Submitted to: American Phytopathological Society Annual Meeting
Publication Type: Abstract Only
Publication Acceptance Date: March 12, 2008
Publication Date: July 26, 2008
Citation: Bolton, M.D., Kolmer, J.A., Xu, W.W., Garvin, D.F. 2008. Comparative transcript profiling of Lr1- and Lr34-mediated leaf rust resistance in wheat [abstract]. American Phytopathological Society Annual Meeting, July 26-30, 2008, Minneapolis, Minnesota. p. S24. Technical Abstract: Leaf rust caused by the fungus Puccinia triticina is a widespread disease of wheat. Host resistance strategies to control leaf rust have relied upon race-specific and non-race specific leaf rust resistance (Lr) genes. Although race-specific Lr genes are efficient in halting pathogen growth, high levels of genetic variation in P. triticina often lead to rapid decline in their effectiveness. In contrast, non-race specific Lr genes confer durable resistance to P. triticina and condition a partial resistance phenotype that slows pathogen proliferation. This study compared changes in wheat gene expression associated with 1) a compatible interaction between wheat and P. triticina, 2) resistance encoded by a typical race-specific resistance gene Lr1, and 3) race non-specific resistance encoded by Lr34. Thatcher wheat and near-isolines harboring either Lr1 or Lr34 were inoculated with P. triticina and transcript profiles were assessed at two timepoints using the Affymetrix wheat GeneChip. Surprisingly, no differentially expressed genes were detected in Lr1 plants at either timepoint, while in the compatible interaction differentially expressed genes were detected only at 7 dpi. Genes upregulated in the Lr34 line included those encoding defense and stress-related proteins, secondary metabolism enzymes, and genes involved in transcriptional regulation and cellular signaling. Our results also indicate that the Lr34-mediated defense response is energetically costly, based on coordinated up-regulation of genes in several aerobic and anaerobic primary metabolic pathways that provide a means to produce more ATP. Thus, at the molecular level the modes of action of the leaf rust resistance genes Lr34 and Lr1 are distinctly different.