GSE67932
Developmental and metabolic plasticity of ripe Sémillon grape berries in response to Botrytis cinerea during noble rot
Noble rot results from atypical infections of ripe grape berries by Botrytis cinerea. Unlike bunch rot, noble rot promotes favorable changes in grape berries and accumulation of secondary metabolites that enhance wine grape quality. Noble rot-infected berries of Sémillon, a white-skinned variety, were collected over three years from a commercial vineyard at the same time fruit were harvested for botrytized wine production. Transcriptomic and metabolomic data were integrated to identify pathways associated with distinct stages of noble rot. Botrytis induced the expression of known key regulators of pathways in secondary metabolism associated with berry ripening. The activation by Botrytis during noble rot of metabolic pathways associated with berry ripening was further supported by comparisons with transcriptomes of red-skinned varieties at véraison. A prominent and common outcome of noble rot and berry ripening was the enhancement of the phenylpropanoid metabolism. Induced synthesis of stilbenes, flavonoids, and anthocyanins was supported by both transcriptional and metabolite analyses. Enzyme assays and targeted gene expression analyses of samples from the three distinct years confirmed that the activation of central and peripheral phenylpropanoid pathways is a consistent hallmark of noble rot. Finally, we show that the impact of noble rot on grape metabolism is still detectable in botrytized wines. These results demonstrate that despite the late stage of terminal senescence of a plant organ, a biotic stress can cause a major reprogramming of plant metabolism leading, in case of noble rot, to the synthesis of important metabolites for grape berry flavor and aroma. Overall design: The experimental design consists of 4 treatments, berries at 3 distinct stages of noble rot and berries without apparent symptoms of infection. From each treatment a total of 4 biological replicates were sequenced with RNAseq, each replicate corresponded to independent pools of 10-15 berries harvested from adjacent grapevines.