Genome-wide identification of the bHLH transcription factor family in and response to low-temperature stress.

Background: Basic helix-loop-helix () transcription factors are involved in plant growth and development, secondary metabolism, and abiotic stress responses have been studied in a variety of plants. Despite their importance in plant biology, the roles and expression patterns of bHLH family genes in have not been determined.

Methods: In this study, the family genes were systematically analyzed using bioinformatics methods, and their expression patterns under low-temperature stress were analyzed by transcriptome and related physiological index measurements.

Results: In total, 142 were identified in the genome of , distributed on seven chromosomes. Phylogenetic analysis including orthologous genes in divided into 21 subfamilies, with similar structures and motifs within a subfamily. A collinearity analysis revealed seven tandem duplications and 118 segmental duplications in and 127, 150, 151, 172, and 164 segmental duplications between and , , , , and , respectively. A number of cis-regulatory elements associated with abiotic stress response and hormone response were identified in , and 21 have potential interactions with the CBF family. In addition, the expression results showed that part of bHLH may regulate the tolerance of to low-temperature stress through the jasmonic acid and pathway. Transcriptomic data showed that the expression levels of different varied during overwintering, and the expression of some was significantly correlated with relative conductivity and MDA content, implying that play important regulatory roles in response to low-temperature stress. Overall, this study provides valuable insights into the study of associated with low-temperature stress.