水稻新卷叶基因RLC3调控叶形态发育的分子机制解析

叶形态是植物最重要的性状之一；叶形态适度卷曲作为水稻理想株型的一项指标，并有助于提高非生物胁迫抗性，因而在理论和育种上均有研究价值。然而，水稻叶形发育的分子机制仍有待阐明。我们前期研究发现一个新卷叶突变体rlc3，图位克隆表明RLC3基因编码一个功能未知的BELL型Homeobox转录因子，并且RLC3蛋白和KNOX型Homeobox蛋白OSH1/45/71均互作，符合动、植物中已报道的KNOX-BELL复合体模式。本项目拟在此基础上，综合利用基因编辑、遗传转化、突变体分析、蛋白互作以及转录因子等研究策略，系统分析RLC3的生物学功能，期待解析RLC3与OSH1/45/71遗传和分子互作及生物学意义，并探索RLC3-OSH复合体对下游靶基因转录调控机制，从而阐明RLC3调控水稻叶形发育的遗传和分子基础。预期研究结果将揭示叶形态调控新的分子机制，将对水稻叶形遗传改良和利用具有理论意义。

Leaf shape is one of the most important traits for plants. In rice, moderate leaf rolling is considered an important index of ideal plant architecture for many rice breeders and is beneficial for improving the tolerance of plants to abiotic stresses. Thus, leaf rolling is an interesting phenotype for both basic plant research and rice breeding. However, the molecular mechanism underlying leaf rolling remains to be elucidated. Here, we have identified a novel rolling leaf mutant in rice, namely rlc3 (rolling leaf at chromosome 3). Map-based cloning revealed that the RLC3 gene encodes an uncharacterized member of BELL-type homeobox transcription factor. The RLC3 protein contains two highly conserved domains: POX domain and homeobox domain. The rlc3 mutation results in the deletion of homeobox domain in the mutant. The yeast two-hybrid assay revealed that the RLC3 protein had strong interactions with OSH1, OSH45 and OSH71, three members of rice KNOX-type homeobox transcription factor. Such KNOX-BELL interactions are consistent with the previous studies in other plants. Based on these results, a series of approaches including gene editing, genetic transformation, mutant analysis, assays for protein-protein interactions and protein-DNA interactions will be employed to comprehensively investigate the molecular roles of RLC3 in regulating leaf shape development. Furthermore, we will demonstrate the protein-protein interactions between RLC3 and OSH1/45/71 and their biological significance, as well as the transcriptional regulatory mechanism of RLC3-OSH complex in controlling the target gene expression in this project. In sum, our molecular elucidation of RLC3 will reveal a novel molecular mechanism of leaf shape regulation, which will provide theoretical implications for improving the leaf traits in rice breeding.