Identification and expression analysis of bHLH transcription factors family in Rhododendron delavayi

Water deficiency is a critical factor that restricts the utilization of Rhododendron delavayi in landscaping. bHLH transcription factors are pivotal regulators of plant growth, development, and stress responses. This study aimed to identify members of the R. delavayi bHLH transcription factor(RdbHLH)family by utilizing the R. delavayi genome file and transcriptome data. Through bioinformatics methods, we analyzed various aspects, including gene structure, conserved motifs, phylogenetic relationships, protein physicochemical properties, cis-acting elements, protein interaction networks, and expression patterns. The results were as follows:(1)A total of 116 RdbHLH genes were identified, exhibiting significant variations in terms of amino acid composition and molecular weight of proteins. These genes were primarily weakly acidic hydrophilic proteins that function predominantly within the cell nucleus.(2)The RdbHLH family was categorized into 17 subfamilies, where motif structures were conserved within each subfamily but displayed noticeable differences between different subfamilies. Most RdbHLH proteins contained both Motif 1 and Motif 2 at the same time. The promoter region of these genes contained a substantial number of cis-acting elements associated with plant growth and development, hormone response, light response, and stress response.(3)R. delavayi responds to drought stress by activating signal transduction pathways and regulating osmotic pressure and flavonoid biosynthesis systems, leading to stress damage mitigation. Drought stress exerted an impact on the expression of 36 RdbHLH genes, with 12 genes displaying robust induction. Notably, RdbHLH49 and RdbHLH95 might play pivotal regulatory roles in enhancing plant resistance to drought stress. These research findings provide a theoretical basis for further investigations into the biological functions of RdbHLH genes and establish target gene resources for the breeding of superior horticultural varieties of R. delavayi.