SG3蛋白调控水稻株型和粒型的分子生物学功能研究

Rice architecture and grain size directly affects the effective panicle number and 1000-grain weight, are significant for enhancing rice yield, however, its molecular mechanism remains unknown. In our preliminary study, we identified a mutant, sg3, which showed reduced plant height, lamina joint inclination and grain length from the mutant library generated from the core parent of heavy panicle hybrid rice--Shuhui498. Gene mapping and RNAi results indicated that the phenotype of sg3 was controlled by a nonsynonymous mutation in a kinase protein, this mutation was located at the kinase domain. The mutant of SG3 homolog in Arabidopsis showed no obvious phenotype, whereas, the other gene in its family was reported to be involved in BR signal transduction by interacted with BRI1. The plant architecture and grain size of sg3 was similar to the BR receptor-like kinase mutant, osbak1. The yield of sg3 was significantly increased under compact planting condition. Based on these preliminary data, we plan to dissect the molecular biology function of SG3 regarding plant architecture and grain size, investigate the relationships of SG3 with OsBRI1 or OsBAK1, understand the yield potential of sg3 under compact planting condition. Our result will provide gene resource and theoretical basis for revealing the molecular regulatory networks of rice architecture and grain size, and for improving yield by regulating rice architecture and grain size.

水稻株型和粒型直接影响单位面积有效穗和千粒重，对提高水稻产量具有重要意义，但其分子机制尚不清楚。我们从重穗型杂交稻骨干亲本蜀恢498突变体库中鉴定了一份株高略低，粒长和叶夹角减小的突变体sg3。基因定位和RNAi结果表明sg3表型由一个激酶蛋白中单氨基酸改变引起，该突变位点位于SG3激酶结构域，拟南芥同源基因突变体无明显表型，但该家族另外一个基因被报道与BRI1互作参与BR信号转导，sg3株型和粒型与BR类受体激酶突变体osbak1表型相似，且sg3对外源BL处理表现为顿感，密植sg3比野生型产量显著提高。本项目在上述研究基础上，拟深入解析SG3调控水稻株型和粒型发育的分子生物学功能，解析SG3与OsBRI1和OsBAK1的相互关系，明确sg3通过密植提高水稻产量的应用潜力，为全面揭示水稻株型和籽粒发育的分子调控网络以及通过调控水稻株型和籽粒大小提高水稻产量提供基因资源和理论。

粒型是直接决定水稻产量的重要性状，但是调控粒型的遗传和分子机制还很不清楚。本项目中，我们鉴定到一个粒型和千粒重相关的突变体，命名为grain length and grain weight 10 (glw10)，该突变体表现为粒长和千粒重显著降低。组织细胞学分析表明GLW10通过影响细胞扩张调控粒型。通过MutMap定位方法和转基因试验验证确定GLW10编码一个BR信号激酶，OsBSK2。OsBSK2编码一个质膜蛋白，其N端豆蔻酰化位点对其膜定位和功能是必须的。OsBSK2与BR受体激酶OsBRI1直接互作，但是遗传实验表明OsBSK2调控粒型是独立于BR信号途径的。OsBSK2能形成同源二聚体，以及与OsBSK3和OsBSK4形成异源二聚体，并且OsBSK2，OsBSK3，OsBSK4的干涉植株均表现出小粒表型，说明水稻中BSK基因可能通过形成同源或异源二聚体的形式正调控粒型和千粒重。与其调控粒型的生物学功能一致的是这些基因都在发育中的幼穗和颖壳中高表达。综上，我们的研究结果揭示了水稻中BSK基因新的生物学功能，为作物粒型改良提供了新的靶基因。

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