Nitric oxide synthesis by nitrate reductase is regulated during development in Aspergillus.
Nitric oxide (NO) is a signalling molecule involved in many biological processes in bacteria, plants and mammals. However, little is known about the role and biosynthesis of NO in fungi. Here we show that NO production is increased at the early stages of the transition from vegetative growth to development in Aspergillus nidulans. Full NO production requires a functional nitrate reductase (NR) gene (niaD) that is upregulated upon induction of conidiation, even under N-repressing conditions in the presence of ammonium. At this stage, NO homeostasis is achieved by balancing biosynthesis (NR) and catabolism (flavohaemoglobins). niaD and flavohaemoglobin fhbA are transiently upregulated upon induction of conidiation, and both regulators AreA and NirA are necessary for this transcriptional response. The second flavohaemoglobin gene fhbB shows a different expression profile being moderately expressed during the early stages of the transition phase from vegetative growth to conidiation, but it is strongly induced 24 h later. NO levels influence the balance between conidiation and sexual reproduction because artificial strong elevation of NO levels reduced conidiation and induced the formation of cleistothecia. The nitrate-independent and nitrogen metabolite repression-insensitive transcriptional upregulation of niaD during conidiation suggests a novel role for NR in linking metabolism and development.
Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
Ana T
AT
Marcos
Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
María S
MS
Ramos
Department of Food Science, Institute of Agrochemistry and Food Technology (IATA), Valencia, Spain.
Jose F
JF
Marcos
Department of Food Science, Institute of Agrochemistry and Food Technology (IATA), Valencia, Spain.
Lourdes
L
Carmona
Fungal Genetics and Genomics Unit, Department of Applied Genetics and Cell Biology, University of Natural Resources and Life Sciences (BOKU) Vienna, Vienna, Austria.|Department of Health and Environment, Bioresources, Austrian Institute of Technology (AIT), Vienna, Austria.
Joseph
J
Strauss
Departamento de Genética, Facultad de Biología, Universidad de Sevilla, Sevilla, Spain.
David
http://orcid.org/0000-0002-7293-7332
D
Cánovas
D001233:Aspergillus nidulans / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D015966:Gene Expression Regulation, Fungal; D050901:Nitrate Reductase / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism*; D013172:Spores, Fungal / Q000254:growth & development; D014158:Transcription, Genetic
D009569:Nitric Oxide; D050901:Nitrate Reductase