Abstract
The rice virescent mutants (v1, v3) are temperature-conditional and develop chloroplast-deficient leaves under the restrictive temperature. We previously speculated that the virescent genes function at an early stage of leaf development (P4), and are involved in the regulation of chloroplast transcriptional activity. Western blot analysis indicated that in wild-type leaves proteins for plastid transcriptional machinery, including NEP (RpoTp), PEP (RpoA) and the sigma factor (SigA), specifically accumulated at the P4 stages. However, accumulations of these proteins were severely suppressed in the leaves of v1 and v3 mutants. In such mutant leaves, chloroplast proteins encoded in the nucleus (LHCP, RbcS), as well as those encoded in the plastid, barely accumulated at P5 stages. These results suggest that the virescent genes function in the expressions of NEP and PEP, and also suggest that the NEP activation at P4 stage is important for the expression nuclear-encoded genes for chloroplast proteins.
