小麦产量性状基因TaMYB-7A功能鉴定及其调控机制研究

Bread wheat (Triticum aestivum. L) is an allohexaploid species and the extremely large genome makes it difficult to isolate yield related genes. The main challenge facing us is to fully characterize the gene networks associated with yield traits formation and identify key genes for higher yield. Based on the previous research, we found a QTL associated with tiller number, grain number, 1000-grain weight and other yield related traits on chromosomes 7A in wheat, named QYt.crc-7A. With comparative genomics and bioinformatics methods, QYt.crc-7A was co-located with a yield related QTL on chromosome 2 in rice, containing a MYB transcript factor (Os02g04640). It indicated that TaMYB-7A, a putative ortholog of the rice MYB, play a functional role on wheat yield. Haplotype/trait association analysis using Chinese wheat mini core collection revealed that TaMYB-7A was significantly associated with grain number per spike, 1000-grain weight and spike length. Overexpression of TaMYB-7A in Arabidopsis thaliana and rice produced pleiotropic effects during vegetative and reproductive development and enhanced yield per plant. These results suggest that TaMYB-7A plays an important role in wheat yield determination. This project plans to analysis function and regulation mechanism through expression analysis, subcellular localization, transgenic wheat, and EMSA. The research will contribute to further understanding of the pathway and mechanisms of TaMYB-7A. In addition, the functional marker for TaMYB-7A will be developed for high-yield MAS breeding in wheat. This study will provide the theoretical bases and technical approaches to mine genes of important agronomic trait from wheat.

发掘和克隆产量基因并解析其调控机制可加快小麦遗传改良进程。然而，小麦产量基因克隆的报道却十分有限。前期发现小麦7A染色体上存在一个控制穗粒数和千粒重等产量性状的QTL，利用比较基因组学和生物信息学方法选择TaMYB-7A为该QTL的候选基因。连锁分析和关联分析证明TaMYB-7A与穗粒数、穗长和千粒重等产量性状显著关联。此外，转基因拟南芥营养生长增强、果荚数目和长度增加；转基因水稻生长势和单株产量也显著高于对照。研究表明：TaMYB-7A可能是一个新的产量相关基因。在此基础上，拟采用转基因、酵母互作和EMSA等分子生物学技术结合不同群体表型/基因型的差异研究TaMYB-7A的生物学功能，揭示该基因调控产量性状的作用机制；再通过亚细胞定位和酵母激活等方法明确TaMYB-7A的转录特性；并开发功能标记。研究结果有助于解析小麦产量性状的分子机制，丰富小麦重要农艺性状基因挖掘的理论基础和技术方法。

磷是植物生长发育所必需的营养元素，培育磷高效作物对于农业的可持续发展至关重要。本项目在小麦7A染色体QTL区段克隆了TaMYB-7A，为磷代谢和磷饥饿响应调节基因OsPHR3的同源基因。在水稻和拟南芥中过表达TaMYB-7A可促进植株生长，提高籽粒数量；水稻过表达株系生物量、穗粒数和小穗数分别增加了48.2%、24.6%和31.7%，且未发现磷中毒的现象。通过转基因小麦RNAi干扰，发现在不同磷含量的生长条件下，降低该基因表达量均抑制了苗期的生长和根毛形成，成株期显著降低株高、小穗数和穗粒数，说明TaMYB-7A正调控植株对低磷的敏感性；导入系进一步验证该基因调控小麦穗粒数的形成和发育，且TaMYB-7A-A为优异单元型。TaMYB-7A亚细胞定位在细胞核表达，P1BS-Like在下游基因识别P1BS功能结构域过程中不可或缺。TaMYB-7A影响Ta-IPS1.1、Ta-IPS1.2、Ta-SPX3 和Ta-MGD2等已知磷饥饿响应基因，进一步证明TaMYB-7A在缺磷响应过程中发挥着重要作用。采用关联分析和连锁分析发现TaMYB-7A-A优异等位变异在育种过程中受到了正选择效应，dCAPS标记可作为选育高小穗数和穗粒数的有效分子标记。研究结果为农作物耐低磷品种培育提供了有利的选择靶点及分子标记。