Abstract
Fusarium head blight (FHB), caused mainly by Fusarium graminearum, is the foremost destructive disease of cereals worldwide. Effector-like molecules produced by F. graminearum play key roles in the infection process and are assumed to be one of the essential components of the pathogen’s aggressiveness. However, their nature and role in the disease are still largely misunderstood. As a mean to provide relevant information about the molecular determinism of F. graminearum aggressiveness, we surveyed three F. graminearum strains on three wheat cultivars contrasted by their susceptibility to FHB. F. graminearum strains revealed large differences in aggressiveness which were mostly unchanged when facing hosts of contrasted susceptibility, suggesting that their behavior rely on intrinsic determinants. Surveying the fungal mass progress and the mycotoxin production rate in the spikes did not evidence any simple relationship with aggressiveness differences, while clues were found through a qualitative and quantitative characterization of the three strain proteomes established in planta especially with regards to early synthesized putative effectors. Independently of the wheat cultivar, the three F. graminearum strains produced systematically the same protein set during the infection but substantial differences in their abundance enabled the categorization of fungal aggressiveness. Overall, our findings show that the contrasts in F. graminearum aggressiveness were not based on the existence of strain-specific molecules but rather on the ability of the strain to ensure their sufficient accumulation. Protein abundance variance was mostly driven by the strain genetics and part was also influenced by the host cultivar but strain by cultivar interactions were marginally detected, depicting that strain-specific protein accumulations did not depend on the host cultivar. All these data provide new knowledge on fungal aggressiveness determinants and provide a resourceful repertoire of candidate effector proteins to guide further research.
Highlights
Plants are constantly subjected to biological pressures that could compromise their development
Fuzzy C-means clustering (Kumar and Futschik, 2007) of F. graminearum proteins showing significant abundance changes according to each effect tested (i.e., S and Cultivar effect (Cv)) and their addition (i.e., Strain+Cultivar effect (S+Cv)) was performed from Z-score transformed values and a fuzzification parameter of 2
The evaluation of the aggressiveness of three F. graminearum strains were at first measured via three parameters: (i) the induction of symptoms, (ii) the development of the fungus in spike tissues, and (iii) the DON synthesis rate
Summary
Plants are constantly subjected to biological pressures that could compromise their development. Effector proteins can be localized in the cell wall surface or secreted directly into the plant cells to target specific host functions (Kamoun, 2006; Lo Presti et al, 2015; Sperschneider et al, 2016; Jones et al, 2018). They can play crucial roles in the degradation of complex compounds like the plant cell wall, in the initiation of infection and for obtaining nutrients from plant host reserves (Hao et al, 2019). Effector proteins are probably an essential component of the pathogen’s aggressiveness, the molecular mechanisms underlying their functions are for the most part unknown, especially in fungus (Yi and Valent, 2013; van Schie and Takken, 2014; Jia and Tang, 2015; Lo Presti et al, 2015)
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