Identification and functional characterization of heat shock transcription factor genes in Rhododendron Delavayi under heat stress

Heat shock transcription factor (HSF) has been conclusively established as the most critical transcriptional regulators in plant responses to heat stress. In this study, 21 RdHSF genes were characterized in R. delavayi and their chromosomal localization, phylogenetic analysis, gene/protein structure diversity, and core promoter elements analysis were also performed. Eighteen RdHSF genes were derived from WGD/segmental and dispersed duplication events. The expression patterns of RdHSF genes in heat stress-treated R. delavayi leaves were presented. Three RdHSF genes (RdHSF7, RdHSF19, and RdHSF20) in heat stress-treated R. delavayi leaves showed over 6-fold higher expression than the control group. Among them, RdHSF20 had the most dramatic increase under heat stress. Subcellular localization revealed that the RdHSF20 protein were localized in the nucleus. Antisense oligodeoxynucleotide (AsODN) experiments showed that the AsODN interference in R. delavayi to reduce the RdHSF20 gene expression, resulting in a decrease in the expression level of RdEF1A. The dual luciferase assay further confirmed RdEF1A as a direct target of RdHSF20 gene. In addition, overexpression of RdHSF20 gene enhanced the tolerance of transgenic yeast to heat stress. This research offers valuable insights into the response of 21 RdHSFs to heat stress and screened key RdHSF20 and its target gene lays the foundation for developing R. delavayi varieties tolerant to the heat stress.