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Proteomic Comparison of Needles from Blister Rust-Resistant and Susceptible Pinus strobus Seedlings Reveals UpRegulation of Putative Disease Resistance Proteins

¹Department of Plant Pathology, University of Minnesota, 495 Borlaug Hall, 1991 Upper Buford Cir., St. Paul, MN 55108, U.S.A.; ²Department of Biochemistry, Molecular Biology/Biophysics, University of Minnesota, 140 Gortner Lab 1479 Gortner Ave., St. Paul, MN 55108, U.S.A.; ³Department of Forest Resources, University of Minnesota, North Central Research and Outreach Center, Grand Rapids, MN 55744, U.S.A.; ⁴Department of Horticultural Science, University of Minnesota, 305 Alderman Hall 1970 Folwell Ave., St. Paul, MN 55108, U.S.A.

In order to characterize a hypersensitive-like reaction in selected Pinus strobus seedlings to Cronartium ribicola, a proteomic comparison of needles from resistant and susceptible seedlings was undertaken using two-dimensional gel electrophoresis (2-DE). The results revealed 19 polypeptides specific to resistant seedlings and seven of these specific to infected resistant seedlings. There were 13 polypeptides up-regulated (≥3-fold increase) in resistant family P327 in comparison to needle tissue from susceptible and mock-inoculated seedlings. Electrospray ionization liquid chromatography and tandem mass spectrometry was used to sequence 11 proteins from the 2-DE gels. Sequences obtained from electrospray ionization liquid chromatography and tandem mass spectrometry were used for MS-BLAST and Pro-ID database searches allowing identification with a 95 to 99% confidence level. Six proteins were determined to be homologs of proteins with known roles in disease resistance, five were determined to be homologs of members of the leucine-rich repeat (LRR) superfamily, and one was a homolog of heat shock protein 90, a protein that serves as a cofactor for certain LRR proteins. This is the first report of members of the LRR family with functional homologs in Pinus strobus and of a molecular basis for white pine blister rust resistance in Pinus strobus.

Additional keywords: LRR disease resistance.