Résumé
The fungus Moniliophthora perniciosa, the etiologic agent of witches' broom disease of cacao (Theobroma cacao L.) has a hemibiotrophic life cycle, with a biotrophic and a necrotrophic phase. The biotrophic phase, initiating the disease, is characterized by a monokaryotic mycelium, while the necrotrophic phase is characterized by a dikaryotic mycelium leading to plant necrosis. During the culture of M. perniciosa on bran-based solid medium, six different developmental phases were observed according to the dikaryotic mycelium color or the organ produced: white, yellow, pink, dark pink, primordium and basidiomata. A proteomic analysis of the different M. perniciosa development stages associated to mass spectrometry allowed the identification of about 250 differentially expressed proteins. In this study, using such differentially expressed proteins, we developed a systems biology analysis to identify physical protein-protein interaction (PPPI) networks related to the fungus development focusing on basidiocarp formation. First, orthologous protein sequences of M. perniciosa were obtained in N. crassa using the BLASTX tool. The data mining screening and PPPI network design associated with fungal development was performed using the Cytoscape software, version 2.5.0. These data were downloaded from the STRING 8.3 database. The interactome networks obtained from this first screening were analyzed with the Molecular Complex Detection software, a Cytoscape plugin, in order to evaluate potential subgraphs that were used further for network expansion. Gene ontology clustering analysis was performed using the Biological Network Gene Ontology software. Moreover, an analysis of centrality was performed using the software Centiscape 1.2.1.; several hub-bottlenecks, hub and bottlenecks proteins, as well as proteins involved in biological processes important for the M. perniciosa development were identified. The main biological processes encountered were anatomy and morphology, reproduction, oxidative stress, cell wall biosynthesis, pigmentation, development and cell differentiation. The identification of proteins involved in the formation of basidiomata, as well as the knowledge about their interactions, may contribute to the future development of witches' broom control strategies. To our knowledge, this is the first system biology analysis of proteins involved in the M. perniciosa life cycle. Supported by: CAPES, CIRAD, BNB, PRONEM/FAPESB. (Texte intégral)