水稻HRP调节根系生长作用机理及其农业应用研究

Land plants are mostly anchored to the soil by root. As an important organ of plants, root is not only responsible for water and nutrients absorbing and transporting, but also the biosynthesis place for a number of phytohormones, amino acids and organic acids. With the developing of agronomic biotechnology, it is generally acknowledged that a larger root system would make crops more resistant to lodging, and is essential for increasing the agronomic yield. Previously, we discovered that knocking out the expression of a unknown function gene HRP in rice would inhibit root growth and reduce the crown root initiation, while the roots of transgenic rice that overexpressing HRP are thicker and have more crown root, which suggest that HRP plays critical role in regulating root development. In addition, we found the productivity of individual HRP overexpressing transgenic rice is in average 50% higher than the wild type control, indicating HRP has great potential of increasing agronomic productivity. Therefore, in this proposed study, we plan to use a combination of cell biology, biochemistry and molecular technologies to reveal the molecular mechanisms by which HRP regulating rice root development as well as crown root initiation. We also plan to generate HRP overexpression maize, foxtail mullet and wheat. By systematic evaluation of the root size, agronomic production related phenotypes as well as the water and nutrients deficient responses of these transgenic crops, we will be able to get first hand information about the potential of HRP in future agronomic applications. We believe, by our proposed study, we should be able to reveal a novel mechanism that regulates root development and crown root initiation in rice, and provide useful information for a potential target gene for future breeding of high productive crops.

根是高等植物适应陆地生活衍生出的,吸收和运输水分以及营养物质的主要器官，又是多种激素、有机酸和氨基酸合成的场所，最重要的是帮助植物固着在土壤中。因此有一个庞大而粗壮的根系，是保证作物高产、抗逆、抗倒伏的重要先决条件。实验室前期发现一个水稻功能未知的新基因HRP表达缺失后，根尖分生组织紊乱、冠根和分蘖减少；而过表达后根系粗壮、冠根和分蘖增加，最终导致单株水稻产量增加50％以上，是一个极具生产应用潜力的基因。因此在本项目中，我们拟就HRP调节水稻根生长发育和冠根起始的分子机制展开研究。同时我们也将把HRP同源基因转入玉米、谷子和小麦中，通过对转基因作物的根系、产量性状和耐缺水、营养瘠薄等性状的统计来系统研究HRP在提高作物产量中的应用前景。相信通过本项目的研究，我们将解析水稻根生长发育和冠根起始的新机制，同时也为作物高产抗逆育种提供一个具有重要应用前景的新基因。

水稻是人类的主要粮食作物，其产量易受高温的影响，研究发现全球地表温度平均每升高1度，水稻产量将减少约3.2%。因此，解析水稻的耐高温机制，挖掘调控水稻耐高温的自然位点，对于耐高温水稻品种改良具有重要意义。实验室前期发现OsGBP蛋白的丰度和亚细胞定位均受高温调节。在本研究中，我们构建了OsGBP过表达(OsGBP-OE)、T-DNA和基因编辑突变体，并测试了这些转基因植株对各种胁迫的响应。结果显示OsGBP过表达后能显著提高水稻对环境高温和低温的耐受能力。OsGBP是一个遍在表达的蛋白，尤其在水稻根尖分生区和侧根原基处表达水平较高。OsGBP-OE水稻还表现出不定根变粗（主要原因是皮层细胞变多），不定根数目增加，种子变大、有效穗数和千粒重显著增加等优异农艺性状。OsGBP蛋白在小麦、玉米中高度保守。OsGBP过表达也能让玉米根系变大；单倍型分析结果显示OsGBP的小麦同源基因TaGBP-5B与小麦单株产量和水利用率有关。说明OsGBP表达水平升高能提高作物产量性状，是一份珍贵的作物育种基因资源。为了解释OsGBP调控水稻发育和环境胁迫响应的分子机制，利用酵母双杂交，筛选得到了49个潜在的OsGBP互作蛋白。荧光素酶互补实验和免疫共沉淀技术证实OsGBP可以直接与生长素酰胺水解酶以及OsPIN1s的胞内结构域相互作用。gbp突变体植株中生长素含量增加，而OsGBP-OE突变体植株生长素含量略有下降。然而OsGBP是否通过调节生长素的稳态来调节水稻根的生长发育还有待进一步研究。综上，我们的研究找到了一个能调节水稻、小麦、玉米优良农艺性状的新基因OsGBP。GBP能作为一个新的靶基因位点，为未来作物改良，研发耐高温、高产/稳产的作物品种改良提供了新的遗传操作和品种选育靶位点。

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