Gene Expression and Interactome Analysis of Candidate Effectors Associated with Pre- and Post-Haustorial Hemileia vastatrix-Coffee Interaction

Abstract

The present study sought to analyze the putative secreted proteins of Hemileia vastatrix , with potential to function as effector proteins. The H. vastatrix secretome was subjected to functional categorization and the greatest similarities were observed between species of the genus Puccinia sp (398), and Melampsora larici-populina (82). Based on the secretome, 415 Gene Ontology terms were extracted. The putative secretome was also compared to the high-throughput transcriptome of coffee- H. vastatrix interactions. By the transcriptome comparison data and the results of functional annotation and characteristics associated with effector proteins, 15 genes were selected and analyzed using RT-qPCR during compatible and incompatible coffee- H. vastatrix interactions. The expression patterns suggested that the EHv33-18 and EHv33-25 candidate effector may be responsible for faster communication between pathogen and the host during incompatible interaction. Other six candidate are involved in the biotrophic stage of infection, which is characterized by an increase in the expression of effectors, and in enzymes involved in secondary metabolism. Phylogenetic analysis suggest that these eight genes follow evolutionary mechanisms exclusive to the coffee- H. vastatrix interaction, making them important targets in studies aimed at obtaining durable resistance to this disease. Interactomic network made between coffee proteins and H. vastatrix proteins was obtained for the first time and revealed a wide network of interactions between effector EHv33-19 and coffee proteins. The obtained results suggest that there may be communication between the pathogen and the host in the early stage of infection during the urediniospores germination phase. This indicated pre-haustorial resistance complementary to post-haustorial resistance.