Positive selection for sensitivity of Chlamydomonas reinhardtii to photosystem II-inhibiting herbicides
1989
Galloway, R. | Mets, L.
We have developed a method for the strong positive selection of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU or diuron) -sensitive mutants of the unicellular green alga Chlamydomonas reinhardtii. The method involves plating cells in the light on medium containing acetate with carefully balanced concentrations of diuron and metronidazole. We have used this method for the selection of sensitive revertants of diuron-resistant strain Dr2. Among the strains that survive the selection, the spectrum of mutant phenotypes is diverse. These include reduced or absent photosynthesis, altered pigment content or chlorophyll fluorescence induction kinetics, as well as increased herbicide sensitivity. Among the more sensitive strains characterized in detail were five with increased affinity of diuron binding to the thylakoid membranes. None of these mutants is as sensitive as wild type, and so none is an exact revertant of mutant Dr2. All of these mutants showed the non-mendelian inheritance pattern characteristic of chloroplast DNA. Thus, the results extend the previous conclusion that the Photosystem II herbicide binding site is under the exclusive control of the chloroplast genome.
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