Abstract
The Pseudomonas syringae DC3000 type III effector HopAM1 suppresses plant immunity and contains a Toll/interleukin-1 receptor (TIR) domain homologous to immunity-related TIR domains of plant nucleotide-binding leucine-rich repeat receptors that hydrolyze nicotinamide adenine dinucleotide (NAD+) and activate immunity. In vitro and in vivo assays were conducted to determine if HopAM1 hydrolyzes NAD+ and if the activity is essential for HopAM1’s suppression of plant immunity and contribution to virulence. HPLC and LC-MS were utilized to analyze metabolites produced from NAD+ by HopAM1 in vitro and in both yeast and plants. Agrobacterium-mediated transient expression and in planta inoculation assays were performed to determine HopAM1’s intrinsic enzymatic activity and virulence contribution. HopAM1 is catalytically active and hydrolyzes NAD+ to produce nicotinamide and a novel cADPR variant (v2-cADPR). Expression of HopAM1 triggers cell death in yeast and plants dependent on the putative catalytic residue glutamic acid 191 (E191) within the TIR domain. Furthermore, HopAM1’s E191 residue is required to suppress both pattern-triggered immunity and effector-triggered immunity and promote P. syringae virulence. HopAM1 manipulates endogenous NAD+ to produce v2-cADPR and promote pathogenesis. This work suggests that HopAM1’s TIR domain possesses different catalytic specificity than other TIR domain-containing NAD+ hydrolases and that pathogens exploit this activity to sabotage NAD+ metabolism for immune suppression and virulence.
| Original language | English (US) |
|---|---|
| Pages (from-to) | 890-904 |
| Number of pages | 15 |
| Journal | New Phytologist |
| Volume | 233 |
| Issue number | 2 |
| DOIs | |
| State | Published - Jan 2022 |
Bibliographical note
Funding Information:This project was partially supported through funds provided by the Nebraska Soybean Board project no. 1734, and the Center for Plant Science Innovation, University of Nebraska‐Lincoln. We are indebted to Drs Rich Wilson, Lirong Zeng and Guangyong Li for their critical reviews of the manuscript. We thank Dr Kurt Wulser from UNL’s department of chemistry for performing LC‐MS analysis. We thank the UNL microscopy core facility and the Center for Biotechnology for the use of their facilities. We thank Drs Sheng Yang He and André C. Velásquez for sharing Arabidopsis accession Xan‐2 and Xan‐5 seeds.
Funding Information:
This project was partially supported through funds provided by the Nebraska Soybean Board project no. 1734, and the Center for Plant Science Innovation, University of Nebraska-Lincoln. We are indebted to Drs Rich Wilson, Lirong Zeng and Guangyong Li for their critical reviews of the manuscript. We thank Dr Kurt Wulser from UNL?s department of chemistry for performing LC-MS analysis. We thank the UNL microscopy core facility and the Center for Biotechnology for the use of their facilities. We thank Drs Sheng Yang He and Andr? C. Vel?squez for sharing Arabidopsis accession Xan-2 and Xan-5 seeds.
Publisher Copyright:
© 2021 The Authors. New Phytologist © 2021 New Phytologist Foundation
Keywords
- HopAM1
- NAD
- NAD hydrolase
- Pseudomonas syringae
- TIR domain
- cADPR variant
- v-cADPR
- v2-cADPR
PubMed: MeSH publication types
- Journal Article
- Research Support, Non-U.S. Gov't