Abstract

The primary domain/leucine zipper (bZIP) transcription factor, Elongated Hypocotyl (HY5), is crucial for the photomorphogenesis of seedlings. Here, we identifiedBcHY5as a regulator of hypocotyl length from the non-heading Chinese cabbage (NHCC) variety ‘Suzhouqing’, which encoded a protein comprised 164 amino acid residues. Ectopic expression ofBcHY5inArabidopsisshortens the length of the hypocotyl. Additionally, we discovered a protein called BcBBX24 containing the B-BOX (BBX) domain, which is the interacting partner of BcHY5. Yeast two-hybrid (Y2H), bimolecular fluorescence complementation (BiFC) and GST pull-down assays revealed that BcHY5 interacted with BcBBX24. Additionally, by physically binding to the promoter ofBcHY5, BcBBX24 inhibited the transcriptional activity of BcHY5. Therefore, our findings reveal a transcriptional mechanism through which light response occurs in NHCC seedlings, where BcHY5 can interact with BcBBX24 and BcBBX24 can preventBcHY5transcription.Keywords:non-heading Chinese cabbage;BcHY5;photomorphogenesis;hypocotyl;BcBBX24