Death be not proud – rcs5 is a wall associated kinase gene that functions as a dominant susceptibility factor in the Barley- Cochliobolus sativus interaction to produce necroptosis
G. AMEEN (1), T. Drader (2), L. Sager (1), B. Steffenson (3), A. Kleinhofs (2), R. Brueggeman (1) (1) Department of Plant Pathology, North Dakota State University, U.S.A.; (2) Department of Crop and Soil Science, Washington State University, U.S.A.; (3) Department of Plant Pathology, University of Minnesota, U.S.A.

The Cochliobolus sativus, Rcs5 R-gene is located on the short arm of barley chr 7H. High-resolution genetic mapping delimited Rcs5 to ~0.32cM. Previous attempts to validate candidate genes in the region failed as efforts focused on finding a functional resistance gene in resistant cultivars. However, genetic analysis of an F2 population between the susceptible cv, Steptoe and resistant cv Morex showed a 1 (res):3 (sus) segregation ratio suggesting that rcs5 resistance is recessive in nature. Utilizing the barley genome sequence of cv Morex, four wall-associated kinase (WAK) genes, designated as HvWAK2-5, were identified in the delimited physical region containing rcs5. Functional validation of the candidate genes using BSMV-VIGS revealed that silencing either HvWAK3 or HvWAK4, shifted susceptibility to resistance in cvs Steptoe and Harrington and produced no response in the resistant cv Morex. Thus, we hypothesize that coherent function of both proteins elicits susceptibility. Genome walking and cDNA analysis of both genes revealed that HvWAK3 is polymorphic, having a 620 bp insertion in the susceptible cvs encoding a putative Ca2+ binding domain that is absent in Morex indicating that HvWAK3 is the spot blotch resistance gene rcs5. We hypothesize that HvWAK3 encodes the Rcs5 dominant susceptibility protein targeted by the necrotrophic pathogen C. sativus to induce programmed cell death in an inverse-gene-for-gene manner facilitating disease in the susceptible lines.

Abstract Number: P17-486
Session Type: Poster