title: A CCaMK-CYCLOPS-DELLA Complex Activates Transcription of RAM1 to Regulate Arbuscule Branching.
abstract: Intracellular arbuscular mycorrhiza symbiosis between plants and glomeromycotan fungi leads to formation of highly branched fungal arbuscules that release mineral nutrients to the plant host. Their development is regulated in plants by a mechanistically unresolved interplay between symbiosis, nutrient, and hormone (gibberellin) signaling. Using a positional cloning strategy and a retrotransposon insertion line, we identify two novel alleles of Lotus japonicus REDUCED ARBUSCULAR MYCORRHIZA1 (RAM1) encoding a GRAS protein. We confirm that RAM1 is a central regulator of arbuscule development: arbuscule branching is arrested in L. japonicus ram1 mutants, and ectopic expression of RAM1 activates genes critical for arbuscule development in the absence of fungal symbionts. Epistasis analysis places RAM1 downstream of CCaMK, CYCLOPS, and DELLA because ectopic expression of RAM1 restores arbuscule formation in cyclops mutants and in the presence of suppressive gibberellin. The corresponding proteins form a complex that activates RAM1 expression via binding of CYCLOPS to a cis element in the RAM1 promoter. We thus reveal a transcriptional cascade in arbuscule development that employs the promoter of RAM1 as integrator of symbiotic (transmitted via CCaMK and CYCLOPS) and hormonal (gibberellin) signals.
authors.affiliation: Faculty of Biology, Genetics, Biocenter Martinsried, LMU Munich, Großhaderner Strasse 2-4, 82152 Martinsried, Germany.
authors.forename: Priya
authors.initials: P
authors.lastname: Pimprikar
authors.affiliation: Faculty of Biology, Genetics, Biocenter Martinsried, LMU Munich, Großhaderner Strasse 2-4, 82152 Martinsried, Germany.
authors.forename: Samy
authors.initials: S
authors.lastname: Carbonnel
authors.affiliation: Faculty of Biology, Genetics, Biocenter Martinsried, LMU Munich, Großhaderner Strasse 2-4, 82152 Martinsried, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Paries
authors.affiliation: Faculty of Biology, Genetics, Biocenter Martinsried, LMU Munich, Großhaderner Strasse 2-4, 82152 Martinsried, Germany.
authors.forename: Katja
authors.initials: K
authors.lastname: Katzer
authors.affiliation: Faculty of Biology, Genetics, Biocenter Martinsried, LMU Munich, Großhaderner Strasse 2-4, 82152 Martinsried, Germany.
authors.forename: Verena
authors.initials: V
authors.lastname: Klingl
authors.affiliation: Faculty of Biology, Genetics, Biocenter Martinsried, LMU Munich, Großhaderner Strasse 2-4, 82152 Martinsried, Germany.
authors.forename: Monica J
authors.initials: MJ
authors.lastname: Bohmer
authors.affiliation: Faculty of Biology, Genetics, Biocenter Martinsried, LMU Munich, Großhaderner Strasse 2-4, 82152 Martinsried, Germany.
authors.forename: Leonhard
authors.initials: L
authors.lastname: Karl
authors.affiliation: Boyce Thompson Institute for Plant Research, 533 Tower Road, Ithaca, NY 14853, USA.
authors.forename: Daniela S
authors.initials: DS
authors.lastname: Floss
authors.affiliation: Boyce Thompson Institute for Plant Research, 533 Tower Road, Ithaca, NY 14853, USA.
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Harrison
authors.affiliation: Faculty of Biology, Genetics, Biocenter Martinsried, LMU Munich, Großhaderner Strasse 2-4, 82152 Martinsried, Germany.
authors.forename: Martin
authors.initials: M
authors.lastname: Parniske
authors.affiliation: Faculty of Biology, Genetics, Biocenter Martinsried, LMU Munich, Großhaderner Strasse 2-4, 82152 Martinsried, Germany. Electronic address: caroline.gutjahr@lmu.de.
authors.forename: Caroline
authors.initials: C
authors.lastname: Gutjahr
mesh_terms: D018506:Gene Expression Regulation, Plant; D005875:Gibberellins; D000070116:Lotus / Q000235:genetics / Q000382:microbiology* / Q000502:physiology*; D038821:Mycorrhizae / Q000235:genetics / Q000502:physiology*; D010937:Plant Growth Regulators / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D015398:Signal Transduction; D013559:Symbiosis
chemical_list: D005875:Gibberellins; D010937:Plant Growth Regulators; D010940:Plant Proteins