Pectinases (pectin methylesterases [PMEs], polygalacturonases [PGs] and protopectinases) are enzymes involved in the degradation of the pectic molecule, which is the main component of the plant middle lamella. Phytopathogens produce such enzymes, which are very important for their virulence. The witches' broom disease, caused by the hemibiotrophic basidiomycete Moniliophthora perniciosa, has committed the cacao production in South Bahia, Brazil. Moniliophthora perniciosa genome sequencing revealed the presence of homologous of pectinase genes. The objective of this work was to obtain a physical protein-protein interaction network by systems biology, generated from a M. perniciosa polygalacturonase (MpPG2). The search for Neurospora crassa MpPG2 ortholog was performed using the reciprocal Blast. The network was obtained in http://string-db.org/ with the NCU02369 ortholog and presented 683 nodes. For the network study, we used the Cytoscape software in which the following analyses were made: i) centrality which revealed 30 bottlenecks including the MpPG2, 149 hubs and 142 hubs-bottleneck; ii) modularity which allowed the identification of 6 clusters; and iii) gene ontology. The NCU10045 is a pectinesterase which interacts in the network with NCU02369-MpPG2; it was also related to other proteins such as the NCU05063 glycosyl hydrolase or with the NCU06326.1 pectate lyase-1. Thus, it was possible to suggest that pectinases and hydrolases were found in the network and interacted directly or indirectly with NCU02369-MpPG2 forming a set of enzymatic activity that may be crucial for host invasion. (Resume d'auteur)