Department of Plant Biology and Forest Genetics, Uppsala BioCenter, Swedish University of Agricultural Sciences and Linean Center for Plant Biology, SE-75007 Uppsala, Sweden.
Plant Cell. 2013 Jun;25(6):2171-86. doi: 10.1105/tpc.113.113043. Epub 2013 Jun 28.
Vesicle trafficking plays an important role in cell division, establishment of cell polarity, and translation of environmental cues to developmental responses. However, the molecular mechanisms regulating vesicle trafficking remain poorly understood. Here, we report that the evolutionarily conserved caspase-related protease separase (extra spindle poles [ESP]) is required for the establishment of cell polarity and cytokinesis in Arabidopsis thaliana. At the cellular level, separase colocalizes with microtubules and RabA2a (for RAS genes from rat brainA2a) GTPase-positive structures. Separase facilitates polar targeting of the auxin efflux carrier PIN-formed2 (PIN2) to the rootward side of the root cortex cells. Plants with the radially swollen4 (rsw4) allele with compromised separase activity, in addition to mitotic failure, display isotropic cell growth, perturbation of auxin gradient formation, slower gravitropic response in roots, and cytokinetic failure. Measurements of the dynamics of vesicle markers on the cell plate revealed an overall reduction of the delivery rates of KNOLLE and RabA2a GTPase in separase-deficient roots. Furthermore, dissociation of the clathrin light chain, a protein that plays major role in the formation of coated vesicles, was slower in rsw4 than in the control. Our results demonstrate that separase is a key regulator of vesicle trafficking, which is indispensable for cytokinesis and the establishment of cell polarity.
囊泡运输在细胞分裂、细胞极性的建立以及环境信号向发育反应的转化中起着重要作用。然而，调节囊泡运输的分子机制仍知之甚少。在这里，我们报告称，进化上保守的半胱天冬酶相关蛋白酶分离酶（额外纺锤极体 [ESP]）是拟南芥细胞极性和胞质分裂建立所必需的。在细胞水平上，分离酶与微管和 RabA2a（大鼠脑 A2a 的 RAS 基因）GTPase 阳性结构共定位。分离酶有助于生长素外排载体 PIN-formed2（PIN2）向根皮层细胞的根向侧的极性靶向。除有丝分裂失败外，具有削弱分离酶活性的径向肿胀 4（rsw4）等位基因的植物还表现出各向同性细胞生长、生长素梯度形成受到干扰、根的向地性反应较慢以及胞质分裂失败。对细胞板上囊泡标记物的动力学测量显示，分离酶缺陷根中 KNOLLE 和 RabA2a GTPase 的递送率总体降低。此外，clathrin 轻链的解离（在形成有被小泡中起主要作用的蛋白质）在 rsw4 中比在对照中更慢。我们的结果表明，分离酶是囊泡运输的关键调节剂，对于胞质分裂和细胞极性的建立是必不可少的。
