Ueda T, Matsuda N, Anai T, Tsukaya H, Uchimiya H, Nakano A
Institute of Molecular and Cellular Biosciences, University of Tokyo, Japan.
Plant Cell. 1996 Nov;8(11):2079-91. doi: 10.1105/tpc.8.11.2079.
The Arabidopsis Ara proteins belong to the Rab/Ypt family of small GTPases, which are implicated in intracellular vesicular traffic. To understand their specific roles in the cell, it is imperative to identify molecules that regulate the GTPase cycle. Such molecules have been found and characterized in animals and yeasts but not in plants. Using a yeast system, we developed a novel method of functional screening to detect interactions between foreign genes and identified this Rab regulator in plants. We found that the expression of the ARA4 gene in yeast ypt mutants causes exaggeration of the mutant phenotype. By introducing an Arabidopsis cDNA library into the ypt1 mutant, we isolated a clone whose coexpression overcame the deleterious effect of ARA4. This gene encodes an Arabidopsis homolog of the Rab GDP dissociation inhibitor (GDI) and was named AtGDI1. The expression of AtGDI1 complemented the yeast sec19-1 (gdi1) mutation. AtGDI1 is expressed almost ubiquitously in Arabidopsis tissues. The method described here indicates the physiological interaction of two plant molecules, Ara4 and GDI, in yeast and should be applicable to other foreign genes.
拟南芥Ara蛋白属于小GTP酶的Rab/Ypt家族，参与细胞内囊泡运输。为了解它们在细胞中的具体作用，必须鉴定调节GTP酶循环的分子。这类分子已在动物和酵母中被发现并进行了表征，但在植物中尚未发现。我们利用酵母系统开发了一种新的功能筛选方法，以检测外源基因之间的相互作用，并在植物中鉴定出这种Rab调节因子。我们发现，ARA4基因在酵母ypt突变体中的表达会加剧突变体表型。通过将拟南芥cDNA文库导入ypt1突变体，我们分离出一个克隆，其共表达克服了ARA4的有害影响。该基因编码Rab GDP解离抑制剂（GDI）的拟南芥同源物，被命名为AtGDI1。AtGDI1的表达互补了酵母sec19-1（gdi1）突变。AtGDI1在拟南芥组织中几乎普遍表达。本文所述方法表明了酵母中两种植物分子Ara4和GDI的生理相互作用，应该适用于其他外源基因。
