Location: Foreign Disease-Weed Science ResearchTitle: Rpp1 encodes a ULP1-NBS-LRR protein that controls immunity to Phakopsora pachyrhizi in soybean
|PANDEY, AJAY - Iowa State University
|WHITHAM, STEVEN - Iowa State University
Submitted to: Molecular Plant-Microbe Interactions
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/4/2018
Publication Date: 11/19/2018
Citation: Pedley, K.F., Pandey, A.K., Ruck, A.L., Lincoln, L.M., Whitham, S.A., Graham, M.A. 2018. Rpp1 encodes a ULP1-NBS-LRR protein that controls immunity to Phakopsora pachyrhizi in soybean. Molecular Plant-Microbe Interactions. 32:120-133.
Interpretive Summary: Asian soybean rust is one of the most devastating diseases of soybean. Yield losses resulting from the disease are significant and the disease occurs in all major soybean growing regions of the world. Screening for resistance in soybean has identified several sources of resistance. However, the exact identity of the genes that confer resistance remain largely unknown. In this study, we identify a gene that controls one form of resistance to the soybean rust pathogen. Characterization of the gene revealed a novel structure, which provides insight into the mechanisms underlying resistance. These findings provide fundamental information regarding resistance to soybean rust, which are anticipated to assist in the development of improved soybean lines and to provide insight into the mechanism all plants use to thwart pathogens.
Technical Abstract: Phakopsora pachyrhizi is the causal agent of Asian soybean rust. Susceptible soybean plants infected by virulent isolates of P. pachyrhizi are characterized by tan-colored lesions and erumpent uredinia on the leaf surface. Germplasm screening and genetic analyses have led to the identification of seven loci, Rpp1 – Rpp7, that provide varying degrees of resistance to P. pachyrhizi (Rpp). Two genes, Rpp1 and Rpp1b, map to the same region on soybean chromosome 18. Rpp1 is unique among the Rpp genes in that it confers an immune response (IR) to avirulent P. pachyrhizi isolates. The IR is characterized by a lack of visible symptoms, whereas resistance provided by Rpp1b – Rpp7 results in red-brown foliar lesions. Rpp1 maps to a region spanning approximately 150 Kb on chromosome 18 between markers Sct_187 and Sat_064 in L85-2378 (Rpp1), an isoline developed from Williams 82 and PI 200492 (Rpp1). To identify Rpp1, we constructed a bacterial artificial chromosome (BAC) library from soybean accession PI 200492. Sequencing of the Rpp1 locus identified three homologous nucleotide binding site-leucine rich repeat (NBS-LRR) candidate resistance genes between Sct_187 and Sat_064. Each candidate gene is also predicted to encode an N-terminal ubiquitin-like protease 1 (ULP1) domain. Co-silencing of the Rpp1 candidates abrogated the immune response in the Rpp1 resistant soybean accession PI 200492, indicating that Rpp1 is a ULP1-NBS-LRR protein and plays a key role in the IR.