title: The bifunctional plant receptor, OsCERK1, regulates both chitin-triggered immunity and arbuscular mycorrhizal symbiosis in rice.
abstract: Plants are constantly exposed to threats from pathogenic microbes and thus developed an innate immune system to protect themselves. On the other hand, many plants also have the ability to establish endosymbiosis with beneficial microbes such as arbuscular mycorrhizal (AM) fungi or rhizobial bacteria, which improves the growth of host plants. How plants evolved these systems managing such opposite plant-microbe interactions is unclear. We show here that knockout (KO) mutants of OsCERK1, a rice receptor kinase essential for chitin signaling, were impaired not only for chitin-triggered defense responses but also for AM symbiosis, indicating the bifunctionality of OsCERK1 in defense and symbiosis. On the other hand, a KO mutant of OsCEBiP, which forms a receptor complex with OsCERK1 and is essential for chitin-triggered immunity, established mycorrhizal symbiosis normally. Therefore, OsCERK1 but not chitin-triggered immunity is required for AM symbiosis. Furthermore, experiments with chimeric receptors showed that the kinase domains of OsCERK1 and homologs from non-leguminous, mycorrhizal plants could trigger nodulation signaling in legume-rhizobium interactions as the kinase domain of Nod factor receptor1 (NFR1), which is essential for triggering the nodulation program in leguminous plants, did. Because leguminous plants are believed to have developed the rhizobial symbiosis on the basis of AM symbiosis, our results suggest that the symbiotic function of ancestral CERK1 in AM symbiosis enabled the molecular evolution to leguminous NFR1 and resulted in the establishment of legume-rhizobia symbiosis. These results also suggest that OsCERK1 and homologs serve as a molecular switch that activates defense or symbiotic responses depending on the infecting microbes.
authors.affiliation: Department of Life Sciences, School of Agriculture, Meiji University, Kawasaki, Kanagawa, 214-8571 Japan These authors contributed equally to this work.
authors.forename: Kana
authors.initials: K
authors.lastname: Miyata
authors.affiliation: Tokyo University of Agriculture & Technology, Fuchu, Tokyo, 183-8509 Japan These authors contributed equally to this work.
authors.forename: Toshinori
authors.initials: T
authors.lastname: Kozaki
authors.affiliation: Genetically Modified Organism Research Center, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, 305-8602 Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Kouzai
authors.affiliation: Genetically Modified Organism Research Center, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, 305-8602 Japan.
authors.forename: Kenjirou
authors.initials: K
authors.lastname: Ozawa
authors.affiliation: Tokyo University of Agriculture & Technology, Fuchu, Tokyo, 183-8509 Japan.
authors.forename: Kazuo
authors.initials: K
authors.lastname: Ishii
authors.affiliation: Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8572 Japan.
authors.forename: Erika
authors.initials: E
authors.lastname: Asamizu
authors.affiliation: Faculty of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Ibaraki, 305-8572 Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Okabe
authors.affiliation: Genetically Modified Organism Research Center, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, 305-8602 Japan.
authors.forename: Yosuke
authors.initials: Y
authors.lastname: Umehara
authors.affiliation: Department of Life Sciences, School of Agriculture, Meiji University, Kawasaki, Kanagawa, 214-8571 Japan.
authors.forename: Ayano
authors.initials: A
authors.lastname: Miyamoto
authors.affiliation: Graduate School of Agricultural and Life Sciences, The University of Tokyo, Bunkyo-ku, Tokyo, 113-8657 Japan.
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Kobae
authors.affiliation: Graduate School of Life and Environmental Sciences, Osaka Prefecture University, Sakai, Osaka, 599-8531 Japan.
authors.forename: Kohki
authors.initials: K
authors.lastname: Akiyama
authors.affiliation: Department of Life Sciences, School of Agriculture, Meiji University, Kawasaki, Kanagawa, 214-8571 Japan.
authors.forename: Hanae
authors.initials: H
authors.lastname: Kaku
authors.affiliation: Genetically Modified Organism Research Center, National Institute of Agrobiological Sciences, Tsukuba, Ibaraki, 305-8602 Japan.
authors.forename: Yoko
authors.initials: Y
authors.lastname: Nishizawa
authors.affiliation: Department of Life Sciences, School of Agriculture, Meiji University, Kawasaki, Kanagawa, 214-8571 Japan tf11001@meiji.ac.jp shibuya@isc.meiji.ac.jp.
authors.forename: Naoto
authors.initials: N
authors.lastname: Shibuya
authors.affiliation: Department of Life Sciences, School of Agriculture, Meiji University, Kawasaki, Kanagawa, 214-8571 Japan tf11001@meiji.ac.jp shibuya@isc.meiji.ac.jp.
authors.forename: Tomomi
authors.initials: T
authors.lastname: Nakagawa
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D002686:Chitin / Q000276:immunology / Q000378:metabolism*; D019143:Evolution, Molecular; D018506:Gene Expression Regulation, Plant; D055786:Gene Knockout Techniques; D005816:Genetic Complementation Test; D000070116:Lotus / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation; D038821:Mycorrhizae / Q000502:physiology*; D012275:Oryza / Q000276:immunology / Q000382:microbiology / Q000502:physiology*; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D012231:Rhizobium / Q000502:physiology; D015398:Signal Transduction; D013559:Symbiosis
chemical_list: D010940:Plant Proteins; D002686:Chitin; D017346:Protein Serine-Threonine Kinases
keywords: Arbuscular mycorrhizal fungi; Defense; Lotus japonicus; Rhizobia; Rice; Symbiosis