Combined omics data reveal multilevel response to water deficit in grapevine disease-resistant varieties

Climate change is intensifying drought stress in viticultural regions, threatening grapevine productivity and quality. New genotypes previously bred for disease resistance are an untested resource regarding their water deficit tolerance. Field experiments were conducted over two seasons, applying well-watered and water-stress treatments in two disease-resistant varieties, Fleurtai and Cabernet Volos. Physiological measurements, RNA sequencing, and GC-MS-based metabolite profiling of leaves were integrated, correlating gene expression and metabolite accumulation with stem water potential (Ψ_S) using a factorial analyses design by FaDSeqSes script. We identified three categories of response: (1) genes and metabolites similarly regulated by water deficit in both genotypes, belonging to several different pathways (such as carbohydrate metabolism, amino acid metabolism, secondary metabolism, and hormone metabolism), among which sugar metabolism was one of the most striking ones, including changes in accumulation of raffinose and galactinol, and induction of genes coding for their synthesis; (2) responses specific to Cabernet Volos, characterized by downregulation of kinase and receptor genes likely to be involved in shutting down biotic defense response; and (3) responses specific to Fleurtai, including accumulation of caffeoylquinate and upregulation of genes involved terpene synthesis and in ABA regulation. We found that each genotype has an individual way to combat water deficits; Cabernet Volos accumulates more osmoprotectant compounds at a constant and higher level, while Fleurtai synthesizes these compounds as needed when stress occurs. This study underscores overall grapevine responses to water deficits, as well as the contribution of the genotype.