Mutations in circularly permuted GTPase family genes AtNOA1/RIF1/SVR10 and BPG2 suppress var2-mediated leaf variegation in Arabidopsis thaliana.
Leaf variegation mutants constitute a unique group of chloroplast development mutants and are ideal genetic materials to dissect the regulation of chloroplast development. We have utilized the Arabidopsis yellow variegated (var2) mutant and genetic suppressor analysis to probe the mechanisms of chloroplast development. Here we report the isolation of a new var2 suppressor locus SUPPRESSOR OF VARIEGATION (SVR10). Genetic mapping and molecular complementation indicated that SVR10 encodes a circularly permuted GTPase that has been reported as Arabidopsis thaliana NITRIC OXIDE ASSOCIATED 1 (AtNOA1) and RESISTANT TO INHIBITION BY FOSMIDOMYCIN 1 (RIF1). Biochemical evidence showed that SVR10/AtNOA1/RIF1 likely localizes to the chloroplast stroma. We further demonstrate that the mutant of a close homologue of SVR10/AtNOA1/RIF1, BRASSINAZOLE INSENSITIVE PALE GREEN 2 (BPG2), can also suppress var2 leaf variegation. Mutants of SVR10 and BPG2 are impaired in photosynthesis and the accumulation of chloroplast proteins. Interestingly, two-dimensional blue native gel analysis showed that mutants of SVR10 and BPG2 display defects in the assembly of thylakoid membrane complexes including reduced levels of major photosynthetic complexes and the abnormal accumulation of a chlorophyll-protein supercomplex containing photosystem I. Taken together, our findings suggest that SVR10 and BPG2 are functionally related with VAR2, likely through their potential roles in regulating chloroplast protein homeostasis, and both SVR10 and BPG2 are required for efficient thylakoid protein complex assembly and photosynthesis.
['Qi|Yafei|Y|', 'Zhao|Jun|J|', 'An|Rui|R|', 'Zhang|Juan|J|', 'Liang|Shuang|S|', 'Shao|Jingxia|J|', 'Liu|Xiayan|X|', 'An|Lijun|L|', 'Yu|Fei|F|']
D049069:ATP-Dependent Proteases D000595:Amino Acid Sequence D017360:Arabidopsis D029681:Arabidopsis Proteins D001483:Base Sequence D002734:Chlorophyll D002736:Chloroplasts D003001:Cloning, Molecular D005453:Fluorescence D020558:GTP Phosphohydrolases D019204:GTP-Binding Proteins D018506:Gene Expression Regulation, Plant D017343:Genes, Plant D005816:Genetic Complementation Test D008565:Membrane Proteins D008969:Molecular Sequence Data D009154:Mutation D019001:Nitric Oxide Synthase D010641:Phenotype D010802:Phylogeny D018515:Plant Leaves D020524:Thylakoids
Leaf variegation Chloroplast development VAR2 Genetic suppressor SVR10/AtNOA1/RIF1