Natural variations of HSFA2 enhance thermotolerance in grapevine.

Heat stress limits growth and development of crops including grapevine which is a popular fruit in the world. Genetic variability in crops thermotolerance is not well understood. We identified and characterized heat stress transcription factor in heat sensitive 'Jingxiu' (named as ) and heat tolerant 'Tangwei' (named as ). The transcriptional activation activities of VdHSFA2 are higher than VvHSFA2, the variation of single amino acid (Thr315Ile) in AHA1 motif leads to the difference of transcription activities between VdHSFA2 and VvHSFA2. Based on 41 germplasms, we found that is differentiated at coding region among heat sensitive , and heat tolerant and . Genetic evidence demonstrates VdHSFA2 and VvHSFA2 are positive regulators in grape thermotolerance, and the former can confer higher thermotolerance than the latter. Moreover, VdHSFA2 can regulate more target genes than VvHSFA2. As a target gene of both VdHSFA2 and VvHSFA2, overexpression of MBF1c enhanced the grape thermotolerance whereas dysfunction of MBF1c resulted in thermosensitive phenotype. Together, our results revealed that confers higher thermotolerance than , and MBF1c acts as their target gene to induce thermotolerance. The may be adopted for molecular breeding in grape thermotolerance.