title: The deubiquitinating enzyme AMSH1 is required for rhizobial infection and nodule organogenesis in Lotus japonicus.
abstract: Legume-rhizobium symbiosis contributes large quantities of fixed nitrogen to both agricultural and natural ecosystems. This global impact and the selective interaction between rhizobia and legumes culminating in development of functional root nodules have prompted detailed studies of the underlying mechanisms. We performed a screen for aberrant nodulation phenotypes using the Lotus japonicus LORE1 insertion mutant collection. Here, we describe the identification of amsh1 mutants that only develop small nodule primordia and display stunted shoot growth, and show that the aberrant nodulation phenotype caused by LORE1 insertions in the Amsh1 gene may be separated from the shoot phenotype. In amsh1 mutants, rhizobia initially became entrapped in infection threads with thickened cells walls. Some rhizobia were released into plant cells much later than observed for the wild-type; however, no typical symbiosome structures were formed. Furthermore, cytokinin treatment only very weakly induced nodule organogenesis in amsh1 mutants, suggesting that AMSH1 function is required downstream of cytokinin signaling. Biochemical analysis showed that AMSH1 is an active deubiquitinating enzyme, and that AMSH1 specifically cleaves K63-linked ubiquitin chains. Post-translational ubiquitination and deubiquitination processes involving the AMSH1 deubiquitinating enzyme are thus involved in both infection and organogenesis in Lotus japonicus.
authors.affiliation: Centre for Carbohydrate Recognition and Signalling, Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10, DK-8000, Aarhus C, Denmark.
authors.forename: Anna
authors.initials: A
authors.lastname: Małolepszy
authors.affiliation: Centre for Carbohydrate Recognition and Signalling, Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10, DK-8000, Aarhus C, Denmark.
authors.forename: Dorian Fabian
authors.initials: DF
authors.lastname: Urbański
authors.affiliation: The James Hutton Institute, Invergowrie, Dundee, DD2 5DA, UK.
authors.forename: Euan K
authors.initials: EK
authors.lastname: James
authors.affiliation: Centre for Carbohydrate Recognition and Signalling, Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10, DK-8000, Aarhus C, Denmark.
authors.forename: Niels
authors.initials: N
authors.lastname: Sandal
authors.affiliation: Department of Plant Systems Biology, Technische Universität München, D-85354, Freising, Germany.
authors.forename: Erika
authors.initials: E
authors.lastname: Isono
authors.affiliation: Centre for Carbohydrate Recognition and Signalling, Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10, DK-8000, Aarhus C, Denmark.
authors.forename: Jens
authors.initials: J
authors.lastname: Stougaard
authors.affiliation: Centre for Carbohydrate Recognition and Signalling, Department of Molecular Biology and Genetics, Aarhus University, Gustav Wieds Vej 10, DK-8000, Aarhus C, Denmark.
authors.forename: Stig Uggerhøj
authors.initials: SU
authors.lastname: Andersen
mesh_terms: D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D018506:Gene Expression Regulation, Plant; D000070116:Lotus / Q000201:enzymology* / Q000382:microbiology* / Q000502:physiology; D008969:Molecular Sequence Data; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D012231:Rhizobium / Q000472:pathogenicity*; D053204:Root Nodules, Plant / Q000378:metabolism* / Q000382:microbiology*; D013559:Symbiosis / Q000502:physiology; D064570:Ubiquitin-Specific Proteases / Q000235:genetics / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D029681:Arabidopsis Proteins; D010940:Plant Proteins; D064570:Ubiquitin-Specific Proteases; C586775:AMSH1 protein, Arabidopsis
keywords: AMSH1; LORE1; Lotus japonicus; deubiquitination; nodulation mutant; symbiosis