Transcriptome analysis reveals activation of detoxification and defense mechanisms in smoke-exposed Merlot grape (Vitis vinifera) berries.

A significant consequence of climate change is the rising incidence of wildfires. When wildfires occur close to wine grape (Vitis vinifera) production areas, smoke-derived volatile phenolic compounds can be taken up by the grape berries, negatively affecting the flavor and aroma profile of the resulting wine and compromising the production value of entire vineyards. Evidence for the permeation of smoke-associated compounds into grape berries has been provided through metabolomics; however, the basis for grapevines' response to smoke at the gene expression level has not been investigated in detail. To address this knowledge gap, we employed time-course RNA sequencing to observe gene expression-level changes in grape berries in response to smoke exposure. Significant increases in gene expression (and enrichment of gene ontologies) associated with detoxification of reactive compounds, maintenance of redox homeostasis, and cell wall fortification were observed in response to smoke. These findings suggest that the accumulation of volatile phenols from smoke exposure activates mechanisms that render smoke-derived compounds less reactive while simultaneously fortifying intracellular defense mechanisms. The results of this work lend a better understanding of the molecular basis for grapevines' response to smoke and provide insight into the origins of smoke-taint-associated flavor and aroma attributes in wine produced from smoke-exposed grapes.