Genome-wide analysis of BrbHLH gene family and functional identification of the involvement of BcbHLH57 in abiotic stress in wucai (Brassica campestris L.)

Abstract

Wucai (Brassica campestris L. ssp. chinensis var. rosularis Tsen) is a subspecies of Brassica campestris, is a kind of cold-tolerant vegetable widely cultivated in the Yangtze-Huai River Basin of China. To breed new varieties of resistance to stress, it is necessary to study the tolerance of Resistance to different stresses. Transcriptomic data showed that exogenous application of 2, 4-epbrassinolide (EBR) significantly increased the bHLH genes expression in wucai at low temperature, and bHLH57 was up regulated significantly. BHLH (Basic helix-loop-helix) TFs (transcription factor) is a superfamily of TFs with complex functions and related to various plant life activities. In this study, a total of 239 bHLH genes were identified, and their amino acid physicochemical properties, chromosome location, gene structure, phylogeny and cis-acting elements were analyzed by bioinformatics. Phylogenetic analysis showed that bHLH gene families in Brassica rapa and Arabidopsis were divided into six groups, and the distribution of bHLH genes in Brassica rapa was uneven. The BrbHLHs were irregularly mapped in the cultivated B. rapa genome. The maximum number (40) of BrbHLH genes were mapped on Chr09. In addition, there were tandem repeats in some genes. The collinearity analysis showed that 152 AtbHLH genes and 239 BrbHLH protein genes formed 296 collinearity pairs, and the Ka/Ks ratio ofall duplicated BrbHLH gene pairs had a Ka/Ks ratio of < < 1, indicating that the bHLH family genes may have undergone strong purification and selection during the evolution process. Cis-acting elements analysis showed that the promoter region of bHLH family genes in Brassica rapa had more responsive elements related to light, hormone and abiotic stress. The BcbHLH57 overexpressing Arabidopsis thaliana lines were subjected to different stress treatments, and the seed germination rate, root growth, survival rate and various plant physiological indexes were determined. The results showed that the transgenic lines were more tolerant to salt, heat and drought stress. In this study, the response of BcbHLH57 gene to salt, heat and drought stress was reported for the first time, which provided a basis for further research on the function of BcbHLH57 in abiotic stress.