2026-08-20
Smoke from wildfires and other events can change the chemistry of wine grapes in ways that later show up in aroma and flavor, and new research indexed on PubMed offers a closer look at the genes that may drive that process inside the berry.
The study focused on smoke taint, a long-running problem for grape growers and winemakers in regions exposed to fire smoke. Researchers said smoke contamination can alter grape and wine composition and damage sensory quality. A central part of that process is the buildup in smoke-exposed grapes of glycoconjugates linked to volatile phenols, compounds associated with smoky, ashy and medicinal notes in finished wine.
To examine what happens at the molecular level, the researchers used RNA sequencing to measure the activity of genes that encode glycosyltransferases in berries from two Vitis vinifera cultivars, Shiraz and Cabernet Sauvignon, after smoke exposure. Glycosyltransferases are enzymes that attach sugar molecules to other compounds. In grapes exposed to smoke, that matters because sugar binding can change how smoke-derived compounds are stored in the fruit and how they later affect wine.
The work also drew on publicly available microarray datasets to look for UDP-glycosyltransferases, or UGTs, that become more active in fruit under stress. That broader analysis found several UGTs with higher transcript levels after either biotic or abiotic stress, suggesting that some of the same enzyme families involved in general stress responses may also play a part when grapes are exposed to smoke.
The RNA-sequencing results then narrowed that picture. According to the study, specific UGT transcripts were upregulated in grape berries after smoke exposure, and the response was not identical across the two cultivars. That difference is important because it points to the possibility that grape varieties do not process smoke compounds in the same way. In practical terms, some cultivars may be more likely than others to accumulate the bound forms of volatile phenols that are associated with later quality problems in wine.
The researchers identified several candidate UGT genes whose increased expression may be linked to the glycosylation of smoke-derived volatile phenols. The study stops short of saying those genes alone explain smoke taint, but it places them among the strongest molecular leads yet for understanding how the problem develops in the fruit before grapes ever reach the winery.
That distinction matters for the beverage sector because smoke taint is not only a vineyard issue. It can cut the value of a harvest, complicate grape purchasing decisions, and force wineries to spend more on testing, blending or remediation. In years with major fires, uncertainty over whether grapes will produce clean wines can affect contracts, insurance disputes and the release schedules of finished bottles. If researchers can pinpoint the genes involved in storing smoke compounds, growers and producers may eventually gain better tools to assess risk earlier and protect wine quality more reliably.
The study also adds detail to a question that has become more urgent as fire seasons have grown longer and more destructive in many wine regions. Smoke exposure does not always produce obvious damage in the vineyard, and fruit can appear sound at harvest while still carrying compounds that create problems during fermentation or aging. By showing that grape berries switch on particular glycosyltransferase-related transcripts after exposure, the researchers provide a molecular signal that could, over time, help support more precise screening methods.
For grape breeders, the findings may also help identify cultivars or clones with different smoke-response profiles. For winemakers, the work could inform future decisions about whether to harvest, separate lots, or apply mitigation strategies when smoke exposure occurs near ripening. For laboratories and technology developers, the candidate genes offer a narrower set of targets for follow-up testing.
The researchers said their results highlight the transcriptional regulation of UGT genes as a likely factor in the formation of the glycoconjugates associated with smoke taint. They added that understanding these mechanisms could support the development of strategies to mitigate smoke taint in grapes and improve wine quality after wildfires or other smoke events.
Even so, the study describes a step in the research process rather than a finished solution. The candidate genes still need further validation to confirm exactly which enzymes act on smoke-derived volatile phenols and how those reactions vary across cultivars, vineyard conditions and stages of ripening. But by moving the discussion from broad observations of smoke damage to specific transcriptional responses in grape berries, the research gives the wine industry a clearer biological map of a problem that has become harder to ignore.