A proteomic study of the tripartite interaction of wheat, Fusarium graminearum and an endophytic streptomycete during normal and drought conditions

Fusarium graminearum is one of the main pathogen of Triticum aestivum causing Fusarium head blight (FHB) and Fusarium crown rot (FCR), contaminating grains with mycotoxins. Streptomyces sp. DEF39 was previously described to be able to colonize systemically wheat plants after seed treatment and to reduce disease and deoxynivalenol contamination in grains, during field trials. Under drought stress, DEF39 induced a shortening of the life cycle in seed inoculated plants, without affecting the grain production. This work aims to study the bacteria-plant-fungus crosstalk during their tripartite interaction, deciphering the mechanism of action of the DEF39 strain. An in-vitro system was developed to assess the interactions, comparing the wheat root proteome of plants exposed to 4 treatments both in normal and drought conditions: the control plant, the DEF39 seed inoculated plant, the F. graminearum infected plant and the DEF39 seed inoculated infected by the fungus. The 1D GeLC-MS/MS approach allowed to quantify more than 300 proteins, of which about 90% belongs to wheat. The root proteome changed in response both to the fungus, DEF39, their interaction and water availability. The major effect was induced by the fungal infection, involving primary and redox metabolism, transport, and defence. Interestingly, the plant responses were also influenced by the seed inoculation, suggesting that Streptomyces sp. DEF39 has an effect on the plant defence mechanisms against different stress.