小麦侧根数目主效QTLTaLRN的精细定位与候选基因克隆

Lateral root number is an important agricultural trait. However, there is no related genes were identified in wheat so far. In this proposal, a major QTL of lateral root number was discovered in a RILs population, which was created by a common wheat variety and a common wheat natural mutant (few lateral root). The major QTL explained more than 60% of lateral root number variation, and therefore was named TaLRN . The TaLRN was mapped to a 0.6 cM interval on common wheat chromosome. About 50 putative genes were assigned in this interval according to wheat GenomeZipper. This result give us a great chance to exploit new molecular markers in the interval, and provide new approach to select candidate genes. On the other hand, the residual heterozygous lines were screened from RILs population, and are ready for constructing fine mapping population. Next studies will focus on TaLRN fine mapping, candidate gene(s) cloning and function analysis with taking advantage of wheat genome progress and RNA-seq technology.

侧根数目是重要的农艺性状，小麦中还未有相关基因的报导。本申请项目利用侧根数目极少的小麦自然突变体与普通小麦品系杂交，在其重组自交系群体中发现一个控制侧根数目的主效QTL，可解释群体侧根数目变异的60%以上，命名为TaLRN (Lateral Root Number)。经过遗传图谱加密，目前定位区间已缩小到0.6 cM。利用小麦基因组GenomeZipper分析，已经初步确定定位区间的基因组成。为新标记的开发与候选基因的筛选提供了关键切入点。此外，成功从高代重组自交系群体中筛选得到剩余杂合系，用于构建精细定位的次级分离群体，为精细定位TaLRN奠定了良好的基础。本申请项目拟在此研究基础上，将小麦基因组进展和新技术应用，结合到传统的图位克隆策略中，对控制小麦侧根数目性状的TaLRN进行精细定位、候选基因克隆和作用机理研究。

该项目计划对一个控制小麦侧根发育的主效QTL进行精细定位与克隆。在获得国家基金委面上项目的支持后，进展较为顺利，成功克隆到了该基因。该基因为油菜素内酯途径的关键成员GSK，其保守位点的非同义突变造成了显性负调控的效应。该基因突变抑制侧根突破表皮过程，通过在拟南芥中转入突变形式的TaGSK，证实其在侧根发育中的作用。由于TaGSK在小麦中的功能略有分化，在侧根原基的形成过程中表现出与拟南芥相反的功能，因此小麦的转基因材料仍在在评估中，尚需更多的实验去验证其在小麦中的分化功能。在项目执行期间，发表油菜素内酯调控小麦根系发育论文2篇。同时研究过程发现GSK的突变也造成了小麦耐热性的变化，因此也将项目拓展到小麦的耐热研究，发表相关论文4篇。这些结果有助于持续深入研究小麦根系发育与耐热机理。