MODIFIED VACUOLE PHENOTYPE1 is an Arabidopsis myrosinase-associated protein involved in endomembrane protein trafficking.
ABSTRACT We identified an Arabidopsis (Arabidopsis thaliana) ethyl methanesulfonate mutant, modified vacuole phenotype1-1 (mvp1-1), in a fluorescent confocal microscopy screen for plants with mislocalization of a green fluorescent protein-delta tonoplast intrinsic protein fusion. The mvp1-1 mutant displayed static perinuclear aggregates of the reporter protein. mvp1 mutants also exhibited a number of vacuole-related phenotypes, as demonstrated by defects in growth, utilization of stored carbon, gravitropic response, salt sensitivity, and specific susceptibility to the fungal necrotroph Alternaria brassicicola. Similarly, crosses with other endomembrane marker fusions identified mislocalization to aggregate structures, indicating a general defect in protein trafficking. Map-based cloning showed that the mvp1-1 mutation altered a gene encoding a putative myrosinase-associated protein, and glutathione S-transferase pull-down assays demonstrated that MVP1 interacted specifically with the Arabidopsis myrosinase protein, THIOGLUCOSIDE GLUCOHYDROLASE2 (TGG2), but not TGG1. Moreover, the mvp1-1 mutant showed increased nitrile production during glucosinolate hydrolysis, suggesting that MVP1 may play a role in modulation of myrosinase activity. We propose that MVP1 is a myrosinase-associated protein that functions, in part, to correctly localize the myrosinase TGG2 and prevent inappropriate glucosinolate hydrolysis that could generate cytotoxic molecules.
Article: The VTI family of SNARE proteins is necessary for plant viability and mediates different protein transport pathways.[show abstract] [hide abstract]
ABSTRACT: The Arabidopsis genome contains a family of v-SNAREs: VTI11, VTI12, and VTI13. Only VTI11 and VTI12 are expressed at appreciable levels. Although these two proteins are 60% identical, they complement different transport pathways when expressed in the yeast vti1 mutant. VTI11 was identified recently as the mutated gene in the shoot gravitropic mutant zig. Here, we show that the vti11 zig mutant has defects in vascular patterning and auxin transport. An Arabidopsis T-DNA insertion mutant, vti12, had a normal phenotype under nutrient-rich growth conditions. However, under nutrient-poor conditions, vti12 showed an accelerated senescence phenotype, suggesting that VTI12 may play a role in the plant autophagy pathway. VTI11 and VTI12 also were able to substitute for each other in their respective SNARE complexes, and a double-mutant cross between zig and vti12 was embryo lethal. These results suggest that some VTI1 protein was necessary for plant viability and that the two proteins were partially functionally redundant.The Plant Cell 01/2004; 15(12):2885-99. · 8.99 Impact Factor