Characterization of the ABA Receptor VlPYL1 That Regulates Anthocyanin Accumulation in Grape Berry Skin

Abstract

ABA plays a crucial role in controlling several ripening-associated processes in grape berries. The soluble proteins named as PYR (pyrabactin resistant)/PYL (PYR-like)/RCAR (regulatory component of ABA receptor) family have been characterized as ABA receptors. Here, the function of a grape PYL1 encoding gene involved in the response to ABA was verified through heterologous expression. The expression level of <i>VlPYL1</i> was highest in grape leaf and fruit tissues of the cultivar Kyoho, and the expression of <i>VlPYL1</i> was increased during fruit development and showed a reduction in ripe berries. Over-expression of <i>VlPYL1</i> enhances ABA sensitivity in Arabidopsis. Using the transient overexpression technique, the <i>VlPYL1</i> gene was over-expressed in grape berries. Up-regulation of the <i>VlPYL1</i> gene not only promoted anthocyanin accumulation but also induced a set of ABA-responsive gene transcripts, including <i>ABF2</i> and <i>BG3</i>. Although tobacco rattle virus (TRV)-induced gene silencing (VIGS) was not successfully applied in the "Kyoho" grape, the application of the transient overexpression technique in grape fruit could be used as a novel tool for studying grape fruit development.