Abstract
The rice virescent-2 mutant (v2) is temperature-conditional and develops chlorotic leaves under the restrictive temperature. Previous studies speculated that the V2 gene functions at an early stage of leaf development (P4), and is involved in the regulation of expression of the plastid-encoded genes. We isolated the V2 gene using a map-based cloning approach. V2 gene exhibited an extensive sequence similarity to the genes encoding guanylate kinase (GUK), an essential enzyme in the biosynthesis of nucleotides. We confirmed that the V2 gene (designated ogkA) complements the yeast guk1 mutation. RT-PCR analysis showed that the ogkA transcripts highly accumulated in the immature leaves at stages from P1 to P4. These results suggest that the functional activation of OgkA, a part of nucleic acid metabolism, is a key process in the early chloroplast biogenesis, and this process may be involved in the construction of chloroplast genetic system.
