Abstract
The rice virescent-2 mutant (v2) is temperature-conditional and develops chlorotic, chloroplast-deficient leaves under restrictive temperature. We cloned the V2 gene and found that the predicted amino acid sequences of V2 gene shared a high degree of homology with known genes encoding guanylate kinase (GUK), an essential enzyme in the nucleotide biosynthesis. The V2 cDNA complemented a yeast GUK-deficient mutant, and the V2-GFP fusion protein was transported to mitochondria. RT-PCR analysis showed that the V2 transcripts highly accumulated at an early stage of leaf development. The expression pattern was consistent with our previous observations that the V2 gene functions at the early stage. We further revealed that, in the v2 mutant, chloroplast translation capacity, raised primarily during this stage, are severely suppressed. These results suggest that GUK activity in mitochondria is essential for the construction of chloroplast genetic system at the early stage of chloroplast development.
