Identification of bHLH transcription factors in moso bamboo (Phyllostachys edulis) and their expression analysis under drought and salt stress

The transcription factors of the bHLH family have important regulatory effects on plant growth and development. Here, Phyllostachys edulis (Carr.) Lehaie was used as experimental material to understand the characteristics of bHLH family members in bamboo and explore their expression patterns under adverse conditions. Bioinformatics were used to identify and systematically analyze the bHLH family members at the genomic level, and their expression patterns in different tissues and expression of several bHLH genes under high salt and drought stress conditions were further analyzed. Our results identified 153 bHLH transcription factor genes (PebHLH001-PebHLH153) with complete conserved domains in Ph. edulis. The number of introns in PebHLHs ranged from 0 to 14. The drought and salt stress related cis-acting elements were found in the promoters of 137 PebHLHs. The length of the proteins encoded by PebHLHs ranged from 134 aa (PebHLH005) to 1401 aa (PebHLH083) with molecular weights of 13.4 to 152.6 kD, respectively. Based on phylogenetic analysis of bHLHs in Ph. edulis and Oryza sativa L., 153 PebHLHs were clustered into 17 subgroups, with the C subgroup containing the highest number (42). According to expression profile analysis of transcriptome data, 151 PebHLHs exhibited different expression levels in different tissues and growth stages of Ph. edulis. Real-time quantitative polymerase chain reaction (PCR) showed that 14 PebHLHs were up-regulated and two PebHLHs were down-regulated after drought stress, whereas 13 were up-regulated and three were down-regulated after salt stress. However, there were some differences in the expression patterns of 16 PebHLHs, indicating that they may play different roles in response to drought and salt stress.