Doctorate thesis of Montpellier University


Wednesday december 14 at 14h pm, Amphi Philippe Lamour


Role of outward potassium channels in the control of grape acidity

Doctoral school : GAIA – Biodiversité, Agriculture, Alimentation, Environnement, Terre, Eau
Spéciality : BIDAP – Biologie, Interactions, Diversité Adaptative des Plantes
University : Université Montpellier
Reasearch unit : IPSiM –  Institut for Plant Sciences of Montpellier

Team: KaliPHruit


Sébastien THOMINE, Directeur de recherche, CNRS-I2BC-Gif du Yvette                             Rapporteur
Pierre-Emmanuel COURTY, Directeur de recherche, INRAE-Dijon                                        Rapporteur
Manuel NIEVES-CORDONES, chercheur, CSIC-Murcia Espagne                                            Examinateur
Pierre CZERNIC, Professeur des université UM, Université de Montpellier                           Examinateur
Mme Isabelle GAILLARD, Directrice de recherche, INRAE-Montpellier, UMR IPSiM             Directrice de thèse
Mme Teresa CUELLAR-SANCHEZ, Chercheuse CIRAD, CIRAD-Montpellier, UMR AGAP     Co-directrice de thèse
Alexis DE ANGELIS, directeur de recherche, CNRS-Montpellier, UMR IPSiM                         Invité


Grapevine (Vitis vinifera L.) is a fruit species with a high economic impact, which is also considered a model plant to study the physiology of acidic fruit plants. Today, climate change, characterized by a strong increase in temperature and water deficits, is disrupting the development and ripening of grapes. As a result, the composition of the berry at harvest is modified, and in particular, this fruit, which has become less acidic and contains an excess of potassium and sugar, which is deleterious to the production of high-quality wine. During grape ripening, it is known that K+ initiates and controls the massive flow of sugar and nutrients needed to load the berry and is, as the major counterion, also involved in the partial neutralization of organic acids in the grape (tartaric and malic acid). The higher the amount of K+ in the berry at harvest, the less acidic the berry will be. In this context, the understanding of the adjustment of K+ fluxes occurring during the ripening of the grape in relation to climate change is crucial. My work focuses on the functional characterization of Shaker-type outward potassium channels. The different members of this family are known to dominate potassium conductance at the plasma membrane of plant cells. In grapevine, four genes encoding Shaker subunits involved in fluxes allowing K+ exit from the cell have been identified. My thesis work focuses on the study of 3 of these subunits. The first is the VvK5.2 subunit which presents structural and functional particularities conferring its role as a positive regulator of the activity of the outward and weakly rectifying channels in which it is present. The interaction of VvK5.2 with these different Shaker subunits has been carefully analyzed. The second is the existence of two twin subunits VvK5.3 and VvK5.4 which share 95% amino acid similarity despite having distinct functional characteristics. The third analyzes the impact of different climatic parameters of climate change on the transcriptome of the grape berry during its maturation via an RNA-SEQ. Finally, in the fourth research axis, the functional characterization of a Shaker-type K+ channel belonging to the subfamily of weakly rectifying channels is investigated in oil palm (Elaeis guinensis Jacq), the species that is the first source of vegetable oil in the world.
Keywords: grapevine, potassium, K+ Shaker channel, acidity, wine, temperature increase, oil palm.