THE PLANT CELL, Vol 8, Issue 11 2079-2091, Copyright © 1996 by American Society of Plant Biologists
An Arabidopsis Gene Isolated by a Novel Method for Detecting Genetic Interaction in Yeast Encodes the GDP Dissociation Inhibitor of Ara4 GTPase
T. Ueda, N. Matsuda, T. Anai, H. Tsukaya, H. Uchimiya and A. Nakano
Institute of Molecular and Cellular Biosciences, University of Tokyo, Yayoi, Bunkyo-ku, Tokyo 113, Japan
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.
