Abstract

Gibberellic acid (GA3) treatments have been previously linked to negative effects such as berry drop which can be a serious postharvest problem in terms of exportation of grapes for fresh consumption. The characterization of susceptibility to berry drop suggests that there is genotype-dependent response to GA3 treatments. For example, genotype ‘L#23’ had shown to be up to 10-fold more susceptible to berry drop than ‘Thompson Seedless’ (three seasons of evaluation). Further analysis suggest that this phenomenon could be affected by morphological changes on the pedicel as consequence of GA3, with major stiffness on treated group. RNA-sequencing on pedicel tissue was performed to characterize and identify differentially expressed genes, considering a total of 32 libraries, including: two genotypes (‘L#23’ and ‘Thompson Seedless’) and two levels of treatment (Control and GA), with four biological replicates for each group and paired-end sequencing. Differential expression analysis identified a set of 1098 and 1525 up-regulated genes by GA3 on ‘L#23’ and cv. ‘Thompson Seedless’, respectively (p-value≤0.01, FDR≤0.05, logFC≥2). Gene set enrichment analyses from such sets suggested the involvement of xylem development, flavonoids, phenylpropanoids and cell wall organization processes, among others. Validation through qPCR from a subset of selected genes on several developmental stages proved the usefulness of the transcriptomic approach in order to develop molecular tools to characterize a complex trait such as berry drop. This is the first work providing transcriptional information on pedicel tissue for V. vinifera L. table grape considering regular management conditions.