Abstract: 【Objective】 To investigate the characteristics and functions of the bHLH gene family of Platycodon grandiflorus. 【Methods】 Analyses of physicochemical properties,phylogenetic tree,conserved motifs,gene structures,cis-regulatory elements,and collinearity analysis were conducted for the bHLH gene family of P. grandiflorus. Quantitative real-time PCR （qRT-PCR） was used to examine the expression patterns of bHLH genes in tissues of P. grandiflorus. 【Results】 A total of 94 members were identified in the bHLH gene family of P. grandiflorus,which were classified into nine subfamilies and distributed across eight chromosomes. Conserved motif analysis showed that Motif1 and Motif2 were the major conserved motifs of this family. The gene structures were diverse,containing 1-11 exons. Analysis of cis-regulatory elements in the promoters revealed that they contained response elements associated with light responsiveness,plant hormones,and stress. Collinearity analysis identified 18 pairs of duplicated bHLH genes. Tissue-specific expression analysis indicated that PgbHLH65,PgbHLH8,and PgbHLH72 were higher relative expression in stems,PgbHLH82 and PgbHLH20 showed higher relative expression in roots,and PgbHLH10,PgbHLH52,and PgbHLH91 exhibited higher relative expression in leaves. 【Conclusion】 Different bHLH genes may perform specific functions in the roots,stems,and leaves of P. grandiflorus.

Key words: Platycodon grandiflorus, bHLH gene, Transcription factor, Bioinformatics, Tissue expression pattern