Rha1, an Arabidopsis Rab5 homolog, plays a critical role in the vacuolar trafficking of soluble cargo proteins.
Rab proteins are members of the Ras superfamily of small GTP binding proteins and play important roles in various intracellular trafficking steps. We investigated the role of Rha1, an Arabidopsis Rab5 homolog, in intracellular trafficking in Arabidopsis protoplasts. In the presence of a dominant-negative mutant of Rha1, soluble vacuolar cargo proteins such as sporamin:green fluorescent protein (Spo:GFP) and Arabidopsis aleurain like protein:GFP are not delivered to the central vacuole; instead, they accumulate as a diffuse or punctate staining pattern within the cell. Spo:GFP at the punctate stains observed in the presence of hemagglutinin:Rha1[S24N] is colocalized with endogenous vacuolar sorting receptor (VSR(At-1)), which is known to localize primarily to the prevacuolar compartment, whereas Spo:GFP in the diffuse pattern is associated with tonoplasts. Furthermore, expression of Rha1[S24N] causes the secretion of a portion of the vacuolar proteins into medium. However, the inhibitory effect of Rha1[S24N] on vacuolar trafficking is relieved partially by coexpressed wild-type Rha1. Based on these results, we propose that Rha1 plays a critical role in the trafficking of soluble cargoes from the prevacuolar compartment to the central vacuole.
Sohn
Eun Ju
EJ
Center for Plant Intracellular Trafficking, Pohang University of Science and Technology, Korea.
Kim
Eol Sun
ES
Zhao
Min
M
Kim
Soo Jin
SJ
Kim
Hyeran
H
Kim
Yong-Woo
YW
Lee
Yong Jik
YJ
Hillmer
Stefan
S
Sohn
Uik
U
Jiang
Liwen
L
Hwang
Inhwan
I
D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000502:physiology; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D017385:Sequence Homology; D022161:Transport Vesicles / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism*; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D020696:rab5 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
D029681:Arabidopsis Proteins; D008164:Luminescent Proteins; D011993:Recombinant Fusion Proteins; C081080:Rha1 protein, Arabidopsis; D049452:Green Fluorescent Proteins; D020691:rab GTP-Binding Proteins; D020696:rab5 GTP-Binding Proteins