Suppression or Activation of Immune Responses by Predicted Secreted Proteins of the Soybean Rust Pathogen Phakopsora pachyrhizi

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Qi, Mingsheng
Grayczyk, James
Seitz, Janina
Lee, Youngsill
Link, Tobias
Choi, Doil
Pedley, Kerry
Voegele, Ralf
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Whitham, Steven
Assistant Professor
Baum, Thomas
Distinguished Professor
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Plant Pathology and Microbiology
The Department of Plant Pathology and Microbiology and the Department of Entomology officially merged as of September 1, 2022. The new department is known as the Department of Plant Pathology, Entomology, and Microbiology (PPEM). The overall mission of the Department is to benefit society through research, teaching, and extension activities that improve pest management and prevent disease. Collectively, the Department consists of about 100 faculty, staff, and students who are engaged in research, teaching, and extension activities that are central to the mission of the College of Agriculture and Life Sciences. The Department possesses state-of-the-art research and teaching facilities in the Advanced Research and Teaching Building and in Science II. In addition, research and extension activities are performed off-campus at the Field Extension Education Laboratory, the Horticulture Station, the Agriculture Engineering/Agronomy Farm, and several Research and Demonstration Farms located around the state. Furthermore, the Department houses the Plant and Insect Diagnostic Clinic, the Iowa Soybean Research Center, the Insect Zoo, and BugGuide. Several USDA-ARS scientists are also affiliated with the Department.
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Rust fungi, such as the soybean rust pathogen Phakopsora pachyrhizi, are major threats to crop production. They form specialized haustoria that are hyphal structures intimately associated with host-plant cell membranes. These haustoria have roles in acquiring nutrients and secreting effector proteins that manipulate host immune systems. Functional characterization of effector proteins of rust fungi is important for understanding mechanisms that underlie their virulence and pathogenicity. Hundreds of candidate effector proteins have been predicted for rust pathogens, but it is not clear how to prioritize these effector candidates for further characterization. There is a need for high-throughput approaches for screening effector candidates to obtain experimental evidence for effector-like functions, such as the manipulation of host immune systems. We have focused on identifying effector candidates with immune-related functions in the soybean rust fungus P. pachyrhizi. To facilitate the screening of many P. pachyrhizi effector candidates (named PpECs), we used heterologous expression systems, including the bacterial type III secretion system, Agrobacterium infiltration, a plant virus, and a yeast strain, to establish an experimental pipeline for identifying PpECs with immune-related functions and establishing their subcellular localizations. Several PpECs were identified that could suppress or activate immune responses in nonhost Nicotiana benthamiana, N. tabacum, Arabidopsis, tomato, or pepper plants.


This article is published as Qi, Mingsheng, James P. Grayczyk, Janina M. Seitz, Youngsill Lee, Tobias I. Link, Doil Choi, Kerry F. Pedley, Ralf T. Voegele, Thomas J. Baum, and Steven A. Whitham. "Suppression or activation of immune responses by predicted secreted proteins of the soybean rust pathogen Phakopsora pachyrhizi." Molecular plant-microbe interactions 31, no. 1 (2017): 163-174. doi: 10.1094/MPMI-07-17-0173-FI.