Drought stress limits the growth and development of grapevines, thereby reducing productivity, but the mechanisms by which grapevines respond to drought stress remain largely uncharacterized. Here, we characterized a group A bZIP gene from “Kyoho” grapevine, VlbZIP30, which was shown to be induced by abscisic acid (ABA) and dehydration stress. Overexpression of VlbZIP30 in transgenic Arabidopsis thaliana enhanced dehydration tolerance. Transcriptome analysis revealed that a major proportion of ABA-responsive and/or drought-responsive genes are transcriptionally regulated by VlbZIP30 during ABA or mannitol treatment at the cotyledon greening stage. We identified an A. thaliana G-box motif (CACGTG) and a potential grapevine G-box motif (MCACGTGK) in the promoters of the 39 selected A. thaliana genes upregulated in the transgenic plants and in the 35 grapevine homologs, respectively. Subsequently, using two grapevine-related databases, we found that 74% (23/31) and 84% (21/25) of the detected grapevine genes were significantly upregulated by ABA and drought stress, respectively, suggesting that these genes are involved in ABA or dehydration stress and may be regulated by VlbZIP30 in grapevine. We propose that VlbZIP30 functions as a positive regulator of dehydration-responsive signaling in the ABA core signaling pathway.

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