Identification of the MADS-Box Gene Family and the Key Role of BrAGL27 in the Regulation of Flowering in Chinese Cabbage (Brassica rapa L. ssp. pekinensis)

Chinese cabbage (<i>Brassica rapa</i> L. ssp. <i>pekinensis</i>) is a key vegetable crop in Asia, but its commercial value is often reduced by premature flowering triggered by vernalization. The molecular mechanisms behind this process are not fully understood. MADS-box genes, as crucial transcriptional regulators, play vital roles in plant development, including flowering. In this study, 102 MADS-box genes were identified in Chinese cabbage through bioinformatics analyses, covering phylogeny, chromosomal localization, and gene structure. Real-time quantitative PCR and RNA-seq data analysis revealed that the expression level of AGL27 declined as vernalization time increased. To determine <i>BrAGL27</i>'s functions, we obtained BrAGL27-overexpressed (OE) <i>Arabidopsis thaliana</i> lines that showed significantly later flowering compared with the wild type (WT). The expression levels of flowering suppressor genes <i>AtFLC</i> and <i>AtTEM1</i> were significantly high-regulated in the BrAGL27-OE lines compared to WT plants, while the expression levels of the floral genes <i>AtSPL15</i>, <i>AtSOC1</i>, <i>AtFT</i>, and <i>AtAP3</i> were significantly lower in the BrAGL27-overexpressed lines than in the wild type. These findings enhance understanding of MADS-box genes in vernalization and flowering regulation, offering a basis for further research on bolting resistance and flowering control in Chinese cabbage.