PbTCP2–PbTCP4 protein complex promotes pear flowering by suppressing transcription of the flowering-inhibition gene PbSVP

Both PbTCP2 and PbTCP4 regulate the flowering of pears. PbTCP2 blocks transcription of the flowering-inhibition gene PbSVP ( SHORT VEGETATIVE PHASE ) by directly interacting with its promoter. Transcriptional repression of PbSVP is enhanced when PbTCP2 forms a complex with PbTCP4. Members of the TEOSINTE BRANCHED 1/CYCLOIDEA/PROLIFERATING CELL FACTOR (TCP) family are plant-specific transcription factors regulating numerous growth and developmental processes, including the flowering transition. However, the roles of TCP genes in regulating the flowering of pear remain unknown. Here, we identified PbTCP2 as a transcription factor associated with flowering. PbTCP2 was identified as a typical nucleus-located transcription factor without self-activation activity. The biofunction of PbTCP2 in promoting flowering was verified by heterologously expressing it in Arabidopsis . Compared with wild-type lines, the transcription levels of flowering activators in PbTCP2 -overexpressing Arabidopsis were increased, while the transcription levels of flowering repressors, including PbSVP ( SHORT VEGETATIVE PHASE ), were significantly decreased. Yeast one-hybrid and electrophoretic mobility shift assays indicated that TCP2 protein directly binds to the promoter of PbSVP . The transcriptional repression activity of PbTCP2 on PbSVP was further confirmed by dual-luciferase assays. We further show that PbTCP4 interacts with PbTCP2, as evidenced by yeast two-hybrid, bimolecular fluorescence complementation, and pull-down assays. Notably, forming a complex with PbTCP2, PbTCP4 synergistically enhances this repression, a conclusion supported by dual-luciferase and GUS staining assays. Overexpression of PbTCP4 also promoted flowering in Arabidopsis . Collectively, these findings confirm a PbSVP -controlled flowering mechanism regulated by the TCP4–TCP2 complex in pear, shedding light on the molecular mechanisms underlying flowering regulation in perennial crops.