Proteomic Analysis Reveals the Molecular Pathways Responsible for Solar UV-B Acclimation in High-altitude Malbec Berries

Grapevine cultivation at high altitudes provides a viable option for producing premium quality wines in the context of climate change. This is primarily attributed to cooler temperatures, wider thermal amplitudes, and increased UV-B radiation. Although high UV-B levels can cause oxidative-stress, grape berries acclimate by generating UV-blocking anthocyanins and antioxidant compounds accumulated in the berry skins, thereby enhancing the organoleptic qualities and aging capacity of wine. This UV-B exclusion study examines how Malbec berries respond to solar UV-B at a high-altitude vineyard in Mendoza, Argentina (1350 m a.s.l.). The results showed that high solar UV-B acts both as a photomorphogenic signal and a stressor. The proteomic changes of berries exposed to +UV-B conditions indicate a decrease of photosynthesis and oxidative phosphorylation, coupled with an increase of glycolysis and tricarboxylic acid cycle as compensatory respiration pathways. Furthermore, numerous chaperones and proteins associated with the antioxidant system exhibited increased abundance to maintain cellular homeostasis. Lastly, veraison-stage berries exposed to +UV-B displayed an activation of the UVR8 signaling cascade and the phenylpropanoid pathway, resulting in higher concentration of phenolic compounds and more oxidation-resistant types of anthocyanins. This is the first report of field-grown grape berry proteomic modulation in response to solar UV-B, and it may have significant implications for the cultivation of high-quality wine grapes in both current and future climate scenarios. Significance