Characterization and Functional Analysis of FaHsfC1b from Festuca arundinacea Conferring Heat Tolerance in Arabidopsis

Abstract

Heat transcription factors (<i>Hsfs</i>) belong to a large gene family classified into A, B, and C groups, with classes A and B <i>Hsfs</i> being well-characterized and known for their roles in plant tolerance to abiotic stresses. The functions and roles of Class C <i>Hsfs</i> are not well-documented. The objectives of this study were to characterize a class C <i>Hsf</i> gene (<i>FaHsfC1b</i>) cloned from tall fescue (<i>Festuca arundinacea</i>), a perennial grass species, and to determine the physiological functions of <i>FaHsfC1b</i> in regulating heat tolerance by overexpressing <i>FaHsfC1b</i> in <i>Arabidopsis thaliana</i>. Full length cDNA of <i>FaHsfC1b</i> was cloned and the sequence alignment showed that it had high similarity to <i>OsHsfC1b</i> with typical DNA binding domain, hydrophobic oligomerization domain, and a nucleus localization signal. Transient expression with <i>FaHsfC1b</i>-eGFP in protoplasts of Arabidopsis leaves indicated its nucleus localization. qRT-PCR analysis showed that <i>FaHsfC1b</i> responded to heat, osmotic, salt, and cold stress in leaves and roots during 48-h treatment. Physiological analysis showed that <i>FaHsfC1b</i> overexpression enhanced plant survival rate, chlorophyll content, and photochemical efficiency, while it resulted in decreases in electrolyte leakage, H₂O₂ and O^2- content under heat stress. qRT-PCR showed that endogenous <i>HsfC1</i> was induced in transgenic plants and the expression levels of heat protection protein genes, including several <i>HSPs</i>, <i>AtGalSyn1</i>, <i>AtRof1</i>, and <i>AtHSA32</i>, as well as ABA-synthesizing gene (<i>NCED3</i>) were significantly upregulated in transgenic plants overexpressing <i>FaHsfC1b</i> under heat stress. Our results first demonstrate that <i>HsfC1b</i> plays positive roles in plant tolerance to heat stress in association with the induction and upregulation of heat-protective genes. <i>HsfC1b</i> may be used as a candidate gene for genetic modification of cool-season plant species for improving heat tolerance.