test. Transcriptomics of the grape berry shrivel ripening disorder

The lower expression at veraison of several ripening master regulators “switch genes” can play a centralrole in the induction of the berry shrivel ripening physiological disorder in grapevine.Abstract Berry shrivel (BS) is a ripening physiological disorder affecting grape berry with visible symptoms appearing afterveraison. Berry shrivel leads to shrinking berries with a reduced weight and a lower content of sugars and anthocyanins.In this study, for the first time a transcriptomic analysis coupled with selected metabolites quantification was undertakento understand the metabolic modifications induced by the disorder. Different stages of berry development were consideredincluding pre- and symptomatic berries. No metabolic alterations in the berry transcriptome and in the metabolite content wasobserved in pre-symptomatic and pre-veraison samples. Interestingly, at veraison, with still not visible symptoms appearingon the berry, a subset of genes, called switch genes previously suggested as master regulators of the ripening onset in grapeberries, were strongly lower expressed in BS. Later during the ripening phase and with visible symptoms of the disorder,more than 3000 genes were differentially expressed. The genes up-regulated were related to hormone biosynthesis, responseto stress and the phenylpropanoid pathway, while the genes down-regulated during ripening belonged mainly to the flavonoidpathway, and the sugar metabolism. In agreement, BS berries showed lower content of sugars and anthocyanins from theonset of veraison onward, while the amount of acids was not significantly affected. In conclusion, these results highlight apivotal role of the switch genes in grapevine ripening, as well as their possible contribution to induce the ripening disorderberry shrivel, although it remains unclear whether this is part of the cause or consequences of the BS disorder.