Figure 8.
Model for the Role of Rha1 in Vacuolar Trafficking.
The observation that Spo:GFP and RFP:Rha1[S24N] at the punctate stains colocalize with VSRAt-1 imply that Rha1 localizes to the PVC. In support of this notion is our preliminary observation that transiently expressed Rha1 in protoplasts gave a punctate staining pattern and colocalized with VSRAt-1 and AtPEP12p, two proteins known to localize to the PVC (E. Sohn and I. Hwang, unpublished data). However, the exact localization of Rha1 needs to be confirmed further. Rha1 could play roles at the PVCs (or endosomes) through its involvement in the fusion of PVCs (or endosomes) or the fusion of endosomes to the central vacuole (i) or in the fusion of vesicles derived from PVCs (or endosomes) to the central vacuole (ii). In the first scenario, we hypothesize that Rha1 recruited to the PVC may be involved directly in the fusion of the PVC to the tonoplast. In the second scenario, we hypothesize that Rha1 recruited to the PVC (or endosome) may be transferred to a vesicle that carries cargo proteins and travel with the vesicle to the tonoplast, where it is involved in the fusion of the vesicle to the tonoplast. TGN, trans-Golgi network.