Satyanaryana Gouthu, Landry Rossdeutch, Victor Puoci, Zachary Goode, Grace Cheng, and Laurent Deluc*
*Oregon Wine Research Institute, Oregon State University, 4017 ALS Building, 2750 SW Campus Way, Corvallis, OR 97331 (laurent.deluc@oregonstate.edu)

In the light of evolving climactic conditions control of ripening initiation will be a major trait of interest for winegrape production. The current research project aims to validate the role of VitviARF4 on the timing of ripening initiation. Three objectives were designed to achieve this goal: 1) characterization of VitviARF4 through genetic engineering using the microvine model, by either inducing or silencing VitviARF4 expression, and validation of its protein interactors during ripening; 2) identification of ripening-related genes directly under the control of VitviARF4; and finally 3) altering VitviARF4 activity to determine its effect on fruit composition at harvest. Since June 2016 we have been able to achieve several milestones on the current project. As part of objective 1, we established the microvine system at OSU and recently conducted our first attempt at genetic engineering. Using a protein-protein interaction assay, we have identified 170 potential protein partners to VitviARF4, some associated with ABA-, sugar- and ethylene-signaling. This might confirm the likely role of VitviARF4 in the interplay that takes place during the ripening initiation between hormones and sugar. For objective 2, we finalized a cloning procedure for the different constructs designed to induce or silence VviARF4 in the microvine plants. For objective 3, we adapted a new analytical method to measure metabolites associated with organic, amino, and phenolic acids, different types of carbohydrates, polyols, and three classes of flavonoids (anthocyanins, flavonols, and monomer and dimer of tannins). For those metabolites, we built an in-house library of 95 analytes and tested it against mass spectral data from berry extracts. We identified 30 analytes covering major compounds existing in ripe grape berry. These include tartrate, malate, glucose, fructose, sucrose, and several polyphenol-related compounds.

Funding Support: Oregon Wine Board, Erath Family Foundation and Fermentation Initiative