Sainsbury Laboratory, University of Cambridge, Cambridge CB2 1LR, United Kingdom.
Plant Physiol. 2013 Jun;162(2):675-88. doi: 10.1104/pp.113.215277. Epub 2013 Apr 19.
The actin and microtubule cytoskeletons regulate cell shape across phyla, from bacteria to metazoans. In organisms with cell walls, the wall acts as a primary constraint of shape, and generation of specific cell shape depends on cytoskeletal organization for wall deposition and/or cell expansion. In higher plants, cortical microtubules help to organize cell wall construction by positioning the delivery of cellulose synthase (CesA) complexes and guiding their trajectories to orient newly synthesized cellulose microfibrils. The actin cytoskeleton is required for normal distribution of CesAs to the plasma membrane, but more specific roles for actin in cell wall assembly and organization remain largely elusive. We show that the actin cytoskeleton functions to regulate the CesA delivery rate to, and lifetime of CesAs at, the plasma membrane, which affects cellulose production. Furthermore, quantitative image analyses revealed that actin organization affects CesA tracking behavior at the plasma membrane and that small CesA compartments were associated with the actin cytoskeleton. By contrast, localized insertion of CesAs adjacent to cortical microtubules was not affected by the actin organization. Hence, both actin and microtubule cytoskeletons play important roles in regulating CesA trafficking, cellulose deposition, and organization of cell wall biogenesis.
肌动蛋白和微管细胞骨架调节从细菌到后生动物的所有生物门的细胞形状。在具有细胞壁的生物体中，细胞壁是形状的主要限制因素，并且特定细胞形状的产生取决于细胞骨架组织对于细胞壁沉积和/或细胞扩展的作用。在高等植物中，皮层微管通过定位纤维素合酶 (CesA) 复合物的传递并指导其轨迹来定向新合成的纤维素微纤维，从而有助于组织细胞壁的构建。肌动蛋白细胞骨架对于 CesA 向质膜的正常分布是必需的，但是肌动蛋白在细胞壁组装和组织中的更具体作用在很大程度上仍然难以捉摸。我们表明，肌动蛋白细胞骨架的功能是调节 CesA 向质膜的传递速率和 CesA 在质膜上的寿命，这会影响纤维素的产生。此外，定量图像分析表明，肌动蛋白组织会影响 CesA 在质膜上的追踪行为，并且小的 CesA 隔室与肌动蛋白细胞骨架有关。相比之下，邻近皮层微管的 CesA 的局部插入不受肌动蛋白组织的影响。因此，肌动蛋白和微管细胞骨架都在调节 CesA 运输、纤维素沉积和细胞壁生物发生的组织中发挥重要作用。
