Transcription factor BrEFM negatively regulates flowering time in Chinese cabbage

Abstract

Flowering represents a critical developmental transition in plants. In Chinese cabbage, precise regulation of flowering time is especially vital for optimizing yield and quality. In Chinese cabbage, BrEFM and many genes annotated as flowering-related are specifically expressed in leaf veins. However, whether it regulates flowering in Chinese cabbage remains unclear. Here, we cloned BrEFM and found that it encodes a 422-residue polypeptide with a conserved Myb-DNA-binding domain in its protein sequence. Expression pattern analysis showed that BrEFM exhibits the highest expression levels in leaf veins during the rosette and heading stages, while its expression peaks in buds during early pod-setting stage. Further analysis indicated BrEFM is primarily expressed in phloem cells of leaf veins. Subcellular localization analysis demonstrated that BrEFM localizes to the nucleus. Functional analysis revealed that heterologous overexpression of BrEFM resulted in delayed bolting and flowering in transgenic Arabidopsis plants. Conversely, BrEFM-silenced Chinese cabbage plants bolted and flowered earlier than control plants. This indicates that BrEFM negatively regulates flowering in Chinese cabbage. Quantitative real-time PCR analysis suggested that BrEFM likely regulates flowering by modulating the expression of BrFT.1, BrFT.2, BrBFT, BrLFY, BrPI, and BrTSF genes. Overall, this study provides insights into elucidating the molecular mechanisms of bolting in Chinese cabbage and offers valuable gene resources for breeding bolt-resistant varieties.