Transcriptome pathways in leaf and root of grapevine genotypes with contrasting drought tolerance

Most of the world's wine-producing regions are subjected to seasonal drought, and, in the light of the dramatic climate-change events occurring in recent years, the selection of resistant rootstocks is becoming a crucial factor for the development of sustainable agricultural models to ensure optimal grape berry development and ripening. In this study, roots and leaves of 101.14 (drought-susceptible) and M4 (drought-tolerant) rootstocks were sampled in progressive drought and mRNA-seq profiles were evaluated. Physiological characterization indicated that only M4 was able to maintain high leaf transpiration and net assimilation rates under severe stress conditions. Statistical analyses, carried out on mRNA-seq data, highlighted that "treatment" (water stress) and "genotype" (rootstock-genotype) seem to be the main variables explaining differential gene expression in roots and leaves tissues, respectively. Upon water-stress, roots and leaves of the tolerant genotype M4 exhibit a higher induction of stilbenes (i.e., STS) and flavonoids (e.g., CHS, F3H, FLS) biosynthetic genes. Moreover, the higher expression of STS genes in M4 is coupled with an up-regulation of WRKYs transcription factors. STS genes promoter regions, extracted from whole genome of M4 and 101.14, highlighted a higher number of W-BOX cis elements (binding site for WRKYs) in the tolerant genotype.