Genome-Wide Identification of HSF Gene Family in Kiwifruit and the Function of AeHSFA2b in Salt Tolerance

Abstract

Heat shock transcription factors (<i>HSFs</i>) play a crucial role in regulating plant growth and response to various abiotic stresses. In this study, we conducted a comprehensive analysis of the <i>AeHSF</i> gene family at genome-wide level in kiwifruit (<i>Actinidia eriantha</i>), focusing on their functions in the response to abiotic stresses. A total of 41 <i>AeHSF</i> genes were identified and categorized into three primary groups, namely, HSFA, HSFB, and HSFC. Further transcriptome analysis revealed that the expression of <i>AeHSFA2b/2c</i> and <i>AeHSFB1c/1d/2c/3b</i> was strongly induced by salt, which was confirmed by qRT-PCR assays. The overexpression of <i>AeHSFA2b</i> in Arabidopsis significantly improved the tolerance to salt stress by increasing <i>AtRS5</i>, <i>AtGolS1</i> and <i>AtGolS2</i> expression. Furthermore, yeast one-hybrid, dual-luciferase, and electrophoretic mobility shift assays demonstrated that <i>AeHSFA2b</i> could bind to the <i>AeRFS4</i> promoter directly. Therefore, we speculated that <i>AeHSFA2b</i> may activate <i>AeRFS4</i> expression by directly binding its promoter to enhance the kiwifruit's tolerance to salt stress. These results will provide a new insight into the evolutionary and functional mechanisms of <i>AeHSF</i> genes in kiwifruit.