Tethering factors mediate the initial contact between donor and acceptor membranes. Transport protein particle (TRAPP)III, a multisubunit tethering complex, controls both secretory pathway and autophagy in yeast. However, the roles of TRAPPIII is poorly understood in plants. We have isolated a recessive mutant displaying retarded root growth, defective root hair elongation, and compromised organization of quiescent center by introducing UAS tag in Arabidopsis thaliana and named defective quiescent center (dqc)-1. The tag localized in the 25th exon of At5g16280 encoding AtTRS85 specifying the TRAPPIII complex. Three additional T-DNA insertion mutants of dqc/attrs85 exhibited the defective gravitropic responses in addition to the weak dqc-1-like phenotypes. In dqc-2, the auxin-responsive DR5 expression in the columella was extended and an auxin efflux carrier PIN-FORMED1-GFP abnormally aggregated in the vacuole-like subcellular compartments. In the root epidermis of dqc-2, an early endosome (EE) marker was dispersed in the cytoplasm, a trans-Golgi network (TGN) marker localized in tonoplast, and a vacuole marker localized in the fragmented tonoplast. Furthermore, the endocytosis of FM4-64 in dqc-2 was compromised as evidenced by the decrease in the EE punctum formation, the rapid accumlation into the tonoplast, and the infrequent brefeldin A body formation. Together, DQC/AtTRS85 is essential for the integrity of TGN/EE and the vacuole fusion.

中文翻译：

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缺陷静态中心/ AtTRS85编码反式高尔基体网络/早期内体完整性所需的TRAPPIII特异性亚基对于拟南芥的正确根发育至关重要

束缚因子介导供体和受体膜之间的初始接触。转运蛋白颗粒（TRAPP）III是一种多亚基束缚复合物，可控制酵母的分泌途径和自噬。但是，在植物中对TRAPPIII的作用了解甚少。我们通过在拟南芥中引入UAS标签并命名为缺陷静态中心（dqc）-1，分离出一个隐性突变体，该突变体显示出发育迟缓的根部生长，有缺陷的根毛伸长和静止中心的组织受损。标签位于At5g16280的第25外显子处，编码AtTRS85，指定了TRAPPIII复合体。dqc / attrs85的另外三个T-DNA插入突变体除弱的dqc-1样表型外，还表现出缺陷的重力反应。在dqc-2中，小柱中的生长素应答DR5表达得到延长，并且生长素外排载体PIN-FORMED1-GFP异常聚集在液泡状亚细胞区室中。在dqc-2的根表皮中，早期内体（EE）标记物分散在细胞质中，反式高尔基网络（TGN）标记物位于液泡膜中，而液泡标记物位于碎片化的液泡膜中。此外，dqc-2中FM4-64的内吞作用受到损害，这可通过EE泪点形成的减少，迅速积累到液泡膜中以及不常见的布雷菲德菌素A体形成来证明。一起，DQC / AtTRS85对于TGN / EE和液泡融合的完整性至关重要。