The biological roles of small GTPases and interacting proteins in plants

Uchimiya, Hirofumi; Anai, Toyoaki; Aspuria, Evalour T.; Matsui, Masanao; Nakano, Akihiko; Ueda, Takashi

doi:10.1007/bf02512180

Cited by 11 publications

(8 citation statements)

References 14 publications

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“…The hypervariable region is also known to play a critical role in determining the subcellular localization of each protein (Chavrier et al ., 1991; Brennwald and Novick, 1993). To date many Rab GTPases have been identified from higher plants (Ma, 1994; Verma et al ., 1994; Uchimiya et al ., 1998). Ara is the name given to a group of Rab GTPases from Arabidopsis thaliana .…”

Section: Introductionmentioning

confidence: 99%

Ara6, a plant-unique novel type Rab GTPase, functions in the endocytic pathway of Arabidopsis thaliana

et al. 2001

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Ara6 of Arabidopsis thaliana is a novel member of the Rab/Ypt GTPase family with unique structural features. It resembles Rab5 GTPases best, but lacks a large part of the C-terminal hypervariable region and the cysteine motif, and instead harbors an extra stretch of amino acid residues containing myristoylation and palmitoylation sites at the N-terminus. Ara6 is tightly associated with membranes and is expressed constitutively. In contrast, the conventional Rab5 ortholog, Ara7, is highly expressed only in actively dividing cells. Examination of green fluorescent protein (GFP)-tagged proteins indicates that both Ara6 and Ara7 are distributed on a subpopulation of endosomes and suggests their roles in endosomal fusion. The endosomal localization of Ara6 requires N-terminal fatty acylation, nucleotide binding and the C-terminal amino acid sequence coordinately. Proteins similar to Ara6 are found only in higher plants and thus represent a novel class of Rab GTPases regulating endocytic function in a plant- specific manner.

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Section: Introductionmentioning

confidence: 99%

Ara6, a plant-unique novel type Rab GTPase, functions in the endocytic pathway of Arabidopsis thaliana

et al. 2001

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“…In higher plants, many homologues of these GTPases have been identified (for reviews, see Ma, 1994; Terryn et al . 1993 ; Uchimiya et al . 1998 ; Verma et al .…”

Section: Introductionmentioning

confidence: 99%

A dominant negative mutant of Sar1 GTPase inhibits protein transport from the endoplasmic reticulum to the Golgi apparatus in tobacco and Arabidopsis cultured cells

et al. 2000

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SummaryProtein secretion plays an important role in plant cells as it does in animal and yeast cells, but the tools to study molecular events of plant secretion are very limited. We have focused on the Sar1 GTPase, which is essential for the vesicle formation from the endoplasmic reticulum (ER) in yeast, and have previously shown that tobacco and Arabidopsis SAR1 complement yeast sar1 mutants. In this study, we have established a transient expression system of GFP-fusion proteins in tobacco and Arabidopsis cultured cells. By utilizing confocal laser scanning microscopy, we demonstrate that a dominant negative mutant of Arabidopsis Sar1 inhibits the ER-to-Golgi transport of Golgi membrane proteins, AtErd2 and AtRer1B, and locates them to the ER. The same mutant Sar1 also blocks the exit from the ER of a vacuolar storage protein, sporamin. These results not only provide the ®rst evidence that the Sar1 GTPase functions in the ER-to-Golgi transport in plant cells, but also prove that conditional expression of dominant mutants of secretory machinery can be a useful tool in manipulating vesicular traf®cking.

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“…1991 ; Matsui et al . 1989 ; Uchimiya et al . 1998 ), among which Ara4 is localized around the Golgi region ( Ueda et al .…”

Section: Introductionmentioning

confidence: 99%

Modes of interaction between the Arabidopsis Rab protein, Ara4, and its putative regulator molecules revealed by a yeast expression system

Ueda¹,

Matsuda²,

Uchimiya³

et al. 2000

The Plant Journal

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SummaryAra4, a member of the Rab/Ypt GTPase family derived from Arabidopsis thaliana, causes severe growth inhibition when expressed in several yeast ypt mutants. Mutational analysis of ARA4 indicated that the Ara4 protein titrates at least three factors in yeast, including the GDP dissociation inhibitor (GDI). The coexpression of AtGDI1 (Arabidopsis GDI) suppressed the growth defect caused by Ara4 in yeast ypt1, suggesting that Ara4 and AtGDI1 interact in yeast to compensate for the titration of yeast GDI. We screened an Arabidopsis cDNA library for other suppressors that may also interact with Ara4 physiologically. A novel suppressor, SAY1, encoded a hydrophilic protein with two putative coiled-coil regions, which showed partial similarity to the yeast Vps27 protein. To understand the structural requirements of Ara4 for interacting with these molecules, we examined whether AtGDI1 and SAY1 could suppress the growth defect of ypt1 caused by various mutant versions of ARA4. The results indicated that the interaction between Ara4 and AtGDI1 depends on the conserved C-terminal Cys-motif and Thr44 in the effector domain of Ara4. In contrast, neither of these motifs is necessary for the interaction between Say1 and Ara4. This approach provides a powerful method to dissect complex interactions between a GTPase and its regulators.

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The biological roles of small GTPases and interacting proteins in plants

Cited by 11 publications

References 14 publications

Ara6, a plant-unique novel type Rab GTPase, functions in the endocytic pathway of Arabidopsis thaliana

Ara6, a plant-unique novel type Rab GTPase, functions in the endocytic pathway of Arabidopsis thaliana

A dominant negative mutant of Sar1 GTPase inhibits protein transport from the endoplasmic reticulum to the Golgi apparatus in tobacco and Arabidopsis cultured cells

Modes of interaction between the Arabidopsis Rab protein, Ara4, and its putative regulator molecules revealed by a yeast expression system

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