Abstract
The rice virescent-1 (v1) mutant is temperature-conditional and develops chloroplast-deficient leaves under the restrictive temperature. Positional cloning and structural analyses indicate that V1 encodes a 32 kDa protein that accumulates in chloroplast. C-terminal region of V1 revealed structural similarity to bacterial RNA-binding proteins. V1 protein accumulated abundantly at early P4, and rapidly decreased inversely as contents of leaf chlorophyll and RubisCO increased drastically, but was barely detectable in mature leaves at P5 and P6 stages. V1 accumulation is enhanced largely by low-temperature (20°C), and is suppressed by high-temperature (30°C) treatment. In v1 mutant grown at 20°C, maturation of 16S and 23S rRNA was impaired and precursor rRNAs predominantly accumulated at the P4 leaves. In such v1 mutant, chloroplast translation/transcription capacity were severely suppressed. These observations suggest that V1 is involved in the maturation of chloroplast rRNAs activated in the early P4 stage of leaf development.
