玉米MSCA1亚家族成员调控茎尖分生组织生长发育和株叶形态的分子机制研究

Plant architecture is one of the crucial determinants for the yield in maize, and plant growth and establishment of the architecture is mainly determined by the shoot apical meristem (SAM) activity. Therefore, understanding the molecular mechanisms of SAM growth will pave the way to optimize maize architecture to higher yield. A previous study from the applicant has shown that a glutaredoxin, MSCA1, regulates SAM growth via a new pathway. However, the related mechanism is not fully understood due to a functional redundancy from its two homologs in the genome. The aim of this project is to: 1). Draw a spatial and temporal expression map of three glutaredoxins by RNA in situ hybridization; 2). Characterize the function of other two homologs in SAM development by analyzing loss-of-function mutants created by CRISPR, and perform phenotypical and genetic analysis of all single/double/triple mutants; 3). Identify the putative interactors or targets of MSCA1 subfamily members by Y2H, and analyze the chemical modification of three glutaredoxins on their putative targets; 4). Creat a transgenic line harboring the modified GFP sensitive to cellular redox state to analyze the effect of mutations in three glutaredoxins on SAM cellular redox state as well as the regulation of cellular redox state on SAM growth. The final goal of this project is to dissect the molecular mechanisms of three glutaredoxins regulating SAM growth and architecture establishment, as well as to get an idea about the effect of cellular redox state on SAM development, to finally supply theoretical bases on optimizing maize architecture for higher yield.

玉米株叶形态是影响产量的关键因素之一，植物生长发育和形态建成直接受到茎尖分生组织(SAM)的控制。解析调控玉米SAM生长发育分子机制将对培育优良株型提供理论指导。申请人前期研究证明谷氧还蛋白MSCA1参与一条新途径调控SAM生长。但因同源基因功能冗余导致对其作用机制认识不够。本项目拟在此基础上：1)利用原位杂交技术建立MSCA1亚家族成员时空表达谱；2)利用CRISPR技术敲除该亚家族其他两个同源基因，对相应突变体进行表型和遗传分析；3)利用酵母双杂交筛选MSCA1亚家族成员的互作蛋白，并鉴定该亚家族蛋白对其靶蛋白的生化调控；4)利用氧化还原敏感型GFP探索MSCA1亚家族成员对SAM氧化还原态的影响，以及细胞氧化还原态对SAM生长发育的调控；以期从遗传、生化及信号传导等方面系统解析MSCA1亚家族成员及体内氧化还原态对SAM生长发育和株叶形态的调控机理，为玉米株型改良育种提供理论基础。

在动物和植物中，谷胱甘肽化是一种常见的蛋白质修饰，它是由一组称为谷氧还蛋白的小蛋白介导的。但是，谷胱甘肽化对植物中靶蛋白活性和功能的调控还知之甚少。本研究项目中，我们显示了CC型谷氧还蛋白MALESTERILE CONVERTED ANTHER1（MSCA1）可以在早期玉米穗发育过程中修饰其可能的靶标，即TGA转录因子FEASCIATED EAR 4（FEA4）。MSCA1早期已确定可控制玉米的茎分生组织大小和叶序，在本研究中我们首先显示它与两个直系同源基因ZmGRX2和ZmGRX5共同调控了穗发育和穗型，深度影响着单株产量。三个基因的功能缺失导致玉米株型矮小，并严重抑制了穗的生长发育。进一步的研究表明，MSCA1可以调节FEA4的氧化还原状态，FEA4是穗发育中的负调控因子。我们的遗传分析表明，FEA4在MSCA1的下游起作用；连同转录组数据，我们的研究发现MSCA1及其直系同源物基因主要通过控制FEA4蛋白的活性和功能来调节花序分生组织大小和穗发育，进而单株产量。