title: Genetic interactions among Chlamydomonas reinhardtii mutations that confer resistance to anti-microtubule herbicides.
abstract: We previously described two types of genetic interactions among recessive mutations in the APM1 and APM2 loci of Chlamydomonas reinhardtii that may reflect a physical association of the gene products or their involvement in a common structure/process: (1) allele-specific synthetic lethality, and (2) unlinked noncomplementation, or dominant enhancement. To further investigate these interactions, we isolated revertants in which the heat sensitivity caused by the apm2-1 mutation is lost. The heat-insensitive revertants were either fully or partially suppressed for the drug-resistance caused by the apm2-1 allele. In recombination tests the revertants behaved as if the suppressing mutation mapped within the APM2 locus; the partial suppressors of apm2-1 herbicide resistance failed to complement apm2-1, leading to the conclusion that they were likely to be intragenic pseudorevertants. The apm2-1 partial suppressor mutations reversed apm1-apm2-1 synthetic lethality in an allele-specific manner with respect both to apm1- alleles and apm2-1 suppressor mutations. Those apm1- apm2-1rev strains that regained viability also regained heat sensitivity characteristic of the original apm2-1 mutation, even though the apm2-1 suppressor strains were fully heat-insensitive. The Hs+ phenotypes of apm2-1 partial suppressors were also reversed by treatment with the microtubule-stabilizing agent deuterium oxide (D2O). In addition to the above interactions, we observed interallelic complementation and phenotypic enhancement of temperature conditionality among apm1- alleles. Evidence of a role for the products of the two genes in microtubule-based processes was obtained from studying flagellar assembly in apm1- and apm2- mutants.
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: P A
authors.initials: PA
authors.lastname: Lefebvre
mesh_terms: D000483:Alleles; D000818:Animals; D016825:Chlamydomonas reinhardtii / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D003903:Deuterium / Q000494:pharmacology; D017666:Deuterium Oxide; D004351:Drug Resistance / Q000235:genetics; D005407:Flagella / Q000187:drug effects / Q000502:physiology; D006540:Herbicides / Q000494:pharmacology; D006358:Hot Temperature; D008870:Microtubules / Q000187:drug effects; D009154:Mutation; D009578:Nitrobenzenes; D009946:Organothiophosphorus Compounds / Q000494:pharmacology; D010641:Phenotype; D012038:Regeneration / Q000187:drug effects; D014867:Water / Q000494:pharmacology
chemical_list: D006540:Herbicides; D009578:Nitrobenzenes; D009946:Organothiophosphorus Compounds; D014867:Water; C017823:amiprophos methyl; D003903:Deuterium; D017666:Deuterium Oxide