title: The inducible nitA promoter provides a powerful molecular switch for transgene expression in Volvox carteri.
abstract: BACKGROUND
  The multicellular green alga Volvox carteri represents an attractive model system to study various aspects of multicellularity like cellular differentiation, morphogenesis, epithelial folding and ECM biogenesis. However, functional and molecular analyses of such processes require a wide array of molecular tools for genetic engineering. So far there are only a limited number of molecular tools available in Volvox.
  
  
  RESULTS
  Here, we show that the promoter of the V. carteri nitrate reductase gene (nitA) is a powerful molecular switch for induction of transgene expression. Strong expression is triggered by simply changing the nitrogen source from ammonium to nitrate. We also show that the luciferase (g-luc) gene from the marine copepod Gaussia princeps, which previously was engineered to match the codon usage of the unicellular alga Chlamydomonas reinhardtii, is a suitable reporter gene in V. carteri. Emitted light of the chemiluminescent reaction can be easily detected and quantified with a luminometer. Long-term stability of inducible expression of the chimeric nitA/g-luc transgenes after stable nuclear transformation was demonstrated by transcription analysis and bioluminescence assays.
  
  
  CONCLUSIONS
  Two novel molecular tools for genetic engineering of Volvox are now available: the nitrate-inducible nitA promoter of V. carteri and the codon-adapted luciferase reporter gene of G. princeps. These novel tools will be useful for future molecular research in V. carteri.
authors.affiliation: Department of Cellular and Developmental Biology of Plants, University of Bielefeld, Universitätsstr. 25, D-33615, Bielefeld, Germany. evdheyde@uni-bielefeld.de.
authors.forename: Eva Laura
authors.initials: EL
authors.lastname: von der Heyde
authors.affiliation: Department of Cellular and Developmental Biology of Plants, University of Bielefeld, Universitätsstr. 25, D-33615, Bielefeld, Germany. bklein@uni-bielefeld.de.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Klein
authors.affiliation: Department of Cellular and Developmental Biology of Plants, University of Bielefeld, Universitätsstr. 25, D-33615, Bielefeld, Germany. lars.abram@yahoo.de.
authors.forename: Lars
authors.initials: L
authors.lastname: Abram
authors.affiliation: Department of Cellular and Developmental Biology of Plants, University of Bielefeld, Universitätsstr. 25, D-33615, Bielefeld, Germany. armin.hallmann@gmx.de.
authors.forename: Armin
authors.initials: A
authors.lastname: Hallmann
mesh_terms: D020418:Algal Proteins / Q000235:genetics; D064751:Ammonium Compounds / Q000494:pharmacology; D000818:Animals; D033342:Copepoda / Q000201:enzymology* / Q000235:genetics; D017930:Genes, Reporter; D005818:Genetic Engineering / Q000379:methods; D008156:Luciferases / Q000235:genetics / Q000378:metabolism*; D049408:Luminescent Agents / Q000378:metabolism; D008954:Models, Biological; D050901:Nitrate Reductase / Q000235:genetics*; D009566:Nitrates / Q000494:pharmacology; D011401:Promoter Regions, Genetic / Q000187:drug effects; D019076:Transgenes; D044446:Volvox / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism
chemical_list: D020418:Algal Proteins; D064751:Ammonium Compounds; D049408:Luminescent Agents; D009566:Nitrates; D008156:Luciferases; D050901:Nitrate Reductase