控制水稻穗粒数和株高基因GNH5的克隆及功能分析

Cultivated rice (Oryza sativa L.) was domesticated from wild rice (Oryza rufipogon Griff.), which typically displays fewer grains per panicle. We obtained one introgression line (9WIL148) from a set of introgression lines derived from a cross between indica variety NA93-11 and Hainan Wenchan common wild rice. Compared to NA93-11, 9WIL148 displayed fewer grains per panicle and semidwarf. Using F2 population derived from a cross between 9WIL148 and NA93-11, a major QTL-GNH5 controlling grain number per panicle and plant height was identified in chromosome 5. And we delimited GNH5 to a 11.4 kb region which encompassed only one predict gene. In this study, we are going to verify GNH5 function by genetic transformation, uncover the molecular mechanism through methods in molecular biology and biochemistry, and explore the evolutionary mechanism during rice domestication with analyzing the nucleotide diversity in GNH5 locus in different kinds of cultivated rice and wild rice. Our findings will bring new insight into genetic control of plant height and grain number per panicle, and the molecular mechanisms of yield-related traits improvement during rice domestication, and also provide new gene resources in the breeding of high-yielding rice.

普通野生稻是亚洲栽培稻的祖先种，它的穗粒数要明显少于栽培稻。申请者所在课题组前期从以无芒93-11（NA93-11）为背景的海南文昌野生稻渗入系中，筛选出穗粒数和株高均明显低于NA93-11的渗入系9WIL148。利用9WIL148与NA93-11杂交得到的F2群体，在5号染色体发现一个控制水稻穗粒数及株高的QTL-GNH5，并进一步利用分离群体，将GNH5精细定位在11.4kb的区间内，该区间只有一个预测基因。本项目将通过转基因验证候选基因的功能，利用分子生物学、生物化学等方法研究其调控水稻穗粒数及株高的分子机制；通过测序分析不同野生稻材料及栽培稻品种GNH5位点的变异，结合单倍型分析和关联分析，探究在栽培稻驯化过程中该位点的进化机制。该研究不仅为揭示水稻穗粒数和株高的遗传调控机理及栽培稻产量性状驯化的分子机理提供新线索，也为水稻高产育种提供新的基因资源。

穗粒数是决定水稻产量高低的最重要因素之一，克隆控制穗粒数的关键基因，解析其调控的分子机制对于水稻高产育种具有重要意义。本项目利用两个普通野生稻的渗入系，鉴定了一个控制水稻穗粒数和株高的重要基因GNH5，GNH5编码赤霉素合成途径中的一个关键酶，其启动子区两个关键碱基的变化能够增加该基因的表达，从而提高植物体内活性赤霉素的含量，增加穗粒数和株高。进化分析表明，该基因在籼稻和粳稻之间存在明显分化，籼稻育种过程中该基因受到了人工选择。此外，还鉴定了一个控制株型和穗型的新基因TAC4，该基因通过影响生长素的含量与分布来调控水稻的株型。研究结果不仅为揭示水稻产量相关重要性状的分子机理提供重要参考，而且为水稻分子设计育种提供潜在的基因资源。