玉米穗发芽突变体vp-like8的遗传分析及突变基因鉴定

Genetic analysis and causal gene identification of maize viviparous mutant vp-like8

玉米突变体vp-like8具有明显的穗发芽性状且能稳定遗传,遗传分析表明该突变性状受隐性单基因控制。用vp-like8与自交系郑58杂交构建F2遗传定位群体,利用BSR-Seq方法,将基因初定在玉米第3染色体160.4 Mb～165.6Mb区间内。参考玉米基因组信息,发现已报道的穗发芽基因Vp1位于此定位区间内。分别利用vp1、vp-like8的杂合突变体进行等位测验,发现杂交后代中正常与穗发芽籽粒符合3∶1遗传分离比。经序列分析,发现vp-like8突变体中Vp1基因在第2内含子有343 bp碱基的缺失,且第3内含子有222 bp重复序列的插入,而已报道的vp1突变体只在第2个内含子有343 bp碱基的缺失。通过实时定量PCR检测发现,与正常籽粒相比, vp-like8与Vp1突变籽粒中Vp1基因的转录水平均明显降低。以上证据表明, vp-like8是一个新的Vp1基因等位突变体。

The maize mutant vp-like8 shows clear viviparous phenotype and stable inheritance,and genetic analysis showed that the mutant phenotype was controlled by a single recessive gene.Using an F2 segregation population derived from vp-like8 and inbred line Zheng 58,the causal gene was mapped to an interval from 160.4 Mb to 165.6 Mb on chromosome 3 by the BSR-Seq technology.According to the maize genomic database,a previously discovered viviparous gene Vp1 was identified to be in this mapping interval.The test crosses from vp1 and vp-like8 heterozygous plants showed a 3:1 segregation ratio between normal and viviparous kernels.The genomic sequence analysis revealed that vp-like8 mutant had a 343 bp deletion in the second intron and 222 bp insertion in the third intron of Vp1 gene,which is different from vp1 mutation of an only 343 bp deletion in the second intron of Vp1 gene.Further real time PCR analysis revealed that,compared with the normal kernels,the transcript level of Vp1 was significantly decreased both in vp-like8 and vp1 viviparous kernels.Taken together,these evidences suggest that vp-like8 is a new allele mutant of Vp1.