Abstract
The role of Shaker-type outgoing potassium channels in the control of grape berry acidityVine (Vitis vinifera L.) is a fruit species with a high economic impact, which is also considered to be a model plant for studying the physiology of acid fruit plants. Today, climate change, characterised by a sharp rise in temperatures and water deficits, is disrupting the development and ripening of grapes. The composition of the berry at harvest has changed, and in particular the fruit, which has become less acidic at harvest, contains excess potassium and sugar, which is detrimental to the production of a quality wine. During grape ripening, it is known that K+ initiates and controls the massive flows of sugar and nutrients needed to load the berry and, as the majority counter-ion, is also involved in the partial neutralisation of the grape's organic acids (tartaric and malic acid). The greater the amount of K+ in the berry at harvest, the less acidic the berry will be.In this context, understanding the adjustment of K+ fluxes during berry ripening in relation to climate change seems crucial.My work focuses on the functional characterisation of Shaker-type potassium channels with outward rectification.The various members of this family are known to dominate potassium conductance at the plasma membrane of plant cells. In grapevine, 4 genes encoding Shaker subunits involved in fluxes allowing K+ to leave the cell have been identified. My thesis work focuses on the study of 3 of these subunits: 1) the VvK5.2 subunit, which has structural and functional features that make it 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 was carefully analysed, 2) the existence of two twin subunits VvK5.3 and VvK5.4 present 95% amino acid identity while having different functional properties. The third part analyses the impact of different climate change parameters on the transcriptome of the grape berry during ripening using an RNA-SEQ.Finally, in the fourth part, the functional characterisation of a Shaker-type K+ channel belonging to the sub-family of weakly rectifying channels is presented in the oil palm (Elaeis guinensis Jacq), which is the world's leading source of vegetable oil.Keywords: vine, potassium, Shaker K+ channel, acidity, wine, temperature increase, oil palm.