Comparative Analysis of the Stage- and Species-Specificity of Rust Secretomes.

• Applicant: Professor Dr. Ralf Thomas Vögele
• Subject Area: Organismic Interactions, Chemical Ecology and Microbiomes of Plant Systems
• Term: from 2006 to 2012
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 34569014

Obligate biotrophic fungi are characterized by a prolonged co-existence of host and parasite. It is highly likely that proteins, so called effectors, are involved in establishing and maintaining this intricate interaction. A hallmark of obligate biotrophs is the formation of specially differentiated hyphae, so called haustoria, penetrating into the host cell. These haustoria are the ideal place for a transfer of effectors into the interface between host and parasite or even into the host cell itself.The haustorial secretome of Uromyces fabae was analyzed and compared to the secretome of in vitro grown infection structures representing developmental stages prior to the parasitic stage. We found 62 genes encoding proteins secreted from haustoria and 42 genes encoding proteins secreted from in vitro grown infection structures. Four of these genes were present in both libraries. These results indicate a strong stage-specificity of protein secretion in rusts. Similarities were found for 39 of the sequences, 28 of which showed similarity to proteins identified among other rusts only. This was taken as evidence for roles of these proteins in virulence/pathogenicity and host specificity unique to the Uredinales. Selected proteins were localized immunocytologically and searches for interaction partners have been initiated. One candidate effector protein, Uf- HSP25p, could be localized within the plant cell nucleus. Both experimental approaches will be further pursued. During the second phase of the project we intend to analyze the haustorial secretomes of Phakopsora pachyrhizi and Uromyces appendiculatus by using the yeast signal sequence trap established with U. fabae. This will create opportunities to compare the different secretomes and identify secreted proteins essential for virulence/pathogenicity.

• DFG Programme: Research Grants