Liaoning Key Laboratory of Genetics and Breeding for Cruciferous Vegetable Crops, Department of Horticulture, Shenyang Agricultural University, 110866, Shenyang, People's Republic of China.
BMC Plant Biol. 2021 Aug 13;21(1):373. doi: 10.1186/s12870-021-03153-9.
Flowering is an important inflection point in the transformation from vegetative to reproductive growth, and premature bolting severely decreases crop yield and quality.
In this study, a stable early-bolting mutant, ebm3, was identified in an ethyl methanesulfonate (EMS)-mutagenized population of a Chinese cabbage doubled haploid (DH) line 'FT'. Compared with 'FT', ebm3 showed early bolting under natural cultivation in autumn, and curled leaves. Genetic analysis showed that the early-bolting phenotype was controlled by a single recessive nuclear gene. Modified MutMap sequencing, genotyping analyses and allelism test provide strong evidence that BrEBM3 (BraA04g017190.3 C), encoding the histone methyltransferase CURLY LEAF (CLF), was the strongly candidate gene of the emb3. A C to T base substitution in the 14th exon of BrEBM3 resulted in an amino acid change (S to F) and the early-bolting phenotype of emb3. The mutation occurred in the SET domain (Suppressor of protein-effect variegation 3-9, Enhancer-of-zeste, Trithorax), which catalyzes site- and state-specific lysine methylation in histones. Tissue-specific expression analysis showed that BrEBM3 was highly expressed in the flower and bud. Promoter activity assay confirmed that BrEBM3 promoter was active in inflorescences. Subcellular localization analysis revealed that BrEBM3 localized in the nucleus. Transcriptomic studies supported that BrEBM3 mutation might repress H3K27me3 deposition and activate expression of the AGAMOUS (AG) and AGAMOUS-like (AGL) loci, resulting in early flowering.
Our study revealed that an EMS-induced early-bolting mutant ebm3 in Chinese cabbage was caused by a nonsynonymous mutation in BraA04g017190.3 C, encoding the histone methyltransferase CLF. These results improve our knowledge of the genetic and genomic resources of bolting and flowering, and may be beneficial to the genetic improvement of Chinese cabbage.
开花是营养生长向生殖生长转变的重要转折点，而过早抽薹会严重降低作物的产量和品质。
本研究在白菜双单倍体（DH）系‘FT’的乙基甲磺酸酯（EMS）诱变群体中鉴定到一个稳定的早抽薹突变体 embm3。与‘FT’相比，embm3 在秋季自然栽培条件下表现出早抽薹和卷叶。遗传分析表明，早抽薹表型由单个隐性核基因控制。改良 MutMap 测序、基因分型分析和等位基因测试提供了强有力的证据表明，BrEBM3（BraA04g017190.3C），编码组蛋白甲基转移酶卷曲叶（CLF），是 embm3 的强候选基因。BrEBM3 的第 14 外显子中的 C 到 T 碱基替换导致氨基酸改变（S 到 F），并导致 embm3 的早抽薹表型。该突变发生在 SET 结构域（抑制蛋白效应变异性 3-9、增强子-of-zeste、Trithorax）中，该结构域催化组蛋白中特定赖氨酸的位点和状态特异性甲基化。组织特异性表达分析表明，BrEBM3 在花和芽中高度表达。启动子活性测定证实 BrEBM3 启动子在花序中具有活性。亚细胞定位分析表明，BrEBM3 定位于细胞核。转录组学研究支持 BrEBM3 突变可能抑制 H3K27me3 沉积并激活 AGAMOUS（AG）和 AGAMOUS-like（AGL）基因座的表达，导致早花。
本研究揭示了白菜 EMS 诱导的早抽薹突变体 embm3 是由 BraA04g017190.3C 中的非同义突变引起的，该基因编码组蛋白甲基转移酶 CLF。这些结果提高了我们对抽薹和开花遗传和基因组资源的认识，可能有助于白菜的遗传改良。
