玉米籽粒白化及叶片条斑突变体克隆及功能研究

玉米是三大禾谷类中唯一含有维生素A源的作物，其籽粒富含的类胡萝卜素可参与植物光合电子传递，并具有光保护作用。本研究发现一个玉米籽粒白化突变体wk3537，其籽粒中叶黄素等有色类胡萝卜素及淀粉含量较野生型显著减少，但籽粒总蛋白有所增加。除此之外，突变体叶片在正常光照下呈现黄绿条斑。经BSR-Seq定位及候选区间内基因差异表达分析，结合Mutator转座子标签、EMS诱变及基因编辑技术，克隆并验证了玉米WK3735基因。初步预测该基因定位于叶绿体，可能参与质体类胡萝卜素合成、质体呼吸链电子传递及光保护等生物学途径。此外，在玉米中该基因存在一个高度同源的串联拷贝。本项目拟在现有基础上，对影响籽粒及叶片光合色素含量、质体结构及质体呼吸等进行深入研究，结合外源呼吸抑制、转录组、原位杂交及酵母双杂交等技术，以期解析WK3735影响玉米品质、植株发育的机制及其同源存在的意义，为玉米品质育种提供理论指导。

Maize (Zea mays l.) is the only cereal that contains vitamin A among wheat and rice. Maize seed contains abundant carotenoids, which is essential for photosynthetic electron transport and eliminating the reactive oxygen (ROS) as the photoprotectants in plants. Here, we found a white-kernel mutant (wk3735) with the albinistic-kernel phenotype, further analysis revealed that the lutein, zeaxanthin and other colored carotenoids content was significantly reduced in mutant, while the total grain protein was increased compared with the wild-type. We also observed Nonclonal-leaf stripe of yellow and green in mutant leaves even under normal illumination in the field. The maize WK3735 gene was mapped with BSR-Seq analysis, followed with the differential expressed candidate gene analysis within mapping interval, the target gene WK3735 was validated with the allelic tests of mutants from Mutator-transposon label, EMS mutagenesis and gene editing techniques. It is preliminarily predicted that WK3735 is a chloroplast-located gene and possible involves in carotenoid synthesis, respiration electron transport and photoprotection pathways etc., in plastid. In addition, we found a paralogs of WK3735 with 81% sequence similarity was exists in the same chromosome with the distance of 9.2 Kb in maize, which is different from Arabidopsis, tomato, etc., only exists a single copy. Based on the current study, further study will conducted from two aspects of the alteration of photosynthetic pigment content in grain and the affection of photosystem, such as plastid structure integrity and respiratory electron transfer chain (RETC) in plant leaves, in-depth study with transcriptom analysis, exogenous respiratory depression, in situ hybridization and yeast two hybrid technologies etc., will be used to study the function of WK3735 in photosynthesis and RETC, and further explain the effect of WK3735 on grain quality and plant development and the significance of existed two copies. All the studies will provide a theoretical basis for maize quality breeding.