Abstract
BackgroundFlowering is an important inflection point in the transformation from vegetative to reproductive growth, and premature bolting severely decreases crop yield and quality.ResultsIn 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.ConclusionsOur 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.
Highlights
Flowering is an important inflection point in the transformation from vegetative to reproductive growth, and premature bolting severely decreases crop yield and quality
FLOWERING T (FT) is produced in the leaves and is transported via the phloem to the shoot apical meristem (SAM), where it interacts with FLOWERING LOCUS D (FD) to induce SOC1 and the floral meristem identify genes APETALA 1 (AP1) and CAULIFLOWER (CAL) [7]
By continuous identification and further screening for generations, the mutant ebm3 exhibiting obvious earlybolting characteristics in spring and autumn cultivation was selected as the study material
Summary
Flowering is an important inflection point in the transformation from vegetative to reproductive growth, and premature bolting severely decreases crop yield and quality. The timing of floral induction is determined by the interaction of environmental and endogenous cues, ensuring that flowering occurs under the conditions the most likely to maximize offspring quantity and quality [1, 2]. One goal of plant breeding is to improve plant adaptability to climate changes and new environment by controlling flowering time, to increase crop yield and quality. In A.thaliana, six major genetic pathways controlling flowering time, i.e., photperiod, vernalization, autonomous, gibberellin, ambient temperature, and age, have been described [4]. Flowering is one of the most complex regulated pathways, the signaling cross-talk between the pathways induced flowering is ubiquitous Such as cross-talk between vernalization and photperiod pathways ensures that plants adapt more effectively during unpredictable environmental condidtions [5]. FT is produced in the leaves and is transported via the phloem to the shoot apical meristem (SAM), where it interacts with FLOWERING LOCUS D (FD) to induce SOC1 and the floral meristem identify genes APETALA 1 (AP1) and CAULIFLOWER (CAL) [7]
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