title: From defense to symbiosis: limited alterations in the kinase domain of LysM receptor-like kinases are crucial for evolution of legume-Rhizobium symbiosis.
abstract: Nitrogen-fixing symbiosis between legumes and rhizobia is initiated by the recognition of rhizobial Nod factors (NFs) by host plants. NFs are diversely modified derivatives of chitin oligosaccharide, a fungal elicitor that induces defense responses in plants. Recent evidence has shown that both NFs and chitin elicitors are recognized by structurally related LysM receptor kinases. Transcriptome analyses of Lotus japonicus roots indicated that NFs not only activate symbiosis genes but also transiently activate defense-related genes through NF receptors. Conversely, chitin oligosaccharides were able to activate symbiosis genes independently of NF receptors. Analyses using chimeric genes consisting of the LysM receptor domain of a Lotus japonicus NF receptor, NFR1, and the kinase domain of an Arabidopsis chitin receptor, CERK1, demonstrated that substitution of a portion of the αEF helix in CERK1 with the amino acid sequence YAQ from the corresponding region of NFR1 enables L. japonicus nfr1 mutants to establish symbiosis with Mesorhizobium loti. We also showed that the kinase domains of two Lotus japonicus LysM receptor kinases, Lys6 and Lys7, which also possess the YAQ sequence, suppress the symbiotic defect of nfr1. These results strongly suggest that, in addition to adaptation of extracellular LysM domains to NFs, limited alterations in the kinase domain of chitin receptors have played a crucial role in shifting the intracellular signaling to symbiosis from defense responses, thus constituting one of the key genetic events in the evolution of root nodule symbiosis in legume plants.
authors.affiliation: Division of Plant Sciences, National Institute of Agrobiological Sciences, Tsukuba 305-8602, Japan. ntomomi@affrc.go.jp
authors.forename: Tomomi
authors.initials: T
authors.lastname: Nakagawa
authors.forename: Hanae
authors.initials: H
authors.lastname: Kaku
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Shimoda
authors.forename: Akifumi
authors.initials: A
authors.lastname: Sugiyama
authors.forename: Masayuki
authors.initials: M
authors.lastname: Shimamura
authors.forename: Kojiro
authors.initials: K
authors.lastname: Takanashi
authors.forename: Kazufumi
authors.initials: K
authors.lastname: Yazaki
authors.forename: Toshio
authors.initials: T
authors.lastname: Aoki
authors.forename: Naoto
authors.initials: N
authors.lastname: Shibuya
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Kouchi
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D017360:Arabidopsis / Q000235:genetics; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002686:Chitin / Q000378:metabolism; D019143:Evolution, Molecular; D020869:Gene Expression Profiling; D018506:Gene Expression Regulation, Plant / Q000502:physiology; D005816:Genetic Complementation Test; D008070:Lipopolysaccharides / Q000378:metabolism; D000070116:Lotus / Q000201:enzymology* / Q000235:genetics / Q000382:microbiology; D059128:Mesorhizobium / Q000235:genetics / Q000502:physiology*; D008969:Molecular Sequence Data; D009586:Nitrogen Fixation / Q000502:physiology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D030821:Plants, Genetically Modified; D011494:Protein Kinases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D017434:Protein Structure, Tertiary; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D053204:Root Nodules, Plant / Q000166:cytology / Q000378:metabolism / Q000382:microbiology*; D016415:Sequence Alignment; D015398:Signal Transduction; D013559:Symbiosis / Q000235:genetics / Q000502:physiology*
chemical_list: D029681:Arabidopsis Proteins; D008070:Lipopolysaccharides; D010940:Plant Proteins; D011956:Receptors, Cell Surface; D002686:Chitin; D011494:Protein Kinases; C525882:CERK1 protein, Arabidopsis; D017346:Protein Serine-Threonine Kinases