玉米作为主要作物，主要用于饲料，蛋白品质是玉米最重要的营养品质。但一般玉米的蛋白品质较低，改良玉米蛋白品质是长期的育种目标。醇溶蛋白是玉米籽粒最主要的储藏蛋白，约占籽粒总蛋白60%，是玉米蛋白品质的重要决定因素。Opaque2（O2）是已知的最主效的醇溶蛋白转录因子，也是近50年玉米蛋白品质育种中最倚重的育种功能基因。申请人实验室长期从事玉米醇溶蛋白合成调控研究，近两年在O2的下游靶标基因和互作蛋白研究上取得了重要的进展。我们的前期研究发现O2存在磷酸化和泛素化修饰，并取得了较好的前期结果。本研究计划对O2的磷酸化和泛素化修饰开展系统研究，确定修饰位点和修饰类型，分析这些修饰的调控功能和相应机制；并通过寻找上游的修饰因子，探索醇溶蛋白表达调控的可能上游信号通路。本研究将深化醇溶蛋白的表达调控机制，为创制优质蛋白玉米提供理论指导。

Maize is major crop and mainly used as animal feeding. The protein quality is the most important nutritional quality in maize. However, common maize has relative poor protein quality. The improvement of maize protein quality is a long-term goal for maize breeding. Zeins are the prominent storage proteins in maize seeds, account for more than 60% of the total seed proteins, and are the major determining factor for maize seed protein quality. Opaque2 (O2) is the major transcriptional factor for zein genes, and has been used as most important functional target gene in maize protein quality breeding for more than 50 years. The applicant’s lab had years’ research experience on the regulation of zein biosynthesis. In recent years, we have made important progress on the studies of O2 downstream targets and O2 interacting proteins. Our pilot sutdy clearly indicated that O2 has phosphorylation and ubiquitination modifications, and had obtained good preliminary results. In this project, we propose to carry out extensive analysis on the phosphorylation and ubiquitination modifications of Opaque2. We will determine the modification sites and modification types, and characterize their regulatory functions and underlying mechanisms. We will also seek for the corresponding upstream modifiers, and explore the potential upstream signal pathways. This study will expand our understanding about the regulatory mechanisms for zein gene expression, and provide guidelines for future breeding programs on high protein quality maize.