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Takagi M, Hamano K, Takagi H, Morimoto T, Akimitsu K, Terauchi R, Shirasu K, Ichimura K. Disruption of the MAMP-Induced MEKK1-MKK1/MKK2-MPK4 Pathway Activates the TNL Immune Receptor SMN1/RPS6. Plant Cell Physiol 2019; 60:778-787. [PMID: 30590768 DOI: 10.1093/pcp/pcy243] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Accepted: 12/20/2018] [Indexed: 06/09/2023]
Abstract
Mitogen-activated protein kinase (MAPK) pathways have a pivotal role in innate immunity signaling in plants. In Arabidopsis, the MAPK pathway that consists of MEKK1, MKK1/MKK2 and MPK4 is involved in pattern-triggered immunity signaling upstream of defense gene expression. This pathway is partly guarded by SUMM2, a nucleotide-binding domain leucine-rich repeat (NLR) protein, which is activated by disruption of the MAPK pathway. To identify other components required for the guard mechanism, here we developed a new mutant screening system utilizing a dwarf autoimmune line that overexpressed the N-terminal regulatory domain of MEKK1. Mutants with suppression of the dwarf, autoimmune phenotypes were identified, and one locus responsible for the phenotype was designated as suppressor of MEKK1N overexpression-induced dwarf 1 (SMN1). MutMap analysis revealed that SMN1 encodes the Toll/Interleukin-1 receptor (TIR)-class NLR protein RPS6, a previously identified resistant protein against bacterial pathogen Pseudomonas syringae pv. tomato expressing the HopA1 effector. Importantly, mutations in SMN1/RPS6 also partially suppressed the dwarf, autoimmune phenotypes of mekk1 and mpk4 plants. Our results suggest that the two structurally distinct NLR proteins, SMN1/RPS6 and SUMM2, monitor integrity of the MEKK1-MKK1/MKK2-MPK4 pathway.
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Affiliation(s)
- Momoko Takagi
- Faculty and Graduate School of Agriculture, Kagawa University, 2393 Ikenobe, Miki-cho, Kita-gun, Kagawa, Japan
- United Graduate School of Agriculture, Ehime University, 3-5-7 Tarumi, Matsuyama, Ehime, Japan
| | - Kohei Hamano
- Faculty and Graduate School of Agriculture, Kagawa University, 2393 Ikenobe, Miki-cho, Kita-gun, Kagawa, Japan
| | - Hiroki Takagi
- Department of Genomics and Breeding, Iwate Biotechnology Research Center, 22-174-4 Narita, Kitakami, Iwate, Japan
- Department of Bioproduction Science, Ishikawa Prefectural University, 1-308 Suematsu, Nonoichi, Ishikawa, Japan
| | - Takayuki Morimoto
- Faculty and Graduate School of Agriculture, Kagawa University, 2393 Ikenobe, Miki-cho, Kita-gun, Kagawa, Japan
| | - Kazuya Akimitsu
- Faculty and Graduate School of Agriculture, Kagawa University, 2393 Ikenobe, Miki-cho, Kita-gun, Kagawa, Japan
- United Graduate School of Agriculture, Ehime University, 3-5-7 Tarumi, Matsuyama, Ehime, Japan
| | - Ryohei Terauchi
- Department of Genomics and Breeding, Iwate Biotechnology Research Center, 22-174-4 Narita, Kitakami, Iwate, Japan
- Laboratory of Crop Evolution, Graduate School of Agricultural Sciences, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, Japan
| | - Ken Shirasu
- RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku Yokohama, Kanagawa, Japan
| | - Kazuya Ichimura
- Faculty and Graduate School of Agriculture, Kagawa University, 2393 Ikenobe, Miki-cho, Kita-gun, Kagawa, Japan
- United Graduate School of Agriculture, Ehime University, 3-5-7 Tarumi, Matsuyama, Ehime, Japan
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