Infectious process and intraspecific diversity of Colletotrichum lupini, a fungal pathogen responsible for lupin anthracnose
Résumé
Lupin anthracnose is a major threat caused by the filamentous fungus Colletotrichum lupini. The genus Colletotrichum includes a wide number of phytopathogen species distributed worldwide. They were classified into 14 species complexes, with C. lupini belonging to the C. acutatum species complex. To date, studies performed on C. lupini, aimed at better understanding its phylogenetic classification and infectious lifecycle. But additional studies seemed necessary to increase our knowledge on (i) intraspecific diversity within the C. lupini species and (ii) the molecular determinants of pathogenicity. To address the first objective, a study was performed on strains from official collections and from isolates recently collected in the west of France. A low intra-specific phylogenetic diversity was found compared to the phenotypic diversity, notably characterized by contrasted aggressiveness between strains. The second objective was evaluated by determining fungal gene expression and protein synthesis during lupin infection by C. lupini using, respectively, a RNAseq-based transcriptomic approach and a mass spectrometry-based proteomic approach with a nLC Q-exactive Orbitrap. Taken together, our results highlighted that the dynamics of symptoms, gene expression and protein synthesis shared similarities to those of hemibiotrophic pathogens. In addition, few genes of unknwown or poorly-described functions were found to be specifically associated to the early or late stages of infection, suggesting that they may be of importance for pathogenicity. Functional validation will be discussed to confirm their role in promoting C. lupini pathogenicity.