Ph. D. Eloïse METEIER

SWEET sugars transporters in grapevine: role in interaction with bio aggressors.

Defended on July 2, 2019, in Colmar

Supervisor: Pr. Julie Chong, University of Haute Alsace

Thesis co-supervisor: PhD. Pere Mestre, Research Fellow, INRA of Colmar

Abstract

Transport and allocation of sugars play a major role in plant/pathogen interactions. Plant SWEET sugar transporters are the target of extracellular pathogens that modify their expression in order to acquire sugars necessary for their growth. The study of SWEET sugar transporters in grapevine and more particularly their role in the interactions with pathogens has been carried out by focusing on three of them: VvSWEET2a, VvSWEET4 and VvSWEET17d. By using hairy roots overexpressing VvSWEET4, we were able to show the glucose transport activity of VvSWEET4 in planta. Moreover, our results have shown that the overexpression of this gene leads to an increase in root hexose content as well as to the induction of the expression of several genes of the flavonoid biosynthesis pathway, associated with an increase in proanthocyanidins levels. These results explain the enhanced resistance of VvSWEET4 overexpressors to Pythium irregulare, a soil born pathogen. The search for a non-functional VvSWEET4 transporter within the Vitaceae led to the identification of three amino acids important for the glucose transport function. These amino acids have so far never been identified as important for the sugar transport activity of different SWEET transporters in other species. We also observed a phenomenon of compensation between two mutations allowing a restoration of the glucose transport activity.