Targeted disruption of the NIT8 gene in Chlamydomonas reinhardtii.
We have used homologous recombination to disrupt the nuclear gene NIT8 in Chlamydomonas reinhardtii. This is the first report of targeted gene disruption of an endogenous locus in C. reinhardtii and only the second for a photosynthetic eukaryote. NIT8 encodes a protein necessary for nitrate and nitrite assimilation by C. reinhardtii. A disruption vector was constructed by placing the CRY1-1 selectable marker gene, which confers emetine resistance, within the NIT8 coding region. nit8 mutants are unable to grow on nitrate as their sole nitrogen source (Nit-) and are resistant to killing by chlorate. One of 2,000 transformants obtained after selection on emetine-chlorate medium contained a homologous insertion of five copies of the disruption plasmid into the NIT8 gene, producing an emetine-resistant, chlorate-resistant Nit- phenotype. The mutant phenotype was rescued by the wild-type NIT8 gene upon transformation. Seven other mutations at the nit8 locus, presumably resulting from homologous recombination with the disruption plasmid, were identified but were shown to be accompanied by deletions of the surrounding genomic region.
Nelson
J A
JA
Department of Genetics and Cell Biology, University of Minnesota, St. Paul 55108, USA.
Lefebvre
P A
PA
D000818:Animals; D002352:Carrier Proteins / Q000235:genetics*; D016825:Chlamydomonas reinhardtii / Q000235:genetics* / Q000254:growth & development; D002704:Chlorates / Q000494:pharmacology; D004640:Emetine / Q000494:pharmacology; D018390:Gene Targeting / Q000379:methods*; D017125:Genes, Protozoan / Q000235:genetics; D005819:Genetic Markers; D005822:Genetic Vectors / Q000235:genetics; D047908:Intracellular Signaling Peptides and Proteins; D005810:Multigene Family / Q000235:genetics; D016296:Mutagenesis; D009566:Nitrates; D009687:Nuclear Proteins / Q000235:genetics*; D015800:Protozoan Proteins; D012269:Ribosomal Proteins / Q000235:genetics; D014170:Transformation, Genetic
D002352:Carrier Proteins; D002704:Chlorates; D005819:Genetic Markers; D047908:Intracellular Signaling Peptides and Proteins; C095726:NIT8 protein, Chlamydomonas reinhardtii; D009566:Nitrates; D009687:Nuclear Proteins; D015800:Protozoan Proteins; D012269:Ribosomal Proteins; C039747:ribosomal protein S14; D004640:Emetine; C022842:chloric acid