Identification of HsfB Family in Peanut (Arachis hypogea) and Role of AhHsfB1-5A in High-Temperature Stress

Global warming-triggered heat stress severely restricts plant growth and crop productivity. Peanut (Arachis hypogaea L.), a vital oilseed and cash crop that is susceptible to high temperatures throughout its growth cycle, exhibits inhibited peg and pod development, growth retardation, and premature leaf senescence under heat stress, which ultimately causes substantial yield losses. Heat shock factors (Hsfs) serve as core regulatory modulators of plant abiotic stress tolerance, among which the HsfB subfamily exerts a critical function in thermotolerance modulation. Nevertheless, the biological functions of peanut HsfB genes remain largely uncharacterized. In the present study, a total of 16 HsfB subfamily members were identified from the peanut genome, possessing highly conserved gene structures and protein motifs. Phylogenetic analysis revealed that the peanut AhHsfB genes are classified into four distinct subfamilies. Chromosomal localization analysis indicated that these 16 AhHsfB genes are unevenly distributed across nine peanut chromosomes. Transcriptomic profiling demonstrated that the transcript levels of AhHsfB genes were significantly upregulated by 6- to 120-fold upon heat stress exposure. Subcellular localization and transcriptional activity assays further validated that AhHsfB1-5A is a nucleus-localized protein with intrinsic transcriptional activation activity. Ectopic overexpression of AhHsfB1-5A in Arabidopsis thaliana remarkably enhanced seed germination ability and antioxidant capacity under heat stress conditions, with a maximum 18.84% increase in green seedling rate. This study systematically characterizes the HsfB subfamily in peanut and elucidates the positive regulatory role of AhHsfB1-5A in plant thermotolerance. These findings deepen our understanding of the role of HsfB and provide valuable genetic resources for molecular breeding of heat-resistant peanut varieties.