Grain weight is a major determinant of crop grain yield and is controlled by naturally occurring quantitative trait loci (QTLs). We earlier identified a major QTL that controls rice grain width and weight, GW5, which was mapped to a recombination hotspot on rice chromosome 5. To gain a better understanding of how GW5 controls rice grain width, we conducted fine mapping of this locus and uncovered a 1 212-bp deletion associated with the increased grain width in the rice cultivar Asominori, in comparison with the slender grain rice IR24. In addition, genotyping analyses of 46 rice cultivars revealed that this deletion is highly correlated with the grain-width phenotype, suggesting that the GW5 deletion might have been selected during rice domestication. GW5 encodes a novel nuclear protein of 144 amino acids that is localized to the nucleus. Furthermore, we show that GW5 physically interacts with polyubiquitin in a yeast two-hybrid assay. Together, our results suggest that GW5 represents a major QTL underlying rice width and weight, and that it likely acts in the ubiquitin-proteasome pathway to regulate cell division during seed development. This study provides novel insights into the molecular mechanisms controlling rice grain development and suggests that GW5 could serve as a potential tool for high-yield breeding of crops.
粒重是決定作物產(chǎn)量的主要因素，受自然產(chǎn)生的數(shù)量性狀基因座控制。早期我們鑒定到了一個(gè)控制水稻粒寬和粒重的主效QTL GW5，它定位在水稻5號染色體的重組熱點(diǎn)中。為了深入研究GW5如何控制水稻的粒寬，我們對其進(jìn)行了精細(xì)定位。與細(xì)粒品種IR24相比，寬粒品種Asominori中GW5位點(diǎn)發(fā)生了1212bp片段的缺失。另外，對46個(gè)水稻品種進(jìn)行基因型分析發(fā)現(xiàn)這一缺失與粒寬表型緊密連鎖，表明GW5的缺失在水稻人工馴化過程可能被選擇。GW5編碼一個(gè)新的核蛋白，蛋白長度為144個(gè)氨基酸，定位在細(xì)胞核內(nèi)。我們進(jìn)一步發(fā)現(xiàn)GW5在酵母雙雜交實(shí)驗(yàn)中可以與泛素多聚體互作。綜合以上結(jié)果我們認(rèn)為GW5是控制水稻粒寬和粒重的主效QTL，它可能通過泛素蛋白酶體途徑在種子發(fā)育過程中調(diào)節(jié)細(xì)胞的分裂。我們的研究結(jié)果為闡明控制水稻種子發(fā)育的分子機(jī)理提供了新的見解，同時(shí)GW5還可以應(yīng)用與作物的高產(chǎn)育種。
結(jié)果：細(xì)粒染色體替換系CSSL28的鑒定；GW5與Asominori品種中1212bp片段的缺失連鎖；寬粒品種中廣泛存在1212bp片段的缺失，可能是一個(gè)人工馴化相關(guān)基因；GW5在細(xì)粒品種中表達(dá)；GW5與泛素多聚體互作。