Genome-Wide Identification of bHLH Transcription Factor Family in and Functional Exploration of Gene under Canker Infection.

Xinjiang wild apple () is an ancient relic; a plant with abundant genetic diversity and disease resistance. Several transcription factors were studied in response to different biotic and abiotic stresses on the wild apple. Basic/helix-loop-helix (bHLH) is a large plant transcription factor family that plays important roles in plant responses to various biotic and abiotic stresses and has been extensively studied in several plants. However, no study has yet been conducted on the bHLH gene in . Based on the genome of , 184 putative genes were identified, and their physicochemical properties were studied. covered 23 subfamilies and lacked two subfamily genes of based on the widely used classification method. Moreover, exon-intron structures matched subfamily classification, as evidenced by the analysis of their protein motifs. The analysis of cis-acting elements revealed that many genes share stress- and hormone-related cis-regulatory elements. These MsbHLH transcription factors were found to be involved in plant defense responses based on the protein-protein interactions among the differentially expressed . Furthermore, 94 genes were differentially expressed in response to pathogenic bacteria. The qRT-PCR results also showed differential expression of genes. To further verify the gene function of bHLH, our study used the transient transformation method to obtain the overexpressed transgenic plants and inoculated them. Under canker infection, the lesion phenotype and physiological and biochemical indexes indicated that the antioxidant capacity of plants could increase and reduce the damage caused by membrane peroxidation. This study provides detailed insights into the classification, gene structure, motifs, chromosome distribution, and gene expression of genes in and lays a foundation for a better understanding disease resistance in plants, as well as providing candidate genes for the development of resistance breeding.