Flower development is essential for the sexual reproduction and crop yield of plants. Thus, a better understanding of plant sterility from the perspective of morphological and molecular genetics is imperative. In our previous study, a recessive female-sterile Chinese cabbage mutant fsm was obtained from a doubled haploid line ‘FT’ via an isolated microspore culture combined with EMS mutagenesis. Pistil aniline blue staining and stigma scanning observation showed that the growth of the stigma papillar cells and pollen tubes of the mutant fsm were normal. Therefore, the female sterility was due to abnormal development of the ovules. To map the mutant fsm, 3108 F₂ individuals were selected for linkage analysis. Two closely linked markers, Indel-I2 and Indel-I7, were localized on the flanking region of fsm at distances of 0.05 cM and 0.06 cM, respectively. The physical distance between Indel-I2 and Indel-I7 was ~ 1376 kb, with 107 genes remaining in the target region. This region was located on the chromosome A04 centromere, on which low recombination rates and a high frequency of repetitive sequences were present. Whole-genome re-sequencing detected a single-nucleotide (C-to-A) transition (TCG/TAG) on the exon of BraA04001030, resulting in a premature stop codon. Genotyping revealed that the female-sterile phenotype was fully cosegregated with this SNP. BraA04001030 encodes a homologue of STERILE APETALA (SAP) transcriptional regulator, which plays vital roles in floral development. The results of the present study suggest that BraA04001030 is a strong candidate gene for fsm and provide the basis for exploring the molecular mechanism underlying female sterility in Chinese cabbage.

中文翻译：

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雄蕊不育的错义突变导致白菜（Brassica campestris ssp。pekinensis）中的女性不育。

花卉发育对于植物的有性繁殖和农作物产量至关重要。因此，必须从形态学和分子遗传学的角度更好地了解植物的不育性。在我们之前的研究中，通过分离的小孢子培养物结合EMS诱变，从双倍单倍体系'FT'获得了隐性的女性不育大白菜突变体fsm。雌蕊苯胺蓝染色和柱头扫描观察表明，fsm突变体柱头乳头细胞和花粉管的生长正常。因此，女性不育是由于胚珠异常发育所致。要映射突变体fsm，3108 F ₂选择个体进行连锁分析。两个紧密相连的标记，Indel-I2和Indel-I7，分别位于fsm的侧翼区域，距离分别为0.05 cM和0.06 cM。Indel-I2和Indel-I7之间的物理距离为〜1376 kb，其中107个基因保留在目标区域中。该区域位于染色体A04着丝粒上，在该染色体上存在低重组率和高频率的重复序列。全基因组重新测序在BraA04001030的外显子上检测到单核苷酸（C到A）过渡（TCG / TAG），导致终止密码子过早。基因分型显示，女性不育表型与该SNP完全共隔离。BraA04001030编码的同系物无菌APETALA （SAP）转录调节因子，在花卉发育中起着至关重要的作用。本研究结果表明，BraA04001030是fsm的强候选基因，并为探索大白菜女性不育的分子机制提供了基础。