Rice seed size is an important agronomic trait in determining the yield potential, and four seed size related genes (GS3, GW2, qSW5/GW5 and GIF1) have been cloned in rice so far. However, the relationship among these four genes is still unclear, which will impede the process of gene pyramiding breeding program to some extent. To shade light on the relationship of above four genes, gene expression analysis was performed with GS3-RNAi, GW2-RNAi lines and CSSL of qSW5 at the transcriptional level. The results clearly showed that qSW5 and GW2 positively regulate the expression of GS3. Meanwhile, qSW5 can be down-regulated by repression of GW2 transcription. Additionally, GIF1 expression was found to be positively regulated by qSW5 but negatively by GW2 and GS3. Moreover, the allelic effects of qSW5 and GS3 were detailedly characterized based on a natural population consisting of 180 rice cultivars. It was indicated that mutual interactions exist between the two genes, in which, qSW5 affecting seed length is masked by GS3 alleles, and GS3 affecting seed width is masked by qSW5 alleles. These findings provide more insights into the molecular mechanisms underlying seed size development in rice and are likely to be useful for improving rice grain yield.
水稻籽粒大小是控制產(chǎn)量潛能的重要農(nóng)藝性狀，到目前為止，水稻中已有4個(gè)控制籽粒大小相關(guān)的基因(GS3、GW2、qSW5/GW5和GIF1)被克隆。然而，這4個(gè)基因的相互關(guān)系依然未知，這在一定程度上阻礙了對這些基因在育種中的聚合應(yīng)用。為了研究這4個(gè)基因的關(guān)系，對GS3-RNAi、GW2-RNAi系和qSW5的CSSL進(jìn)行了基因表達(dá)分析。結(jié)果很明顯：qSW5和GW2正調(diào)控GS3，GW2的表達(dá)能夠下調(diào)qSW5的表達(dá)，qSW5正調(diào)控GIF1的表達(dá)，而GW2和GS3負(fù)調(diào)控GIF1的表達(dá)。此外，基于一個(gè)含有180個(gè)水稻品種的自然群體，詳細(xì)分析了qSW5和GS3的等位基因作用，結(jié)果表明這2個(gè)基因之間存在相互作用，qSW5對粒長的作用受到GS3的影響，GS3對粒寬的作用受到qSW5的影響。本研究為更加深入理解水稻籽粒大小發(fā)育的分子機(jī)制及提高水稻產(chǎn)量提供了有用的信息。