title: A dual system formed by the ARC and NR molybdoenzymes mediates nitrite-dependent NO production in Chlamydomonas.
abstract: Nitric oxide (NO) is a relevant signal molecule involved in many plant processes. However, the mechanisms and proteins responsible for its synthesis are scarcely known. In most photosynthetic organisms NO synthases have not been identified, and Nitrate Reductase (NR) has been proposed as the main enzymatic NO source, a process that in vitro is also catalysed by other molybdoenzymes. By studying transcriptional regulation, enzyme approaches, activity assays with in vitro purified proteins and in vivo and in vitro NO determinations, we have addressed the role of NR and Amidoxime Reducing Component (ARC) in the NO synthesis process. N\R and ARC were intimately related both at transcriptional and activity level. Thus, arc mutants showed high NIA1 (NR gene) expression and NR activity. Conversely, mutants without active NR displayed an increased ARC expression in nitrite medium. Our results with nia1 and arc mutants and with purified enzymes support that ARC catalyses the NO production from nitrite taking electrons from NR and not from Cytb5-1/Cytb5-Reductase, the component partners previously described for ARC (proposed as NOFNiR, Nitric Oxide-Forming Nitrite Reductase). This NR-ARC dual system would be able to produce NO in the presence of nitrate, condition under which NR is unable to do it.
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Córdoba, Campus de Rabanales, Campus de excelencia internacional (CeiA3), Edif. Severo Ochoa, Córdoba, 14071, Spain.
authors.forename: Alejandro
authors.initials: A
authors.lastname: Chamizo-Ampudia
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Córdoba, Campus de Rabanales, Campus de excelencia internacional (CeiA3), Edif. Severo Ochoa, Córdoba, 14071, Spain.
authors.forename: Emanuel
authors.initials: E
authors.lastname: Sanz-Luque
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Córdoba, Campus de Rabanales, Campus de excelencia internacional (CeiA3), Edif. Severo Ochoa, Córdoba, 14071, Spain.
authors.forename: Ángel
authors.initials: Á
authors.lastname: Llamas
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Córdoba, Campus de Rabanales, Campus de excelencia internacional (CeiA3), Edif. Severo Ochoa, Córdoba, 14071, Spain.
authors.forename: Francisco
authors.initials: F
authors.lastname: Ocaña-Calahorro
authors.affiliation: Institute of Plant Biochemistry and Photosynthesis, C.S.I.C. and University of Sevilla, Américo Vespucio 49, Sevilla, 41092, Spain.
authors.forename: Vicente
authors.initials: V
authors.lastname: Mariscal
authors.affiliation: Group of Biochemistry and Cell Signaling in Nitric Oxide. Department of Biochemistry and Molecular Biology, Campus 'Las Lagunillas', E-23071, University of Jaén, Jaén, Spain.
authors.forename: Alfonso
authors.initials: A
authors.lastname: Carreras
authors.affiliation: Group of Biochemistry and Cell Signaling in Nitric Oxide. Department of Biochemistry and Molecular Biology, Campus 'Las Lagunillas', E-23071, University of Jaén, Jaén, Spain.
authors.forename: Juan B
authors.initials: JB
authors.lastname: Barroso
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Córdoba, Campus de Rabanales, Campus de excelencia internacional (CeiA3), Edif. Severo Ochoa, Córdoba, 14071, Spain.
authors.forename: Aurora
authors.initials: A
authors.lastname: Galván
authors.affiliation: Department of Biochemistry and Molecular Biology, University of Córdoba, Campus de Rabanales, Campus de excelencia internacional (CeiA3), Edif. Severo Ochoa, Córdoba, 14071, Spain. bb1feree@uco.es.
authors.forename: Emilio
authors.initials: E
authors.lastname: Fernández
mesh_terms: D053898:Biosynthetic Pathways; D016825:Chlamydomonas reinhardtii / Q000378:metabolism*; D008954:Models, Biological; D050901:Nitrate Reductase / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D009569:Nitric Oxide / Q000096:biosynthesis*; D009573:Nitrites / Q000378:metabolism; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*
chemical_list: D009573:Nitrites; D010940:Plant Proteins; D009569:Nitric Oxide; D050901:Nitrate Reductase
keywords: ARC; Chlamydomonas; NR; molybdenum; multidomain proteins; nitric oxide; nitrite