水稻外稃形态建成基因的遗传筛选及功能分析

Glume, including palea and lemma, is the unique structures found only in the Peaceae. As the outer floral organ, glume is responsible for protecting kernels and florets from pathogen and insect attack as well as supplying carbohydrates to developing seeds. Meanwhile, the palea and lemma are directly associated with grain yield, because the glume size is one of the determinants of the size of endosperm or grain. However, the molecular mechanism underlying the glume morphogenesis is limited. Previously, we identified a temperature sensitive rice mutant, osrdr6-1, which shows awn-like lemma at high temperature but normal at low temperature. We found that tasiRNAs and phased small RNAs were less accumulation in osrdr6-1 at high temperature. Accordingly, the expression levels of ARF genes, which harbor the targeted sites of tasiRNA, were decreased, thus lead to the lemma defect in osrdr6-1 at high temperature. In this proposal, we will perform suppressor screening of osrdr6-1 and look for mutants back to normal under high temperature. Candidate genes will be identified by map-base cloning combined with genome-wide sequencing. Further functional analysis will reveal the regulatory roles of the identified genes on rice lemma development and help us to understand how plant response to different temperature. Thus, the knowledge of this study will guide breeders to obtain rice variety with better potential for higher yield and more tolerance to high temperature.

颖壳是禾本科植物所特有的花器官，包括内稃和外稃。它们位于小花结构的外层，保护内部器官避免病虫等侵入，提供种子发育所需的营养，同时颖壳大小也是种子大小的决定因素之一，直接决定种子产量。目前有关颖壳形态建成的分子机制了解得十分有限。申请者前期工作鉴定了一个控制水稻外稃发育的温敏突变体osrdr6-1，该突变体在高温条件下外稃发育缺陷而低温下发育正常。在高温条件下，我们发现osrdr6-1中tasiRNA和phased siRNA积累减少，tasiRNA的靶位点ARF基因表达上升并造成外稃发育缺陷。本研究拟以osrdr6-1为材料进行EMS诱变，在高温条件下筛选表型完全或者部分恢复的抑制子(suppressor)，采用图位克隆结合基因组大规模测序技术，鉴定参与水稻外稃形态建成的抑制子基因，通过功能分析阐述其可能的作用机制，完善水稻外稃发育和对环境响应的调控网络,为保证作物高产和稳产提供理论指导。

颖壳是禾本科植物所特有的花器官，保护内部器官避免病虫的侵入，提供种子发育所需的营养，决定种子大小和产量。目前有关颖壳形态建成的分子机制了解得十分有限。本研究以水稻表观遗传因子OsRDR6的温敏突变体（osrdr6-1）为出发点，通过遗传筛选回复osrdr6-1颖壳缺陷的抑制子，鉴定了参与水稻颖壳发育的调控因子，阐明了小分子RNA在颖壳形态建成中的关键调控作用；此外，我们分离鉴定了表观遗传突变体Epi-RAV6和Epi-AK1，并解析了其调控水稻农艺性状的分子机制，进一步证实了表观遗传变异可作为新兴的作物改良途径之一。这两个表观位点的鉴定也为水稻表观遗传编辑体系的建立提供了可用的研究位点。