Characterization of thermotolerance-related genes in grapevine (Vitis vinifera)

We report the cloning and characterization of heat shock-induced genes in grapevine (Vitis vinifera L.). Using the cDNA subtraction method, four heat shock-induced genes were identified in heat shock-treated Pinot noir grapevine. The four genes were immediately induced and upregulated in leaves and berry skins by heat treatment at 45 degrees C. The recovery treatment at 26 degrees C reduced the upregulated transcription of the heat shock-induced genes to near basal levels. The predicted amino acid sequences of three genes, HSG4, HSG14, and HSG19, showed high homologies to those of known small heat shock proteins of other plants. The predicted amino acid sequence of the fourth gene, HSG1, has two conserved motifs, the IQ motif and the Bcl-2-associated athanogene (BAG) domain, suggesting that HSG1 may be a member of the BAG family in grapevine. Although no morphological changes were observed, the overexpression Arabidopsis lines of HSG1, HSG4, HSG14, or HSG19 exhibited faster growth including floral transition than the control line, suggesting that the constitutive expression of HSG1, HSG4, HSG14, or HSG19 protein resulted in increased growth rates without any detectable harm. The thermotolerance test demonstrated that all of the overexpression lines remained viable and noticeably healthy compared with the control line even after exposure to severe heat shock, suggesting that HSG1, HSG4, HSG14, or HSG19 protein might be related to the acquisition of thermotolerance in grapevine.