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Takagi M, Iwamoto N, Kubo Y, Morimoto T, Takagi H, Takahashi F, Nishiuchi T, Tanaka K, Taji T, Kaminaka H, Shinozaki K, Akimitsu K, Terauchi R, Shirasu K, Ichimura K. Arabidopsis SMN2/HEN2, Encoding DEAD-Box RNA Helicase, Governs Proper Expression of the Resistance Gene SMN1/RPS6 and Is Involved in Dwarf, Autoimmune Phenotypes of mekk1 and mpk4 Mutants. Plant Cell Physiol 2020; 61:1507-1516. [PMID: 32467981 DOI: 10.1093/pcp/pcaa071] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [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: 04/29/2020] [Accepted: 05/21/2020] [Indexed: 06/11/2023]
Abstract
In Arabidopsis thaliana, a mitogen-activated protein kinase pathway, MEKK1-MKK1/MKK2-MPK4, is important for basal resistance and disruption of this pathway results in dwarf, autoimmune phenotypes. To elucidate the complex mechanisms activated by the disruption of this pathway, we have previously developed a mutant screening system based on a dwarf autoimmune line that overexpressed the N-terminal regulatory domain of MEKK1. Here, we report that the second group of mutants, smn2, had defects in the SMN2 gene, encoding a DEAD-box RNA helicase. SMN2 is identical to HEN2, whose function is vital for the nuclear RNA exosome because it provides non-ribosomal RNA specificity for RNA turnover, RNA quality control and RNA processing. Aberrant SMN1/RPS6 transcripts were detected in smn2 and hen2 mutants. Disease resistance against Pseudomonas syringae pv. tomato DC3000 (hopA1), which is conferred by SMN1/RPS6, was decreased in smn2 mutants, suggesting a functional connection between SMN1/RPS6 and SMN2/HEN2. We produced double mutants mekk1smn2 and mpk4smn2 to determine whether the smn2 mutations suppress the dwarf, autoimmune phenotypes of the mekk1 and mpk4 mutants, as the smn1 mutations do. As expected, the mekk1 and mpk4 phenotypes were suppressed by the smn2 mutations. These results suggested that SMN2 is involved in the proper function of SMN1/RPS6. The Gene Ontology enrichment analysis using RNA-seq data showed that defense genes were downregulated in smn2, suggesting a positive contribution of SMN2 to the genome-wide expression of defense genes. In conclusion, this study provides novel insight into plant immunity via SMN2/HEN2, an essential component of the nuclear RNA exosome.
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Affiliation(s)
- Momoko Takagi
- Faculty and Graduate School of Agriculture, Kagawa University, 2393 Ikenobe, Miki-cho, Kita-gun, Kagawa, 761-0795 Japan
- United Graduate School of Agriculture, Ehime University, 3-5-7 Tarumi, Matsuyama, Ehime, 790-8566 Japan
- Faculty of Agriculture, Tottori University, 4-101 Koyama Minami, Tottori, 680-8553 Japan
| | - Naoki Iwamoto
- Faculty and Graduate School of Agriculture, Kagawa University, 2393 Ikenobe, Miki-cho, Kita-gun, Kagawa, 761-0795 Japan
| | - Yuta Kubo
- Faculty and Graduate School of Agriculture, Kagawa University, 2393 Ikenobe, Miki-cho, Kita-gun, Kagawa, 761-0795 Japan
| | - Takayuki Morimoto
- Faculty and Graduate School of Agriculture, Kagawa University, 2393 Ikenobe, Miki-cho, Kita-gun, Kagawa, 761-0795 Japan
| | - Hiroki Takagi
- Department of Genomics and Breeding, Iwate Biotechnology Research Center, 22-174-4 Narita, Kitakami, Iwate, 024-0003 Japan
- Department of Bioproduction Science, Ishikawa Prefectural University, 1-308 Suematsu, Nonoichi, Ishikawa, 921-8836 Japan
| | - Fuminori Takahashi
- Gene Discovery Research Group, RIKEN Center for Sustainable Resource Science, 3-1-1 Koyadai, Tsukuba, Ibaraki, 305-0074 Japan
| | - Takumi Nishiuchi
- Institute for Gene Research, Advanced Science Research Center, Kanazawa University, Takaramachi, Kanazawa, Ishikawa, 920-8640 Japan
| | - Keisuke Tanaka
- Nodai Genome Research Center, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo, 156-8502 Japan
| | - Teruaki Taji
- Department of Bioscience, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo, 156-8502 Japan
| | - Hironori Kaminaka
- Faculty of Agriculture, Tottori University, 4-101 Koyama Minami, Tottori, 680-8553 Japan
| | - Kazuo Shinozaki
- Gene Discovery Research Group, RIKEN Center for Sustainable Resource Science, 3-1-1 Koyadai, Tsukuba, Ibaraki, 305-0074 Japan
| | - Kazuya Akimitsu
- Faculty and Graduate School of Agriculture, Kagawa University, 2393 Ikenobe, Miki-cho, Kita-gun, Kagawa, 761-0795 Japan
- United Graduate School of Agriculture, Ehime University, 3-5-7 Tarumi, Matsuyama, Ehime, 790-8566 Japan
| | - Ryohei Terauchi
- Department of Genomics and Breeding, Iwate Biotechnology Research Center, 22-174-4 Narita, Kitakami, Iwate, 024-0003 Japan
- Laboratory of Crop Evolution, Graduate School of Agricultural Sciences, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto, 606-8502 Japan
| | - Ken Shirasu
- Plant Immunity Research Group, RIKEN Center for Sustainable Resource Science, 1-7-22 Suehiro-cho, Tsurumi-ku, Yokohama, Kanagawa, 230-0045 Japan
| | - Kazuya Ichimura
- Faculty and Graduate School of Agriculture, Kagawa University, 2393 Ikenobe, Miki-cho, Kita-gun, Kagawa, 761-0795 Japan
- United Graduate School of Agriculture, Ehime University, 3-5-7 Tarumi, Matsuyama, Ehime, 790-8566 Japan
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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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