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Genomic Analyses Reveal Localized Effector Diversification and Candidate SnTox5 in Parastagonospora nodorum

Jonathan Richards: Plant Pathology Department, North Dakota State University

<div><em>Parastagonospora nodorum</em>, a necrotrophic fungal pathogen of wheat, utilizes an array of effectors to intentionally elicit programmed cell death. These molecules are typically small secreted proteins (SSPs), may be cysteine-rich, and lack conserved domains or homology with other organisms. Eight <em>P. nodorum-</em>wheat interactions have been identified and three effectors have been cloned, including SnToxA, SnTox1, and SnTox3. However, little is known of the genic diversity of potential effectors within populations in the USA and the effectors underlying previously identified interactions remain to be cloned. Genome sequencing of 175 <em>P. nodorum </em>isolates led to the identification of 322,613 SNPs/INDELs, including 132,650 nonsynonymous SNPs. Results show the population-specific accumulation of nonsynonymous SNPs in effector candidates, with 24 and 15 genes from the Midwest and South/East populations, respectively, containing more than two nonsynonymous SNPs/kb. Additionally, 48 SSPs exhibited presence/absence variation (PAV) throughout the entire population. GWAS using SNP/INDEL/PAV markers identified a SSP with PAV strongly associated with virulence on the SnTox5 differential line LP29 and durum wheat line Scoop1. This gene is currently being validated via heterologous expression and gene-disruption transformants. Results of this research illustrate the population-specific diversity present in effector candidates and the utility of pathogen GWAS for effector identification.</div>