AUTHOR=Xia Chongjing , Wang Meinan , Cornejo Omar E. , Jiwan Derick A. , See Deven R. , Chen Xianming 

TITLE=Secretome Characterization and Correlation Analysis Reveal Putative Pathogenicity Mechanisms and Identify Candidate Avirulence Genes in the Wheat Stripe Rust Fungus Puccinia striiformis f. sp. tritici

JOURNAL=Frontiers in Microbiology

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2017.02394

DOI=10.3389/fmicb.2017.02394

ISSN=1664-302X

ABSTRACT=<p>Stripe (yellow) rust, caused by <italic>Puccinia striiformis</italic> f. sp. <italic>tritici</italic> (<italic>Pst</italic>), is one of the most destructive diseases of wheat worldwide. Planting resistant cultivars is an effective way to control this disease, but race-specific resistance can be overcome quickly due to the rapid evolving <italic>Pst</italic> population. Studying the pathogenicity mechanisms is critical for understanding how <italic>Pst</italic> virulence changes and how to develop wheat cultivars with durable resistance to stripe rust. We re-sequenced 7 <italic>Pst</italic> isolates and included additional 7 previously sequenced isolates to represent balanced virulence/avirulence profiles for several avirulence loci in seretome analyses. We observed an uneven distribution of heterozygosity among the isolates. Secretome comparison of <italic>Pst</italic> with other rust fungi identified a large portion of species-specific secreted proteins, suggesting that they may have specific roles when interacting with the wheat host. Thirty-two effectors of <italic>Pst</italic> were identified from its secretome. We identified candidates for <italic>Avr</italic> genes corresponding to six <italic>Yr</italic> genes by correlating polymorphisms for effector genes to the virulence/avirulence profiles of the 14 <italic>Pst</italic> isolates. The putative <italic>AvYr76</italic> was present in the avirulent isolates, but absent in the virulent isolates, suggesting that deleting the coding region of the candidate avirulence gene has produced races virulent to resistance gene <italic>Yr76</italic>. We conclude that incorporating avirulence/virulence phenotypes into correlation analysis with variations in genomic structure and secretome, particularly presence/absence polymorphisms of effectors, is an efficient way to identify candidate <italic>Avr</italic> genes in <italic>Pst</italic>. The candidate effector genes provide a rich resource for further studies to determine the evolutionary history of <italic>Pst</italic> populations and the co-evolutionary arms race between <italic>Pst</italic> and wheat. The <italic>Avr</italic> candidates identified in this study will lead to cloning avirulence genes in <italic>Pst</italic>, which will enable us to understand molecular mechanisms underlying <italic>Pst</italic>-wheat interactions, to determine the effectiveness of resistance genes and further to develop durable resistance to stripe rust.</p>