玉米粒形关键基因遗传调控及互作网络解析

Kernel shape related traits, including kernel's length, width and thickness, directly determine the yield potential in maize. The determination of interactions of kernel shape related genes and the dissection of their genetic regulatory network will be greatly meaningful to the improvement of maize breeding. In this present project, based on the mapping-based cloning of three kernel shape related genes, ZmVps29 (kernel width), ZmqKL9 (kernel length) and ZmUrb2 (kernel thickness) , several types of genetic materials under the same background are going to be developed, including elite haplotype introgression materials, over-expression and gene knock-out materials, as well as two-gene and three-gene pyramiding materials. Then, using integrated approaches of traditional molecular biology, high-throughput analysis of transcriptome, proteome and metabolome, and computational biology, we aim to elucidate the molecular regulatory mechanisms of the aforementioned three kernel shape related genes, and demonstrate their interactions, pyramiding effects, breeding value, as well as establishing genetic regulatory network of kernel shape related genes. The outcomes from the project will provide novel ideas and technologies for the dissection of regulatory network for the complex traits in crops. Meanwhile, in this project, all the primary mapping populations have come from the field breeding practice. Therefore, the discovered elite haplotypes will be easily applied. Finally, the results of this project will also provide theoretical and technical insights to the improvement of the kernel shape related traits in maize.

玉米粒形相关性状（籽粒长、宽、厚）直接影响产量的潜力，阐明粒形关键基因间的互作调控规律，解析其遗传调控网络，可为玉米高产育种的分子设计提供理论基础。基于前期国家基金重大研究计划项目所克隆的玉米粒形主效基因（ZmVps29、ZmqKL9、ZmUrb2等），本集成项目通过创制同一遗传背景的单基因优异单倍型、过表达和基因敲除材料，以及两基因互作和三基因聚合不同类型材料，综合运用分子生物学、多组学和计算生物学等技术手段，阐明玉米粒形3个关键基因的分子调控机理，明确玉米粒形3个关键基因间的相互关系、聚合效应和育种价值，建立玉米粒形多基因遗传调控网络，为农作物复杂性状的遗传调控网络解析提供新的思路和技术方法。本项目中所用的研究材料均来源于育种实践，发掘的优异等位单倍型更容易应用于玉米育种，可为玉米遗传改良过程中粒形三要素的平衡选择提供理论与技术支撑。

籽粒性状关键基因遗传调控网络解析可以为玉米高产分子育种提供重要的理论与技术支撑。本项目综合利用遗传学、分子生物学和生物信息学技术手段，研究玉米粒形关键基因分子调控机理，解析粒形主效基因遗传调控网络，以期为玉米籽粒性状调控机制的深入研究提供支撑。结果表明：（1）过表达ZmVPS29可使籽粒变窄，但单穗产量显著提高；过表达ZmVPS29可以引起生长素相关基因表达发生变化，从而影响生长素在籽粒中的分布；ZmVPS29编码一个液泡分拣蛋白，并可与ZmVPS26a和ZmVPS35a互作，形成复合体共同响应生长素的调控。（2）粒长主效位点ZmKL9的功能基因（EXPB15）编码一个细胞扩展蛋白，可在籽粒珠心组织特异表达；其功能基因的启动子可特异结合转录因子NAC11和NAC29编码蛋白形成的同源二聚体，促进目的基因的高效表达；同时发现，PCD相关基因ICE1编码蛋白可与EXPB15编码蛋白互作，共同参与珠心组织退化，进而影响籽粒的发育。（3）粒厚基因ZmUrb2编码一个核糖体加工蛋白，其突变后导致胚乳中核糖体的生物合成减少，从而影响籽粒的发育；发现玉米35S pre-rRNA的加工同时存在 “5' ETS-first” 和 “ITS1-first” 两条加工路径，而ZmUrb2突变主要抑制35S “ITS1-first” 加工路径中ITS1区域的切割，使35S的加工效率降低，从而影响核糖体的生物合成和籽粒的发育。（4）获得了玉米粒形主效基因优异单倍型的多基因聚合材料，发现多基因聚合材料在玉米籽粒性状上表现出显著的累加效应。（5）开发了多组合加权网络构建和融合的研究方法；利用公共数据构建了以ZmVPS29、ZmKL9和ZmUrb2为节点基因的玉米籽粒多时期遗传调控网络，共鉴定到6303个协同表达基因，包括288个植物籽粒发育同源基因和41个玉米籽粒发育调节相关基因；利用多基因聚合材料在授粉后6天籽粒的表达谱，获得了一个包含4676个基因的玉米籽粒发育调控网络，其中包括148个籽粒发育同源基因及emp7、emp12、ZmSWEET4C、NKD1、Zmzou等玉米籽粒发育相关基因。