一个新的玉米显性矮秆基因的克隆与功能验证

In recent years, maize lodging happened frequently, which influenced the yield and quality of maize seriously. The creation and screening of new dwarf germplasm resources and functional analysis of related genes is of great theoretical and practical significance in the lodging resistance breeding. We found a dominant mutant gene Dt, and made a pilot study in dwarfing mechanism and fine mapping. The results were as follows: (1) In segregation population, the height of dwarf individual plants had one more internode compared with high individuals on average. Cytological observation revealed that the internodes were shortened as the cells length in dwarf individuals stem was inhibited.（2）We mapped Dt gene in one BAC with 0.2 cM of genetic distance between the two closest markers. The physical distance was about 68 Kb and contained three ORFs and one of them named ZmDt was postulated to be the the dwarf gene. This study is to isolate the dwarf gene ZmDt, to prove its function and to discuss the relation of plant hormones and the ZmDt gene. This project will lay a solid foundation for analyzing the molecular mechanism of ZmDt gene in controlling the stem development and for creating new dwarf gene resources used in maize plant type breeding.

近年来，玉米大面积倒伏现象时有发生，严重影响了玉米的产量和品质。创造或筛选新的矮秆资源，分离相应基因和研究其功能，对培育矮秆抗倒玉米品种具有重要的理论和实践意义。我们筛选到一个由显性单基因控制的矮秆突变基因Dt，对其矮化机理进行了初步研究并对Dt基因进行了精细定位，结果表明：（1）矮秆植株比高秆植株平均多一个节间，矮秆植株的节间为均匀缩短，节间缩短是由于细胞伸长受到了抑制；（2）采用图位克隆法将Dt基因定位于一个BAC上，两端标记相距0.2 cM，物理距离约为68Kb，其间有3个ORF,确定其中的ZmDt为矮秆基因。本研究在此基础上，分离具有自主知识产权的矮秆基因ZmDt并验证其功能，探讨植物激素与ZmDt基因的关系，为进一步分析和明确ZmDt基因调控茎秆发育的分子机理奠定基础，并创造玉米新的矮秆基因资源，用于玉米株型分子育种。

倒伏现象严重影响了玉米的产量和品质，创造和筛选新的矮秆资源，分离相应基因和研究其功能，对培育矮秆抗倒玉米品种具有重要的理论和实践意义。在前期研究的基础上对具有自主知识产权的矮秆基因Dt进行了研究，石蜡切片和扫描电镜技术观察发现矮杆突变体茎节间的细胞伸长明显受到抑制，从而使得茎节间缩短，株高降低，而dt的横向宽度显著增加；外施激素和激素含量测定表明高浓度的ACC是导致显性矮秆突变体株高降低的原因；通过精细定位确定了候选基因ZmACS7，该基因编码了ACC（1-氨基环丙烷-1-羧酸）合酶。突变体在突变区域附近发生过DNA重组,突变区域的上游序列与Mo17相同，下游序列与B73相同。在ZmACS7靠近3’UTR的位置有一个大小为205bp的片段插入，插在ZmACS7的第四个外显子末端；亚细胞定位结果表明基因编码蛋白位于细胞质内；过表达和Cas9敲除的T0植株都发生了株高矮化，为验证此基因的功能和创造玉米理想株型材料应用于育种奠定了基础。