Abstract：
Male sterility provides an efficient approach for commercial exploitation of heterosis. Despite more than 20 genic male sterile (GMS) mutants documented in pepper (Capsicum annuum L.), only two causal genes have been successfully identified. Here, a novel spontaneous recessive GMS mutant, designated msc-3, is identified and characterized at both phenotypic and histological levels. Pollen abortion of msc-3 mutant may be due to the delayed tapetum degradation, leading to the non-degeneration of tetrads callosic wall. Then, a modified MutMap method and molecular marker linkage analysis were employed to fine mapping the msc-3 locus, which was delimited to the ~139.91-kb region harboring 10 annotated genes. Gene expression and structure variation analyses indicate the Capana10g000198, encoding a R2R3-MYB transcription factor, is the best candidate gene for the msc-3 locus. Expression profiling analysis shows the Capana10g000198 is an anther-specific gene, and a 163-bp insertion in the Capana10g000198 is highly correlated with the male sterile (MS) phenotype. Additionally, downregulation of Capana10g000198 in male fertile plants through virus-induced gene silencing resulted in male sterility. Finally, possible regulatory relationships of the msc-3 gene with the other two reported pepper GMS genes, msc-1 and msc-2, have been studied, and comparative transcriptome analysis reveals the expression of 16 GMS homologs are significantly downregulated in the MS anthers. Overall, our results reveal that Capana10g000198 is the causal gene underlying the msc-3 locus, providing important theoretical clues and basis for further in-depth study on the regulatory mechanisms of pollen development in pepper.
摘要：
雄性不育为杂种优势的商业化开发提供了有效途径。尽管辣椒（CapsicumannuumL.）中记录了20多个基因雄性不育（GMS）突变体，只有两个因果基因被成功鉴定。这里,一种新的自发隐性GMS突变体，命名为msc-3，在表型和组织学水平上进行鉴定和表征。msc-3突变体的花粉败育可能是由于绒毡层降解延迟，导致四分体纤维壁不退化。然后，改进的MutMap方法和分子标记连锁分析被用来精细定位msc-3基因座，其被界定为具有10个注释基因的〜139.91kb区域。基因表达和结构变异分析表明，Capana10g000198编码R2R3-MYB转录因子，是msc-3基因座的最佳候选基因。表达谱分析显示Capana10g000198是花药特异性基因，Capana10g000198中163-bp的插入与雄性不育表型高度相关。此外,通过病毒诱导的基因沉默（VIGS）在雄性可育植物中下调Capana10g000198导致雄性不育。最后,msc-3基因与其他两个报道的辣椒GMS基因的可能调控关系，已经研究了msc-1和msc-2，和比较转录组分析显示，16个GMS同源物在雄性不育花药中的表达显著下调。总的来说,我们的结果表明，Capana10g000198是msc-3基因座的因果基因，为进一步深入研究辣椒花粉发育调控机制提供了重要的理论线索和依据。
