Poster Session: MPMI-Fungi

582-P

Differential expression of the pathogenesis-related protein 1 (PR-1) gene family in stem rust (Puccinia graminis f. sp. tritici)-wheat interactions.
S. LU (1), T. L. Friesen (1), J. D. Faris (1)
(1) USDA-ARS, Cereal Crops Research Unit, Fargo, ND, U.S.A.

The group 1 pathogenesis-related (PR-1) proteins, known as hallmarks of defense pathways, are encoded by a multigene family in hexaploid wheat (Triticum aestivum L.) that includes at least 12 closely related TaPr-1 genes responsive to infection by the necrotrophic pathogen Stagonospora nodorum (Sn). Here we report an expression analysis of the same set of TaPr-1 genes in response to the biotrophic stem rust (SR) fungus Puccinia graminis f. sp. tritici. A SR-resistant cultivar (Bobwhite) and three susceptible lines (derived from Bobwhite) were grown and inoculated in the greenhouse under the same conditions. Reverse transcriptase PCR using TaPr-1-specific untranslated region-specified discrimination primers revealed that most Sn-inducible TaPr-1 genes were also expressed in SR-wheat interactions, but the expression patterns differed significantly. Two TaPr-1 genes that are up-regulated in both incompatible and compatible Sn-wheat interactions were found to be induced only in the SR-infected resistant line that showed a hypersensitive response (HR). In susceptible lines, several TaPr-1 genes were expressed in un-inoculated plants, but not (or at a lower level) in inoculated plants that developed stem rust symptoms. These results suggested that PR-1 proteins play important roles in HR-based resistance and are controlled by independent defense pathways in necrotrophic vs. biotrophic pathogen-wheat interactions.
Keywords: Fungus, Cereals-Grains, Wheat