Baral Anirban, Gendre Delphine, Aryal Bibek, Fougère Louise, Di Fino Luciano Martin, Ohori Chihiro, Sztojka Bernadette, Uemura Tomohiro, Ueda Takashi, Marhavý Peter, Boutté Yohann, Bhalerao Rishikesh P
Department of Forest Genetics and Plant Physiology, Umeå Plant Science Centre, Swedish University of Agricultural Sciences, Umeå 901 87, Sweden.
Laboratoire de Biogénèse Membranaire, UMR5200, Université de Bordeaux, CNRS, Villenave d'Ornon 33140, France.
Plant Cell. 2024 Dec 23;37(1). doi: 10.1093/plcell/koae280.
The trans-Golgi network (TGN), a key compartment in endomembrane trafficking, participates in both secretion to and endocytosis from the plasma membrane. Consequently, the TGN plays a key role in plant growth and development. Understanding how proteins are sorted for secretion or endocytic recycling at the TGN is critical for elucidating mechanisms of plant development. We previously showed that the protein ECHIDNA is essential for phytohormonal control of hypocotyl bending because it mediates secretion of cell wall components and the auxin influx carrier AUXIN RESISTANT 1 (AUX1) from the TGN. Despite the critical role of ECHIDNA in TGN-mediated trafficking, its mode of action remains unknown in Arabidopsis (Arabidopsis thaliana). We therefore performed a suppressor screen on the ech mutant. Here, we report the identification of TGN-localized TYPHON 1 (TPN1) and TPN2 proteins. A single amino acid change in either TPN protein causes dominant suppression of the ech mutant's defects in growth and AUX1 secretion, while also restoring wild-type (WT)-like ethylene-responsive hypocotyl bending. Importantly, genetic and cell biological evidence shows that TPN1 acts through RAS-ASSOCIATED BINDING H1b (RABH1b), a TGN-localized RAB-GTPase. These results provide insights into ECHIDNA-mediated secretory trafficking of cell wall and auxin carriers at the TGN, as well as its role in controlling plant growth.
反式高尔基体网络（TGN）是内膜运输中的一个关键区室，参与从质膜的分泌和内吞作用。因此，TGN在植物生长发育中起关键作用。了解蛋白质如何在TGN处进行分类以进行分泌或内吞再循环对于阐明植物发育机制至关重要。我们之前表明，ECHIDNA蛋白对于下胚轴弯曲的植物激素控制至关重要，因为它介导细胞壁成分和生长素内流载体AUXIN RESISTANT 1（AUX1）从TGN的分泌。尽管ECHIDNA在TGN介导的运输中起关键作用，但其在拟南芥中的作用方式仍不清楚。因此，我们对ech突变体进行了抑制子筛选。在这里，我们报告了TGN定位的TYPHON 1（TPN1）和TPN2蛋白的鉴定。任一TPN蛋白中的单个氨基酸变化都会导致ech突变体在生长和AUX1分泌方面的缺陷受到显性抑制，同时还能恢复野生型（WT）样乙烯响应性下胚轴弯曲。重要的是，遗传和细胞生物学证据表明，TPN1通过RAS相关结合蛋白H1b（RABH1b）发挥作用，RABH1b是一种TGN定位的RAB-GTP酶。这些结果为ECHIDNA介导的TGN处细胞壁和生长素载体的分泌运输及其在控制植物生长中的作用提供了见解。
