Submitted to: Phytopathology
Publication Type: Abstract Only
Publication Acceptance Date: 4/30/2008
Publication Date: 8/15/2008
Citation: Luster, D.G., Mcmahon, M.B., Carter, M.L. 2008. A small family of Phakopsora pachyrhizi proteins localized to the spore wall. Phytopathology. 98:S95
Technical Abstract: Phakopsora pachyrhizi is the causal agent of Asian soybean rust, which has become established over an expanding range in the U.S. We previously identified and characterized a set of extracellular proteins recovered from P. pachyrhizi urediniospore germination media. Immunolocalization studies confirm an extracellular location for the proteins in the spore wall. Functional inhibition assays with antibodies are being applied to identify a role for the proteins in fungal growth, development and/or infection. Two proteins of near identical length (Phap107; 108 AA and Phap369; 109 AA) with 64 percent identical amino acid sequences and 76 percent amino acid class similarity were selected for further study. These proteins are not significantly similar to any sequences deposited in open source databases. PHAP369 was mapped to a set of fosmid clones resulting from shotgun genomic sequencing of P. pachyrhizi. Analysis of fosmid and EST sequences from P. pachyrhizi revealed four ORFs and one truncated EST with closely related sequence and intron/exon structure to Phap369, thus constituting a small protein family. No ORFs closely related to Phap107 were found in the fosmid library, but the sequence and structure of Phap107, generated from genomic DNA, was similar to that of the 369 ESTs. Prediction analyses of the N-terminal regions of these proteins do not produce signal peptide prediction scores indicative of a signal sequence, and yeast secretion trap assays with clones 369 and 107 were negative. Amino acid sequence analysis of the N-terminal region revealed that while distinct hydrophobic and charged domains are present in the region, a signal domain motif is not evident. Results from Southern blot analysis will also be presented to complete the analysis of gene structure and copy number of related members of the protein family.