Novel Phakopsora pachyrhizi extracellular proteins are ideal targets for immunological diagnostic assays
Douglas G Luster1, Michael B McMahon, H Herb Edwards
1USDA, Agricultural Research Service, Foreign Disease-Weed Science Research Unit, Ft. Detrick, MD, USA.
Abstract:
Phakopsora pachyrhizi, the causal agent of Asian soybean rust (ASR), continues to spread across the southeast and midsouth regions of the United States, necessitating the use of fungicides by producers. Our objective in this research was to identify ASR proteins expressed early during infection for the development of immunodiagnostic assays. We have identified and partially characterized a small gene family encoding extracellular proteins in the P. pachyrhizi urediniospore wall, termed PHEPs (for Phakopsora extracellular protein). Two highly expressed protein family members, PHEP 107 and PHEP 369, were selected as ideal immunodiagnostic targets for antibody development, after we detected PHEPs in plants as early as 3 days postinfection (dpi). Monoclonal antibodies (MAbs; 2E8E5-1 and 3G6H7-3) generated against recombinant PHEP 369 were tested for sensitivity against the recombinant protein and extracts from ASR-infected plants and for specificity against a set of common soybean pathogens. These antibodies should prove applicable in immunodiagnostic assays to detect infected soybeans and to identify ASR spores from sentinel surveillance plots.
Insights
Researchers identified early infection proteins (PHEPs) from Asian soybean rust (ASR) fungi. Antibodies targeting these proteins can detect ASR in soybeans and monitor spore spread.
Area of Science:
- Plant Pathology
- Molecular Biology
- Immunology
Background:
- Phakopsora pachyrhizi causes Asian soybean rust (ASR), a significant threat to soybean production in the US.
- Fungicide use is necessary but early detection of ASR is crucial for effective management.
Purpose of the Study:
- To identify proteins expressed early during P. pachyrhizi infection for developing immunodiagnostic assays.
- To find reliable biomarkers for early detection of Asian soybean rust.
Main Methods:
- Identified and characterized a gene family encoding extracellular proteins (PHEPs) in P. pachyrhizi urediniospore walls.
- Selected highly expressed PHEP family members (PHEP 107, PHEP 369) as targets.
- Generated monoclonal antibodies (MAbs) against recombinant PHEP 369.
- Tested MAb sensitivity and specificity against recombinant proteins, infected plant extracts, and other soybean pathogens.
Main Results:
- Identified PHEPs, a novel family of extracellular proteins in P. pachyrhizi.
- Detected PHEPs in infected plants as early as 3 days postinfection (dpi).
- Developed specific monoclonal antibodies (MAbs 2E8E5-1 and 3G6H7-3) against PHEP 369.
Conclusions:
- PHEPs are suitable targets for early immunodiagnostic detection of ASR.
- Developed MAbs can be used in assays to detect infected soybeans and monitor ASR spore presence.
