Field-grown Sauvignon Blanc berries react to increased exposure by controlling antioxidant homeostasis and displaying UV acclimation responses that are influenced by the level of ambient light
Abstract
Leaf removal in the bunch zone is a common viticultural practice with several objectives, yet it has been difficult to conclusively link the physiological mechanism(s) and metabolic berry impact to this widely practiced treatment. We used a field-omics approach1 in a Sauvignon blanc high altitude model vineyard, showing that the early leaf removal in the bunch zone caused quantifiable and stable responses (over years) in the microclimate where the main perturbation was increased exposure. We provide an explanation for how leaf removal leads to the shifts in grape metabolites typically linked to this treatment and confirm anecdotal evidence and previous reports that leaf removal treatment at an early stage of berry development affects “quality-associated” metabolites (monoterpenes and norisoprenoids). We show that the main physiological response occurs in the early stages of berry development when the berry is still photosynthetically active and therefore responds to changes to the microclimate in the same way as the major photosynthetically active organs (leaves). The study shows that grapevine berries respond to the increased exposure by modulating secondary metabolites with antioxidant capacity, also exhibiting clearly a degree of plasticity on the metabolic level. This lead us to propose a mechanism of antioxidant homeostasis in the different developmental stages of the berries, using unique metabolites per stage, but with similar biological functions2. A further objective was to evaluate the specific responses and/or contributions of UV exposure to the observed results. Using UV attenuation screens to modulate UV exposure and metabolite profiling of specific secondary metabolites during development and ripening we show that the berries used carotenoids and associated xanthophyll cycles to support acclimation to UV exposure and that the berry responses differed between high and low light conditions. Taken together our results support that ecologically relevant doses of UV are used by grapevine to acclimate and modulate core processes to remain productive and thriving.
1. Alexandersson et al., 2014. Frontiers in Plant Science 5:296 2. Young et al. 2016. Plant Physiology DOI:10.1104/pp.15.01775
Issue: Macrowine 2016
Type: Article
Authors
*Institute for Wine Biotechnology