title: A chimeric Lhcb::Nia gene: an inducible counter selection system for mutants in the phytochrome signal transduction pathway.
abstract: One approach towards understanding the transduction pathways of phytochromes is the selection of mutants impaired in various steps. We report here the construction of an inducible counter-selection system for such mutants employing the enzyme nitrate reductase. This enzyme can convert the benign substrate analogue chlorate to the toxic product chlorite, resulting in severe growth inhibition. An Arabidopsis thaliana nitrate reductase gene (Nial*2) was placed under the regulation of an Arabidopsis thaliana light-harvesting chlorophyll a/b protein (Lhcb1*3) promoter that is phytochrome-responsive. The chimeric Lhcb::Nia gene was transformed into A. thaliana. Homozygous transformant lines were selected and grown in the absence of nitrate and the presence of L-glutamine, conditions that substantially inhibited the expression of the endogenous nitrate reductase genes. In darkness seedlings of the transformed lines were resistant to chlorate; however, when seedlings were grown with intermittent red light, increased sensitivity to chlorate was observed. This sensitivity was correlated with an increase in both Nia1*2 RNA levels and nitrate reductase activity. The resistant seedlings were clearly distinguishable from the sensitive ones based on hypocotyl length, with no overlap in this parameter between the two populations. Thus, this system should allow for the selection of mutants that are impaired in phytochrome regulation of the transcription of Lhcb genes.
authors.affiliation: Plant Adaptation Research Unit, J. Blaustein Institute for Desert Research, Ben-Gurion University of the Negev, Sede Boker, Israel.
authors.forename: Y M
authors.initials: YM
authors.lastname: Heimer
authors.forename: J A
authors.initials: JA
authors.lastname: Brusslan
authors.forename: D
authors.initials: D
authors.lastname: Kenigsbuch
authors.forename: E M
authors.initials: EM
authors.lastname: Tobin
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics*; D002704:Chlorates / Q000633:toxicity; D004274:DNA, Recombinant / Q000235:genetics; D004351:Drug Resistance; D018506:Gene Expression Regulation, Plant; D017343:Genes, Plant / Q000235:genetics; D045342:Light-Harvesting Protein Complexes; D009154:Mutation; D050901:Nitrate Reductase; D009565:Nitrate Reductases / Q000235:genetics; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics; D010834:Phytochrome / Q000378:metabolism*; D030821:Plants, Genetically Modified; D012641:Selection, Genetic; D015398:Signal Transduction / Q000235:genetics*; D014170:Transformation, Genetic
chemical_list: D002704:Chlorates; D004274:DNA, Recombinant; D045342:Light-Harvesting Protein Complexes; D045322:Photosynthetic Reaction Center Complex Proteins; D010834:Phytochrome; D009565:Nitrate Reductases; D050901:Nitrate Reductase