水稻茎粗QTL qWS5基因克隆及其分子遗传调控机制解析

The rice yield potential in China has been greatly enlarged in recent years due to the advance of breeding technology, and lodging resistance is becoming a key factor to sustain the high yield loading and a major criterion of new variety development. It has been proved that stem diameter plays an important role in improving the lodging resistance, but studies about the genetic and molecular mechanism underlying the trait are still at the beginning. To resolve the problem, it needs to identify novel genetic factors conferring the trait variation from varieties with strong culms. In our previous studies, three QTLs had been identified from the super rice breeding strain with strong culms and large panicle, and one of them called qWS5 is a novel QTL not clarified before. In the project, we will perform QTL fine-mapping by the heterozygous inbred family (HIF) strategy and validate the underlying gene by complementation test. To fully understand the molecular mechanism of qWS5-mediated stem diameter control, we will clarify the transgenic effect of qWS5 over-expression and knocking out, spatial and temporal expression pattern of qWS5, protein sub-cellular localization, protein interactions and transcriptomic network and the cellular and physiological effect of qWS5 on culms development. Then, we will perform the nucleotide diversity analysis of qWS5 in natural varieties, which will clarify the domestication signature of qWS5 and discover novel superior allele for breeding application. At the same time, we will construct the nearly isogenic lines to combine qWS5 with the other two stem diameter QTLs and clarify the genetic interaction of different loci and the best allele combination in balancing high lodging resistance, high yield and good grain quality, which is important for future super rice breeding. Therefore, this project will generate a significant advance in clarifying the molecular and physiological mechanism of stem diameter control, and lay the theoretical foundation to develop super rice by molecular rational design and provide excellent genetic resources for rice breeding.

随着我国水稻品种产量潜力的不断增加，抗倒伏成为产量稳定及品种选育的关键指标。茎粗是提高水稻抗倒能力的主要性状，然而当前对这一性状的分子调控机制研究仍处于起步阶段，挖掘重要茎粗调控位点是解决这一问题的关键。我们前期研究已成功从超级稻粗秆大穗育种品系中检测到三个主效茎粗QTL，其中qWS5是一个未报道的全新QTL，本项目拟对该位点开展：1、qWS5基因克隆及其分子调控机制研究，包括基因精细定位及功能互补、基因超表达及敲除效应分析、基因表达模式及蛋白定位特征分析、转录组及蛋白互作网络解析、茎粗发育调节的生理生化机制解析；2、qWS5自然品种序列变异类型分析，解析其驯化特征及最优遗传等位；3、qWS5与其余两个茎粗位点的遗传互作分析，寻找三个位点平衡产量、品质及抗倒的最佳组合模式。本研究将快速推动水稻茎粗发育调控理论发展，为超级稻分子设计育种提供重要遗传资源和应用策略。

随着我国超级稻品种的产量潜力不断增加，抗倒伏成为决定产量稳定及品种选育的关键指标。茎粗是提高水稻抗倒能力的主要性状，然而当前对这一性状的分子调控机制研究仍处于起步阶段，挖掘重要茎粗遗传位点成为解决这一问题的关键。我们前期研究已成功从超级稻粗杆大穗育种品系中检测到三个主效茎粗QTL，其中qWS5为尚未克隆的一个QTL。本项目围绕qWS5位点开展了一系列遗传及分子解析工作，具体包括（1）通过重组自交系全面评价了qWS5在扬州和海南种植条件下的茎粗、穗长调控效应，比较了环境效应对QTL表现的影响；（2）利用残余杂合分离群体衍生的不同世代姊妹系有效解析了qWS5区间，发现该区间包括多个控制茎粗和穗长调控位点，最终成功将其主效位点精细定位；（3）成功预测了一个影响穗长的候选基因，并通过群体遗传、超表达及基因敲除手段验证了该基因的效应，明确了该基因的时空表达模式和蛋白亚细胞定位；（4）构建了qWS5与ipa1-2D和qPL6不同等位组合的近等基因系，解析了不同位点组合的遗传效应，探索了关键组合对穗原基发育及下游基因网络的影响，找到了核心调控基因。.通过上述研究，我们发展了一系列高质量的遗传材料，并构建了一套有效的QTL定位及候选基因挖掘策略，为后续开展环境敏感或微效QTL定位提供了借鉴。研究也挖掘了一批可能参与茎粗和穗型调控的核心基因，为后续开展深入的分子调控网络研究打下了基础。.