一个玉米ZmMs7复等位基因突变体的遗传分析与分子鉴定

Genetic analysis and molecular identification of a multiple allele mutant of ZmMs7 gene in maize

我们在自然群体中发现了一个玉米雄性不育突变体(male sterile mutant),命名为ms20s1。该突变体雄花育性彻底丧失,花药干瘪皱缩,没有花粉形成。细胞学分析发现,与野生型相比,ms20s1突变体花药在S11期表现出明显的药室收缩,绒毡层细胞肿胀,小孢子破裂的表型,表明ms20s1突变体绒毡层细胞程序性死亡出现异常,且花粉败育。遗传分析表明该不育性状受单个隐性核基因控制。为克隆目标基因,以ms20s1为母本分别与不同自交系杂交构建F_(2)定位群体,利用靶向测序技术(GBTS)分析群体基因型,将基因定位于7号染色体124.95-128.47 Mb之间,进一步精细定位将该区间缩小到0.68 Mb。生物信息学分析发现,该区间存在一个已知基因ZmMs7。ZmMs7基因编码PHD-finger转录因子,在绒毡层发育和花粉外壁的形成过程中发挥重要作用。等位测验分析发现ms20s1为ZmMs7基因的等位突变体。基因测序结果表明ms20s1突变体在外显子区存在多处序列变异,与所报道的ZmMs7基因已知突变体ms7-6007和ms7gl的突变方式不同,证明ms20s1是一个新的ZmMs7基因等位突变体。突变体ms20s1的发现与鉴定为探讨玉米核雄性不育的分子机制以及育种应用提供了新的材料。

We identified a maize male sterile mutant in the natural population,designated as ms20s1.The mutant had complete male sterility and lacked pollen grains in the withered anthers.Cytological analysis showed that,compared with the wild type,the ms20s1 mutant exhibited shrinkage locule,swollen tapetum cells,and aborted microspore at S11 stage,indicating that the ms20s1 mutant had abnormal tapetal programmed cell death and complete pollen abortion.Genetic analysis revealed that the male sterility trait was controlled by a single recessive nuclear gene.To clone the target gene,we constructed the F_(2) populations by crossing ms20s1 with different inbred lines and analyzed the population genotype using genotyping by target sequencing(GBTS)techno¬logy.The gene was initially mapped to the 124.95–128.47 Mb region on chromosome 7,and the interval was narrowed down to 0.68 Mb after fine mapping.Bioinformatics analysis indicated that there was one known gene ZmMs7 in this region.The ZmMs7 gene encoded a PHD-finger transcription factor that played an important role in tapetum development and pollen wall formation.Allelism test demonstrated that ms20s1 was an allelic mutant of ZmMs7 gene.Gene sequencing results showed that the ms20s1 mutant had multiple sequence variants in the exon region,which were different from the reported mutants ms7-6007 and ms7gl,confirming ms20s1 was a new allelic mutant of ZmMs7.The discovery and identification of the ms20s1 mutant provide a new material for exploring the molecular mechanism and breeding application of maize genic male sterility.