Towards improvement of grape and wine qualities through the control of K+ and sugar accumulations. – SweetKaliGrape

Wine is a key component of the French economy, because the quality and the typicity of French wines are largely recognized as a part of the worldwide image of France. Wine quality strongly depends on berry content at harvest. However, climate change is now modifying this content, especially by increasing berry K+ and sugar concentrations at harvest. This trend already observed since several decades in Europe (and farther) results in wines with increasing alcohol contents, more flat, and with decreased ageing potential. The control of the sugar/acid balance of the berries would allow to maintain the typicity, the quality and the market value of French wines. This requires a better understanding of the molecular basis of K+ and sugar accumulations along grape berry development and in response to climate change. SWEETKALIGRAPE aims at characterizing the molecular repertoire of genes and regulatory networks involved in the fine-tuning of the sugar/acid balance of the berries at harvest. To this end, our consortium gathers 3 groups with complementary expertises: (i) a group of plant (electro)physiologists, molecular and cellular biologists who has carried out pioneering work in analysis of molecular mechanisms involved in K+ transport in Arabidopsis, (ii) a group of cellular and molecular biologists working on berry composition (especially sugars), the responses of berry metabolism to environment and the molecular mechanisms involved in these processes and (3) a group of ecophysiologists investigating the adaptation of plants to contrasted climates.
The work programme includes five tasks: (i) Analysis of relationships between berry quality and K+ / sugar contents examined under different climatic scenarios. This experiment will be performed using both current widespread cultivars and particular cultivars of physiological relevance (contrasting by acidity or responses to water stress and heat exposure); (ii) Identification of the molecular repertoire of genes expressed in flesh cells and involved in K+ and sugar accumulations under control, water stress or high temperature conditions through RNA-SEQ analysis, followed by the identification of gene regulatory networks through a systems biology approach (iii) Fine mapping of the subcellular pH in flesh cells allowing to precise the role of the subcellular proton distribution in relation with berry quality (iv) Functional characterization of sugar and K+ channels and transporters identified in task 2 (v) Design of a reverse genetic approach based on VIGS (virus induced gene silencing) technology coupled with transient transformation by agro-infiltrations of berries and precise phenotypic analysis of different mutant plants obtained to precise the role played in planta by K+ channels, sugar transporters and the new candidate genes identified in task 2.
Thanks to the combination of genetic, molecular, electrophysiology and functional analyses, the project will develop an integrated study allowing to understand the control of the grape berry sugar/acid balance under various environments. Moreover, the implementation of a new tool for functional genomic analyses in grapevine will be a significant breakthrough because transformed berries will be available within one year. Three to four years are usually needed when grapevine classical stable transformation is used to obtain fruits that may be studied. Finally, this work will open new research lines through the analysis of new genes playing an important role in the berry quality and will provide an improved basis for the selection of vines adapted to our future environment.