水稻株型和穗型的分子遗传调控网络

Both plant architecture and inflorescence architecture are key agronomical factors determining grain yield in rice. Identification of the genes controlling these two traits and construction of the genetic regulatory networks they involved in will establish important theoretical foundation for shaping ideal plant architecture and breeding of high-yield rice varieties. We identified two genes CAD1 and HQ7 that play important roles in regulating plant architecture and inflorescence architecture. CAD1 and HQ7 inhibit tillering, promote panicle branches development, increase grain number per panicle and subsequently enhance grain yield through modulating auxin in rice. On this basis, we will utilize single gene and multiple genes transgenic plants of CAD1 and HQ7 to further dissect the molecular mechanisms of CAD1 and HQ7 at the levels of transcription, protein and hormone metabolism. We will identify the downstream interactive genes of CAD1 and HQ7, and develop the genetic networks regulating plant architecture and inflorescence architecture which is mediated by auxin. This work will be helpful for revealing the complex genetic regulatory network controlling plant architecture and inflorescence architecture, and also provide new genes and techniques to improve rice plant architecture and to enhance grain yield in rice.

株型和穗型是两个影响水稻产量的重要农艺性状，它们是多基因控制的复杂数量性状。克隆控制水稻株型和穗型的关键基因，构建其参与的遗传调控网络，将为塑造水稻理想株型、培育高产水稻品种奠定重要的理论基础。本项目申请人及共同申请人克隆了两个控制水稻株型和穗型重要基因CAD1和HQ7。CAD1和HQ7基因均通过生长素抑制分蘖生长，促进枝梗发育，增加每穗粒数，最终提高单株产量。本项目拟在此基础上，以CAD1和HQ7基因分别和同时过量表达、下调表达转基因植株等遗传材料为研究对象，利用分子生物学技术，在转录水平、蛋白水平和激素代谢水平，进一步研究CAD1和HQ7的功能，鉴定CAD1和HQ7的下游互作基因，构建CAD1和HQ7基因共同参与、由生长素所介导的水稻株型和穗型遗传调控网络，研究结果不仅为构建水稻株型和穗型的遗传调控网络提供重要基础，而且为改良水稻株型和提高产量提供新基因和新技术。

株型和穗型是两个影响水稻产量的重要农艺性状，克隆控制水稻株型和穗型的关键基因，构建其参与的遗传调控网络，将为塑造水稻理想株型、培育高产水稻品种奠定重要的理论基础。本项目在前期工作基础上，进一步研究了控制株型、穗型基因重要基因PAY1和HQ7的功能，并且克隆了4个控制水稻穗粒数和产量新基因。发现HQ7属于auxin-signaling F-Box (AFB)基因家族（OsAFB6），过表达HQ7/OsAFB6基因的突变体和转基因系均表现抽穗延迟，枝梗和颖花数增多，产量提高。在穗发育基因FZP的上游5.3 kb处的18bp插入降低FZP基因的表达，增加穗粒数、提高产量，有意思的是，PAY1能够与FZP在体内能够形成蛋白复合体，促进FZP蛋白的降解，并且突变的PAY1能够提高其水解效率。此外，我们还克隆了控制穗粒数基因NOG1、GN2和GAD1，GN2是一个新形成的基因，可能通过赤霉素途径调控水稻穗粒数。NOG1基因编码脂肪酸β-氧化途径中烯酰辅酶A水合酶，其启动子区域的一个12-bp的插入能够增加基因的表达水平，降低植物体内脂肪酸和茉莉酸的水平，增加穗粒数，提高产量。GAD1编码一个富含半胱氨酸的小分子分泌肽，提高影响细胞分裂素的水平影响穗粒数、籽粒大小及芒的发育。以上研究结果不仅为解析水稻穗粒数与产量的遗传调控网络提供了一个新的突破，也为水稻高产育种提供了重要新基因。

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