水稻白穗突变体 ｗp8 的表型鉴定及候选基因定位和功能分析.

[Objectives]Leaf color mutants are excellent materials for studying the photosynthesis and photomorphogenesis of plants. It can be used as an available germplasm resource and it is helpful in hybrid breeding as a marker for removing off-types. The paper aimed to elucidate the molecular mechanism of chloroplast development. [Methods]A rice white panicle 8(wp8)mutant was isolated in the chemical mutagen bank of the japonica variety‘Ningjing 6'. Genetic analysis and map-based cloning of wp8 were performed on an F2 population constructed by wp8 and the indica rice‘N22'hybridization. [Results]Compared with the wild type,the wp8 mutant showed white stripes in the leaves during the vegetative growth period and lasted throughout the following growth stages; the wp8 mutant showed white hulls at the heading stage,but turned yellow when the grains were mature. Compared with the wild type,the contents of photosynthetic pigment in the young leaves,panicle and mature flag leaf of wp8 mutant all significantly reduced. The transmission electron microscope observation of the leaves of the wp8 mutant at the seedling stage and mature stage revealed that most of the chloroplasts of the wp8 mutant were degraded,and the grana lamella in the remaining chloroplasts disappeared while a large number of osmophiles and vacuolar structures emerged. Through genetic analysis and gene mapping,it was found that the wp8 mutation trait was caused by a recessive nuclear gene LOC_Os06g14620 mutation. WP8 was a new allelic gene of ST1(STRIPE1). Quantitative RT-PCR analysis showed that the expression of reactive oxygen species related genes and photosynthetic related genes were both disordered. [Conclusions]The white stripe and white panicle traits of wp8 were caused by the gene mutation on chromosome 6 that encoded a small subunit of ribonucleoside diphosphate reductase. Variations at different sites of WP8 gene had different effects on rice phenotype. The analysis of WP8 gene function will help elucidate the molecular mechanism of chloroplast development. [ABSTRACT FROM AUTHOR]