Investigation of the biostimulant activity of flavonoids on anthocyanins biosynthesis: from an explanatory approach on Gamay callus towards a future vineyard application to adapt to climate change

Abstract

Anthocyanins are key phenolic compounds in red wine, playing a major role in colour intensity and sensory quality. However, they are highly sensitive to environmental stresses such as heatwaves and droughts, which are becoming more frequent with climate change (Rienth et al., 2021). These conditions can disrupt the balance between technological and phenolic ripening in grapes, resulting in berries with excessive sugar levels but insufficient phenolic maturity at harvest. This study investigates the potential of naringenin, a key flavonoid intermediate in the anthocyanin biosynthetic pathway, and its glycoside naringin, to enhance anthocyanin accumulation and improve phenolic maturity in Vitis vinifera L. cv. Gamay cell cultures. Cellular cultures were derived from the teinturier Gamay Fréaux, a red-fleshed variant of the white-fleshed cv. Gamay, used as a simplified model to study phenolic compound biosynthesis (Afifi et al., 2004). Thirteen-day-old calli were treated with naringenin and naringin, applied individually or in combination, to reach concentrations of 1.5 mM for each compound within the tissues. Eight days after treatment, dry weight (determined after 3 days at 60°C), water content, and anthocyanin accumulation (reflected by absorbance at 535 nm) were assessed, while cell leakage rate was estimated after nine days based on absorbance at 420, 520, and 620 nm. A non-targeted transcriptomic analysis (RNA-seq) was also performed after 2 and 6 hours to explore short-term gene expression responses. The treatments had no effect on water content or callus growth, allowing a fair comparison of compound effects without any bias induced from variations in development. This also suggests an absence of toxicity, a conclusion supported by spectrophotometric data. Although individual applications of the two compounds showed no significant effect on anthocyanin levels, their combined treatment resulted in a notable 50% increase in absorbance compared to the untreated control. These promising findings could contribute to the development of sustainable vineyard strategies aimed at resynchronising technological and phenolic ripening in grapes, thereby mitigating the impact of climate change. Ongoing vineyard trials on Grenache, a variety particularly prone to producing wines with low colour intensity, are evaluating this approach using citrus peel extracts obtained through subcritical water treatment (Ko et al., 2016), which naturally contain high levels of naringenin and naringin.

References

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Rienth, M., Vigneron, N., Darriet, P., Sweetman, C., Burbidge, C., Bonghi, C., … & Castellarin, S. D. (2021). Grape berry secondary metabolites and their modulation by abiotic factors in a climate change scenario–a review. Frontiers in Plant Science, 12, 643258. https://doi.org/10.3389/fpls.2021.643258