Genome-wide analysis of basic helix−loop−helix family transcription factors and their role in responses to abiotic stress in carrot

Environmental stresses significantly influence the growth and development of plants. To overcome these stresses, higher plants have evolved a variety of complicated molecular mechanisms. Basic helix−loop−helix (bHLH) transcription factors (TFs) play important roles in plant growth and development in response to environmental stresses. Here, a total of 146 DcbHLH TFs were identified from carrot, based on a genomic and transcriptomic database. Based on the previous classification system of Arabidopsis thaliana, the DcbHLH TFs were divided into 17 subfamilies. Multiple sequence alignment of bHLH conserved domains indicated that 109 DcbHLH proteins were bound to DNA (83 proteins were E-box binders and 52 DcbHLHs were G-box binders). From evolutionary analysis, bHLH TFs selected from plants, metazoans, and fungi demonstrated that the number of bHLH TFs increased during the evolution of these species. The expression profiles of eight DcbHLH genes from subfamily 15 showed differences in three tissues and four abiotic stresses in two carrot cultivars, Junchuanhong and Kurodagosun. This study presented useful information on the structure and function of DcbHLH factors in the regulatory mechanisms of carrot.