Department of Biology, McGill University, 1205 Dr Penfield Avenue, Montreal, Quebec H3A 1B1, Canada.
Mol Plant. 2013 May;6(3):847-59. doi: 10.1093/mp/sss116. Epub 2012 Oct 16.
In plant cells, Rab-A proteins have been implicated to play important roles in membrane trafficking from the trans-Golgi network (TGN) to the plasma membrane/cell wall and to the newly formed cell plate in cytokinesis. But how different Rab-A proteins may work in the TGN is not well studied. We show here that RAB-A1c defines a population of TGN that is partially overlapped with the VHA-a1 marked-TGN. Interestingly, the morphology of RAB-A1c defined-TGN is sensitive to endosidin 1 (ES1), but not to wortmannin. In mitotic cells, RAB-A1c is relocated to the cell plate. We revealed that this process could be interrupted by ES1, but not by wortmannin. In addition, root growth and cytokinesis in root mitotic cells of rab-a1a/b/c triple mutant seedlings are hypersensitive to lower concentrations of ES1. ES1 is known to selectively block the transport of several plasma membrane auxin transporters, including PIN2 and AUX1 at the TGN. Together with the known facts that members of Rab-A1 proteins are involved in auxin-mediated responses in root growth and that mutations in TRAPPII, a protein complex that acts upstream of RAB-A1c, also selectively impair the transport of PIN2 and AUX1 at the TGN, we propose that the Rab-A1-mediated trafficking pathways around the TGN, but not Rab-A1s directly, are the target of ES1.
在植物细胞中，Rab-A 蛋白被认为在从高尔基体到质膜/细胞壁的膜运输以及细胞分裂中的新形成的细胞板中发挥重要作用。但是，不同的 Rab-A 蛋白如何在 TGN 中发挥作用尚未得到很好的研究。我们在这里表明，RAB-A1c 定义了 TGN 的一部分，该部分与 VHA-a1 标记的 TGN 部分重叠。有趣的是，RAB-A1c 定义的 TGN 的形态对 endosidin 1（ES1）敏感，但对wortmannin 不敏感。在有丝分裂细胞中，RAB-A1c 被重新定位到细胞板。我们揭示了这个过程可以被 ES1 中断，但不能被 wortmannin 中断。此外，rab-a1a/b/c 三重突变体幼苗的根有丝分裂细胞的根生长和细胞分裂对 ES1 的低浓度更加敏感。ES1 已知选择性地阻断几种质膜生长素转运蛋白的运输，包括 TGN 处的 PIN2 和 AUX1。考虑到 Rab-A1 蛋白参与根生长中的生长素介导的反应的已知事实，以及 TRAPPII（一种作用于 RAB-A1c 上游的蛋白质复合物）的突变选择性地损害 TGN 处的 PIN2 和 AUX1 的运输，我们提出 Rab-A1 介导的 TGN 周围的运输途径，而不是 Rab-A1s 本身，是 ES1 的靶标。
