title: A mutation in the alpha 1-tubulin gene of Chlamydomonas reinhardtii confers resistance to anti-microtubule herbicides.
abstract: A mutation in the alpha 1-tubulin gene of Chlamydomonas reinhardtii was isolated by using the amiprophos-methyl-resistant mutation apm1-18 as a background to select new mutants that showed increased resistance to the drug. The upA12 mutation caused twofold resistance to amiprophos-methyl and oryzalin, and twofold hypersensitivity to the microtubule-stabilizing drug taxol, suggesting that the mutation enhanced microtubule stability. The resistance mutation was semi-dominant and mapped to the same interval on linkage group III as the alpha 1-tubulin gene. Two-dimensional gel immunoblots of proteins in the mutant cells revealed two electrophoretically altered alpha-tubulin isoforms, one of which was acetylated and incorporated into microtubules in the axoneme. The mutant isoforms co-segregated with the drug-resistance phenotypes when mutant upA12 was backcrossed to wild-type cells. Two-dimensional gel analysis of in vitro translation products showed that the non-acetylated variant alpha-tubulin was a primary gene product. DNA sequence analysis of the alpha 1-tubulin genes from mutant and wild-type cells revealed a single missense mutation, which predicted a change in codon 24 from tyrosine in wild type to histidine in mutant upA12. This alteration in the predicted amino acid sequence corroborated the approximately +1 basic charge shift observed for the variant alpha-tubulins. The mutant allele of the alpha 1-tubulin gene was designated tua1-1.
authors.affiliation: Department of Genetics and Cell Biology, University of Minnesota, St. Paul 55108-1095.
authors.forename: S W
authors.initials: SW
authors.lastname: James
authors.forename: C D
authors.initials: CD
authors.lastname: Silflow
authors.forename: P
authors.initials: P
authors.lastname: Stroom
authors.forename: P A
authors.initials: PA
authors.lastname: Lefebvre
mesh_terms: D000107:Acetylation; D000483:Alleles; D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000187:drug effects / Q000235:genetics*; D004252:DNA Mutational Analysis; D004136:Dinitrobenzenes / Q000494:pharmacology*; D004351:Drug Resistance; D017343:Genes, Plant; D017125:Genes, Protozoan; D008870:Microtubules / Q000187:drug effects*; D009578:Nitrobenzenes; D009946:Organothiophosphorus Compounds / Q000494:pharmacology*; D017239:Paclitaxel / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics*; D011499:Protein Processing, Post-Translational; D015800:Protozoan Proteins / Q000235:genetics*; D013424:Sulfanilamides; D014404:Tubulin / Q000235:genetics*
chemical_list: D004136:Dinitrobenzenes; D009578:Nitrobenzenes; D009946:Organothiophosphorus Compounds; D010940:Plant Proteins; D015800:Protozoan Proteins; D013424:Sulfanilamides; D014404:Tubulin; C011402:amiprophos; C012465:oryzalin; D017239:Paclitaxel