The pathogen Moniliophthora perniciosa promotes differential proteomic modulation of cacao genotypes with contrasting resistance to witches´ broom disease.

Abstract

Background: Witches’ broom disease (WBD) of cacao (Theobroma cacao L.), caused by Moniliophthora perniciosa, is one of the main problems limiting cacao production, thus, the development of cacao genotypes with durable resistance is the main challenge for disease control. Proteomic methods are often used to study the interactions between hosts and pathogens, therefore helping classical plant breeding in the development of resistant genotypes. Here, we compared the proteomic alterations of two cacao genotypes standard for WBD resistance and susceptibility in response to M. perniciosa infection at 72 hours and 45 days of post-inoculation. Results: A total of 554 proteins were identified, 246 in the susceptible and 308 in the resistant genotype. The identified proteins were involved mainly in metabolism, energy, defense and oxidative stress. The resistant genotype showed more expressed proteins as well as more variability of proteins associated to stress and defense, while the susceptible genotype showed more repressed proteins. Among these proteins, stand out pathogenesis related proteins (PRs), protein related with oxidative stress regulation, as well as, trypsin inhibitors, that were differentially expressed between genotypes. Interaction networks were predicted analyzing up and down regulated proteins separately. A complex protein-protein interaction was observed, and some proteins showed a high number of interactions. Those proteins may function as cross-talkers between these biological functions. Conclusions: We present the first study reporting the proteomic alterations of resistant and susceptible genotypes in the T. cacao x M. perniciosa pathosystem. Important altered proteins identified are related to key biologic functions in resistance, such as oxidative stress, especially in the resistant genotype, which showed a strong mechanism of detoxification. Also, the positive regulation of defense and stress proteins was more evident in this genotype. Proteins with significant roles against fungus, such as chitinases, trypsin inhibitors and PR 5 were identified and may be good resistance markers. Finally, important biological functions, such as stress and defense, photosynthesis, oxidative stress and carbohydrate metabolism were differentially impacted with M. perniciosa infection in each genotype.