Identification, expression and potential functional analyses of the seven chloride channels in grapevine.

The study aimed at identifying and characterizing the grapevine VvCLC family, regarding its genomic organization and functional regulation, towards prospecting its putative biological functions. Using a set of bioinformatics approaches, we systematically identified seven CLCs and characterized their gene structures, phylogenetic relationship and expression profiles, as well as predicted their possible biological functions via comparative analysis with AtCLCs. RNA-seq data and in planta assays in grapevines and cultured grape cells showed that the seven VvCLC genes exhibit varietal and tissue-specific expression patterns in roots, stems, trunks, leaves and berries, suggesting transcriptional regulation of transport activity dependent on developmental stage. The analysis of the cis-elements involved in the transcriptional regulation of VvCLC genes, revealed light-responsive motifs as the most prevalent highlighting a potential role in light-mediated regulation. All VvCLC members responded to Na+ implicating their potential involvement in salt stress tolerance. Most CLCs were downregulated by water stress. The regulation of CLCs by NO3- and Cl- further suggests their involvement in the sequestration of these anions, as vacuolar nitrate/H+ antiporters and chloride channels in stomatal guard cells, supporting potential roles in cell detoxification, ionic homeostasis and photosynthesis. This study constitutes the first comprehensive characterization of the grapevine VvCLC gene family, involving seven members with distinct roles in anion transport and stress responses.