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ARS Home » Northeast Area » Frederick, Maryland » Foreign Disease-Weed Science Research » Research » Publications at this Location » Publication #405645

Research Project: Integrative Genomic and Biological Approaches to Detect and Manage Emerging Foreign Fungal Plant Pathogens

Location: Foreign Disease-Weed Science Research

Title: A soybean rust effector protease suppresses host immunity and cleaves a 3-deoxy-7-phosphoheptulonate synthase

item SARTOR CHICOWSKI, ALINE - Iowa State University
item QI, MINGSHENG - Iowa State University
item VARIZ, HARIS - Iowa State University
item BREDOW, MELISSA - Iowa State University
item MONTES, CHRISTIAN - Iowa State University
item CAIAZZA, FRANCESCO - University Of California San Francisco (UCSF)
item DONG, HAILI - Iowa State University
item MARGETS, ALEXANDRA - Indiana University
item MEJIAS, JOFFREY - University Of Montpellier
item WALLEY, JUSTIN - Iowa State University
item CRAIK, CHARLES - University Of California San Francisco (UCSF)
item Pedley, Kerry
item AUNG, KYAW - Iowa State University
item INNES, ROGER - Indiana University
item WHITHAM, STEVEN - Iowa State University

Submitted to: bioRxiv
Publication Type: Pre-print Publication
Publication Acceptance Date: 9/8/2023
Publication Date: 9/8/2023
Citation: Sartor Chicowski, A., Qi, M., Montes, C., Variz, H., Caiazza, F., Bredow, M., Dong, H., Margets, A., Walley, J., Aung, K., Craik, C.S., Pedley, K.F., Innes, R., Whitham, S.A. 2023. A soybean rust effector protease suppresses host immunity and cleaves a 3-deoxy-7-phosphoheptulonate synthase. bioRxiv.

Interpretive Summary: Soybean rust is a devastating disease of soybeans that can lead to crop yield losses as high as 90%. There are currently no soybean cultivars available that are fully resistant to this disease. Therefore, we analyzed a soybean rust protein called PpEC15 to better understand the disease. Our data show that PpEC15 suppresses plant disease defense responses. PpEC15 was found in all soybean rust samples analyzed, and in many other fungi that cause rust disease in other plants. Understanding the role of proteins such as PpEC15 will help scientists and plant breeders to develop soybeans with durable resistance to soybean rust.

Technical Abstract: The devastating soybean rust (SBR) pathogen, Phakopsora pachyrhizi, encodes many secreted proteins, but only two have been functionally characterized for their roles in rust virulence. Here, we demonstrate that transient expression of P. pachyrhizi effector candidate 15 (PpEC15), an aspartic protease, leads to enhanced bacterial growth in planta, suppression of callose deposition, reduced expression of plant defense-related marker genes and suppression of pathogen-associated molecular pattern (PAMP)-induced reactive oxygen species (ROS). Stable expression of PpEC15 in soybean suppresses PAMP-induced ROS production and enhances bacterial growth, indicating that, collectively, PpEC15 suppresses host and non-host innate immune responses. Yeast-two-hybrid and proximity labeling identified putative PpEC15 interacting partners including a peptide-chain release factor (PCRF), a NAC83 (NAM, ATAF, and CUC) transcription factor, and a DAHP (3-deoxy-7-phosphoheptulonate) synthase. We further show that PpEC15 can cleave DAHP but does not cleave PCRF or NAC83. Virus-induced gene silencing of NAC83, PCRF and DAHP altered PAMP-induced ROS production and salicylic acid production, indicating that these proteins may be involved in immune signaling. Collectively, our data show that PpEC15 is conserved across P. pachyrhizi isolates and other economically important rust species and is involved in the suppression of plant basal defense responses. Understanding the role of PpEC15 in P. pachyrhizi virulence will provide a foundation for designing targeted intervention strategies to generate rust-resistant crops.