Identification and Functional Characterization of Genes Involved in Abscisic Acid and Brassinosteroid Catabolism in Grapevine

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Grapevine berries are commercially cultivated primarily for value added products such as wines in Canada. Wine grapes are produced mainly in Ontario and British Columbia, as well as Quebec and Nova Scotia. As well as being an economically important food product, pigmented ('red') grapes are rich in antioxidant compounds which have numerous reported human health benefits. Fruit physiologists classify ripening into two categories, climacteric and non-climacteric. A small number of agriculturally important fruits are non-climacteric, including grapevine berries. Non-climacteric fruits do not exhibit increases in respiration and the production of the plant hormone, ethylene, at the onset of ripening that are characteristic of the many climacteric fruit species. Unlike the well-characterized ethylene signal transduction cascade in climacteric ripening initiation, the molecular mechanisms underlying the control of non-climacteric ripening are poorly understood. Evidence from grapevine suggests that the principal hormones controlling non-climacteric ripening initiation (called 'veraison' by viticulturists) are the plant hormones, abscisic acid and brassinosteroids, while ethylene apparently plays a minor, additive role. In this project, we will identify genes controlling modifications to these hormones which make them inactive in plant cells and characterize potential roles for these genes in regulating veraison in grapevine berries. By better understanding hormone metabolism and other regulatory mechanisms controlling hormone action at veraison, we can identify molecular targets for: 1) developing biomarkers for ripening onset, which viticulturists have indicated would be a beneficial management tool and 2) genetically modifying grapevine to shorten the time from fruit set to veraison, which is desirable for cool climate viticulture in Canada.