title: The axr2-1 mutation of Arabidopsis thaliana is a gain-of-function mutation that disrupts an early step in auxin response.
abstract: The dominant axr2-1 mutation of Arabidopsis thaliana confers resistance to the plant hormones auxin, ethylene, and abscisic acid. In addition, axr2-1 has pleiotropic effects on plant morphology which include gravitropic defects in roots, hypocotyls and inflorescences of axr2-1 plants. Two genetic screens were conducted to isolate new mutations at the AXR2 locus. First, axr2-1 pollen was gamma-irradiated, crossed onto wild-type plants, and the M1 progeny screened for loss of the axr2-1 phenotype. Large deletions of the axr2-1 region on chromosome 3 resulted; however, none of these deletions appeared to be heritable. In the second, M2 seed obtained from axr2-1 gl-1 plants was screened for reversion of the axr2-1 phenotype. One revertant line, axr2-r3, has a distinctive phenotype caused by a second mutation at the axr2 locus. To learn more about the nature of the axr2-1 mutation, the effects of varying the ratio of wild-type to mutant copies of the AXR2 gene were examined by comparing plants of the following genotypes: +/+, +/+/+, axr2-1/axr2-1, axr2-1/+ and axr2-1/+/+. Additionally, accumulation of transcripts from the auxin-inducible SAUR-AC1 gene was examined to determine the response of wild-type and mutant plants to auxin. Wild-type seedlings and mature plants accumulate transcripts with auxin treatment. In contrast, axr2-1 tissue does not accumulate SAUR-AC1 transcripts in response to auxin. Taken together, these results indicate that axr2-1 is a neomorphic or hypermorphic mutation that disrupts an early step in an auxin response pathway.
authors.affiliation: Department of Biology, Indiana University, Bloomington 47405.
authors.forename: C
authors.initials: C
authors.lastname: Timpte
authors.forename: A K
authors.initials: AK
authors.lastname: Wilson
authors.forename: M
authors.initials: M
authors.lastname: Estelle
mesh_terms: D017360:Arabidopsis / Q000235:genetics* / Q000254:growth & development; D029681:Arabidopsis Proteins; D002874:Chromosome Mapping; D005720:Gamma Rays; D017353:Gene Deletion; D018628:Gene Dosage; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005799:Genes, Dominant; D017343:Genes, Plant / Q000528:radiation effects; D005808:Genes, Recessive; D007210:Indoleacetic Acids / Q000502:physiology*; D009154:Mutation; D010641:Phenotype; D010940:Plant Proteins / Q000235:genetics; D011058:Pollen / Q000528:radiation effects
chemical_list: D029681:Arabidopsis Proteins; D007210:Indoleacetic Acids; D010940:Plant Proteins; C086789:SAUR-AC1 protein, Arabidopsis