水稻直立密穗DEP4基因的克隆与功能鉴定

High yield is an eternal topic in rice research, grain number per panicle and grain size are decisive factors for rice yield. However, most varieties with more grain number per panicle are linked by smaller grain size, whereas varieties with larger grain size are restricted by less grain number per panicle. How to balance panicle and grain development is the emphasis and difficulty for rice breeding. So mining and utilization new germplasm resources of panicle type and grain type, and then investigating the possible molecular mechanism, are truly significant in improving rice yield. In this proposal, we have obtained a dense and erect panicle4 (dep4) mutant from a Wuyunjing 7 mutant pool induced by ethylene methylsulfonate (EMS). Compared with wild type, dep4 mutant displayed shorter panicle and grain, enriched primary and secondary rachis branch, and increased the yield per plant obviously. Genetic and allelic analysis indicated that dep4 is a new panicle and grain development mutant, which was controlled by a single recessive gene. The gene was primarily mapped to a 231-kb interval on the long arm of Chromosome 8 using a map-based cloning strategy. Base on these findings, a more fine physical map and sequencing of this interval will be simultaneously carried out to clone the target gene. Subsequently, several DEP4 functional vectors will be transformed into rice to study its biological function. In addition, double mutants and RNA-seq will be employed to screen and analyze the upstream/downstream genes. This study will preliminarily ascertain the genetic and molecular mechanism of DEP4 in rice panicle and grain development, provide theoretical basis for molecular design breeding and germplasm innovation of high yield.

高产是水稻研究的永恒话题，每穗粒数和籽粒大小是决定水稻产量的重要因素。然而，多数穗粒数多的品种籽粒小，籽粒大的品种穗粒数少。因此，“穗粒兼顾”是目前水稻高产育种的重点和难点。挖掘与利用新的穗型和粒型种质资源，揭示水稻穗、粒发育的分子调控机理，对提高水稻产量潜力具有重要意义。本研究前期获得了一个直立密穗突变体dep4，dep4穗和粒均变短、一次和二次枝梗数目增加、单株产量显著提高。遗传分析和等位性分析表明DEP4是一个新的直立密穗隐性基因。已利用图位克隆将其初定位于第8染色体长臂上231 kb的物理区间内。在此基础上，本研究拟扩大群体对该基因进一步精细定位与克隆；构建各种载体转化水稻对DEP4进行功能研究；利用双突变体和表达谱等技术对相关基因进行分析。初步探明DEP4在水稻穗、粒发育过程中的遗传机制及分子调控机理，为分子设计育种，创建水稻高产新种质打下基础。