Characterization of a secreted nucleoside phosphorylase in Colletotrichum graminicola

JOSÉ M. SANZ MARTÍN; MANUEL GONZÁLEZ FUENTE; WALTER A. VARGAS; MICHAEL R. THON ; SERENELLA SUKNO

Conferencia; 12th European Conference in Fungal Genetics; 2014

The maize pathogen Colletotrichum graminicola is the causal agent of leaf anthracnose and stalk rot. C. graminicola secretes effector proteins that disable plant defense components and promote successful infection. We performed a genome-wide survey of C. graminicola proteins that are predicted to encode a secretion signal peptide and have evidence of nuclear localization and/or DNA binding domains. One of the proteins identified in this screen, GRLG_00879, is predicted to encode a secretion signal, a nucleoside phosphorylase domain, and a highly basic C terminal domain. Nucleoside phosphorylase domains are typically involved in nucleoside modification processes and repair of DNA damage and are usually found in the nucleus. The basic C terminal region has an isoelectric point of 10.74, and has a characteristic arginine pattern that may define a DNA interaction domain. This protein has no similarity with previously described pathogenicity factors and there are no homologs in public databases. The presence of these two very different domains led us to suggest that it could have evolved as a fusion of two distinct proteins. We prepared transcriptional fusion constructs with the promoter and a GFP reporter gene for use in microscopic studies. We also performed qPCR assays to determine the expression pattern of this gene. The expression assays show that the gene is expressed during the early stages of the infection process and it was confirmed with the microscopic studies. We hypothesize that this protein is localized to the host nucleus during the early staged of infection, where it modulates the host immune system. To test this hypothesis, we are preparing translational RFP (mCherry) fusion protein constructs as well as constructing null mutants for use in pathogenicity assays. The study of this gene and the encoded protein will reveal its role, if any, in the regulation of the host´s immune system during the infection process.