Huang Shengnan, Hou Li, Fu Wei, Liu Zhiyong, Li Chengyu, Li Xiang, Feng Hui
Department of Horticulture, Shenyang Agricultural University, Shenyang, China.
Front Plant Sci. 2020 May 12;11:547. doi: 10.3389/fpls.2020.00547. eCollection 2020.
Bolting is an important agronomic character of the Chinese cabbage, but premature bolting can greatly reduce its commercial value, yield, and quality. Here, early-bolting mutant 1 () was obtained from a Chinese cabbage doubled haploid (DH) line "FT," by using an isolated microspore culture and ethyl methanesulfonate (EMS) mutagenesis. The was found to bolt extremely earlier than the wild type "FT." Genetic analysis indicated that the phenotype of the was controlled by a single recessive nuclear gene. Using a mapping population of 1,502 recessive homozygous F individuals with the phenotype, the gene was mapped to between the markers SSRhl-53 and SSRhl-61 on chromosome A04 by using SSR markers, and its physical distance was 73.4 kb. Seven genes were predicted in the target region and then cloned and sequenced; the only difference in the sequences of the and "FT" genes was with . Unlike that in "FT," the in had a novel 53 bp insertion that caused the termination of amino acid coding. The mutation was not consistent with EMS mutagenesis, and thus, may have been caused by spontaneous mutations during the microspore culture. Based on the gene annotation information, was found to encode the histone methyltransferase () in . regulates the expression of flowering-related genes. Further genotyping revealed that the early-bolting phenotype was fully co-segregated with the insertion mutation, suggesting that was the most likely candidate gene for . No significant differences were noted in the expression levels between the and "FT." However, the expression levels of the flowering-related genes , , , and were significantly higher in the than in the "FT." Thus, the mutation of is responsible for the early-bolting trait in Chinese cabbage. These results provide foundation information to help understand the molecular mechanisms of bolting in the Chinese cabbage.
抽薹是大白菜的一个重要农艺性状，但过早抽薹会大大降低其商业价值、产量和品质。在此，通过小孢子离体培养和甲基磺酸乙酯（EMS）诱变，从大白菜双单倍体（DH）系“FT”中获得了早抽薹突变体1（）。发现该突变体比野生型“FT”抽薹早得多。遗传分析表明，该突变体的表型受单个隐性核基因控制。利用1502个具有该突变体表型的隐性纯合F个体组成的定位群体，通过SSR标记将该基因定位到A04染色体上的SSRhl - 53和SSRhl - 61标记之间，其物理距离为73.4 kb。在目标区域预测了7个基因，然后进行克隆和测序；该突变体与“FT”基因序列的唯一差异在于。与“FT”不同，该突变体中的有一个新的53 bp插入，导致氨基酸编码终止。该突变与EMS诱变不一致，因此可能是小孢子培养过程中的自发突变所致。根据基因注释信息，发现该突变体中的编码组蛋白甲基转移酶（）。调节开花相关基因的表达。进一步的基因分型显示，早抽薹表型与插入突变完全共分离，表明最有可能是该突变体基因的候选基因。该突变体与“FT”之间的表达水平没有显著差异。然而，开花相关基因、、和在该突变体中的表达水平显著高于“FT”。因此，的突变是大白菜早抽薹性状的原因。这些结果为理解大白菜抽薹的分子机制提供了基础信息。
