Molecular Cloning, Subcellular Localization and Expression Analyses of <i>PdbHLH57</i> Transcription Factor in Colored-Leaf Poplar

bHLH transcription factors, widely exist in various plants, and are vital for the growth and development of these plants. Among them, many have been implicated in anthocyanin biosynthesis across various plants. In the present study, a PdbHLH57 gene, belonging to the bHLH IIIf group, was characterized, which was isolated and cloned from the colored-leaf poplar ‘Zhongshancaiyun’ (ZSCY). The cDNA sequence of PdbHLH57 was 1887 base pairs, and the protein encoded by PdbHLH57 had 628 amino acids, the isoelectric point and molecular weight of which were 6.26 and 69.75 kDa, respectively. Through bioinformatics analysis, PdbHLH57 has been classified into the IIIf bHLH subgroup, with many members of this subgroup known to participate in anthocyanin biosynthesis. The subcellular localization analysis conducted in the leaf protoplasts of ‘ZSCY’ revealed that the PdbHLH57 protein is specifically localized in the nucleus. The transcription activation analysis was also conducted, and the results showed that the PdbHLH57 protein had self-transcription activation. To better explore the functions of the PdbHLH57 protein, two parts of this protein (PdbHLH57-1, PdbHLH57-2) were split to detect their transcriptional activation activity. The results indicated that PdbHLH57-1 (1-433aa) had self-transcription activation, and PdbHLH57-2 (433-628aa) had no transcription activation. The expression of PdbHLH57 peaked in June during different developmental stages in ‘ZSCY’, and it was most highly expressed in the phloem among various tissues. These findings offer a basis for understanding the role of PdbHLH57 in colored-leaf poplar.