Identification and Expression Analysis of bHLH Transcription Factor Family Members in Forsythia suspensa
The bHLH transcription factor family in Forsythia suspensa was systematically identified and characterized using genomic data, yielding 170 members with complete HLH conserved domains distributed across 14 chromosomes. Protein lengths ranged from 67 to 885 amino acids, with relative molecular masses of 7,910.58 to 98,854.78 and theoretical isoelectric points of 4.71 to 10.44. Phylogenetic analysis classified these factors into 13 subfamilies, with subfamily III being the largest. Cis-acting element analysis revealed multiple light-, hormone-, and stress-responsive elements. Exogenous methyl jasmonate (MeJA) treatment of F. suspensa leaves followed by qRT-PCR within 48 h and correlation with phillygenin content identified FsbHLH26 and FsbHLH139 as likely key regulators of phillygenin biosynthesis and accumulation. These findings provide a foundation for elucidating the molecular mechanisms underlying phillygenin biosynthesis.