Ph. D. Gaëlle LE HENANFF

Functional characterization of signaling genes involved in grapevine defence responses to biotic stresses.

Holded in September 2009

Under the direction of Bernard WALTER.

 

Abstract

Vitis vinifera is susceptible to many pathogens, thus requiring a massive use of phytochemicals. Alternative methods have to be developed. In the model plant Arabidopsis thaliana, the AtNPR1, AtNDR1 and AtEDS1 genes are components of the salicylic acid (SA) signalling pathway involved in resistance to biotrophic pathogens. Using a candidate gene approach, we have identified putative orthologs of these genes in the grapevine genome (VvNPR1.1, VvNPR1.2, VvNHL 1 and VvEDS1). Our work shows that VvNPR1-GFP fusion proteins are localized in the nucleus. Moreover, transient overexpression of VvNPR1 genes induces defence gene expression, in bath heterologous and homologous systems. Overexpression of VvNPR1.1 in npr1 mutants restores the different phenotypes of the mutants, while VvNPR1.2 overexpression does not. These results strongly suggest that VvNPR1.1 is the AtNPR1 ortholog. Overexpression of VvNHL 1 in ndr1 mutants does not restore resistance to Pseudomonas syringae. However, resistance to Botrytis cinerea in these plants is weakened, probably because of stimulation of cell death. Furthermore, VvNHL1 repression following B. cinerea infection in V. vinifera could be considered as a defence mechanism against necrotrophic pathogens and suggests that VvNHL1 is involved in promotion of cell death. VvEDS1 expression is induced by pathogens infection and SA treatment. VvEDS1 functional characterization is in progress using eds1 Arabidopsis mutants overexpressing VvEDS1. Knowledge of defence signaling pathways in V. vinifera will contribute to obtain pathogen resistant grapevines.