Protein Targeting and Vesicular Trafficking
Goh, Tatsuaki , Uchida, Wakana , Takeuchi, Masaki , Ito, Emi , Arakawa, Satoko , Sato, Ken , Ueda, Takashi , Nakano, Akihiko .
AtVps9a, the common activator for two distinct types of Rab5 GTPases, is essential for plant development.
Rab5, a subfamily of Rab GTPases, regulates a variety of endosomal functions as a molecular switch. Arabidopsis thaliana has two different types of Rab5-member GTPases (conventional-type Ara7 and Rha1 and plant-unique-type Ara6). We found that only one guanine nucleotide exchange factor (GEF), AtVps9a, can activate all these Rab5 members to GTP-bound forms in vitro. In the atvps9a-1 mutant, whose GEF activity is completely lost, embryogenesis was arrested at the torpedo stage. GFP-Ara7 and Ara6-GFP were diffused in cytosol like GDP-fixed mutants of Rab5 in atvps9a-1, indicating that the both types are regulated by AtVps9a in vivo. In the leaky atvps9a-2 mutant, elongation of the primary root was severely affected. Overexpression of the GTP-fixed form of Ara7 suppressed the atvps9a-2 mutation, but that of Ara6 had no apparent effects. These results indicate that the two types of plant Rab5 members are functionally differentiated, even though they are regulated by the same activator, AtVps9a.
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1 - The University of Tokyo, Graduate School of Science, Department of Biological Sciences, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan
2 - RIKEN, Discovery Research Institute
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM