Histone deacetylase BrHDA19 is involved in regulating bolting time in Chinese cabbage.

key messageThe role of BrHDA19 in regulating bolting time was firstly reported in Chinese cabbage and confirmed by heterologous transformation in Arabidopsis. Bolting represents a critical agronomic trait in Chinese cabbage, and deciphering the molecular regulatory network governing bolting, as well as identifying key genes that regulate bolting time, are essential for production and breeding programs in Chinese cabbage. In this study, a genetically stable early-bolting mutant, designated ebm0767, was generated via EMS mutagenesis using a DH line 'FT' of Chinese cabbage. Through a combination of MutMap and KASP-based linkage analysis, BraA01g044250.3.5C was identified as the most probable candidate gene. BraA01g044250.3.5C exhibits high sequence homology with the Arabidopsis AT4G38130 gene and encodes a histone deacetylase HDA19; accordingly, it was named BrHDA19. Gene cloning revealed that the mutant harbors a C-to-T mutation within the first exon of BrHDA19, resulting in the formation of a premature termination codon. Expression profiling indicated that BrHDA19 was expressed in various tissues, with significantly reduced transcript levels in the mutant compared to the wild-type 'FT'. Subcellular localization confirmed that BrHDA19 localized to the nucleus. To validate the role of BrHDA19 in regulating bolting time, heterologous transformation experiments in Arabidopsis demonstrated that the mutation in BrHDA19 was the primary cause for the early-bolting phenotype of mutant ebm0767. Notably, the expression levels of the flowering-promoting genes FT and SOC1 were markedly elevated in the mutant relative to the wild-type 'FT'. This study presents the first evidence implicating BrHDA19 in the regulation of bolting time in Chinese cabbage, thereby establishing a crucial foundation for further elucidation of the molecular mechanisms through which BrHDA19 modulates the transition from vegetative to reproductive growth.