Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: April 5, 2006
Publication Date: July 29, 2006
Citation: Luster, D.G., Mcmahon, M.B., Carter, M.L. 2006. Characterization of proteins secreted by phakopsora pachyrhizi during spore germination. Phytopathology. 96:S71 Technical Abstract: Phakopsora pachyrhizi is the causal agent of Asian soybean rust, a disease of leguminous plants that has recently become established in the U.S. We have identified a set of extracellular proteins present at 18 hrs in P. pachyrhizi urediniospore germination water and wash media, using two-dimensional gel electrophoresis and Matrix-Assisted Laser Desorption/Ionization mass spectrometry of tryptic peptides. Peptide sequences identified from the putative secreted proteins were mapped to a set of six cDNA clones from an EST sequence database derived from germinating P. pachyrhizi urediniospores. Only one (containing a putative transaldolase catalytic site) of the six cDNA’s has any similarity to proteins in GenBank, SwissPROT or other databases; the remaining five remain unidentified as to function. ORF’s from the 6 proteins were submitted to protein motif searches using several web-based recognition algorithms. All six of the secreted proteins contained amino acid motifs for N- or O- linked glycosylation and protein kinase phosphorylation. Searches for signal peptide sequences at N-termini were inconclusive using Neural Network and Hidden Markhof model algorithms (SignalP 3.0; http://www.cbs.dtu.dk/services/SignalP/) possibly indicative of the paucity of secreted basidiomycete fungal proteins in databases. Polyclonal antibodies raised to the extracellular protein fraction from germinating urediniospores are being used to characterize and localize the proteins in the extracellular spore matrix.