We show that RAB-A5c associates with CMTs at cell edges, indicating that CMTs act as an integration point for both mechanisms controlling cellular growth anisotropy in lateral roots.
植物的形态发生取决于方向（各向异性）的生长。这种生长主要发生在与纤维素微纤丝（CMFs）的净取向垂直的位置，而纤维素微纤丝的取向又受皮层微管（CMTs）的控制。在拟南芥的幼侧根中，生长的各向异性也依赖于 RAB-A5c，这是一种植物特异性的小 GTPase，它指定了一个膜运输途径，将物质运送到细胞的几何边缘。在这里，我们研究了侧向根发育过程中面的结构各向异性和边缘处 RAB-A5c 活性之间的功能关系。我们惊讶地发现，抑制 RAB-A5c 的功能与 CMT/CMF 各向异性的增加有关。我们提供了遗传、药理学和建模证据，表明 CMT/CMF 各向异性的增加部分补偿了独立的 RAB-A5c 介导的机制的丧失，该机制维持了分生细胞中各向异性的生长。我们发现 RAB-A5c 与细胞边缘的 CMTs 相关联，这表明 CMTs 是控制侧根中细胞生长各向异性的两种机制的整合点。
