title: Genetic identification of a second site modifier of ctr1-1 that controls ethylene-responsive and gravitropic root growth in Arabidopsis thaliana.
abstract: Ethylene controls myriad aspects of plant growth throughout developmental stages in higher plants. It has been well established that ethylene-responsive growth entails extensive crosstalk with other plant hormones, particularly auxin. Here, we report a genetic mutation, named 1-aminocyclopropane carboxylic acid (ACC) resistant root1-1 (are1-1) in Arabidopsis thaliana (L.) Heynh. The CONSTITUTIVE TRIPLE RESPONSE1 (CTR1) encodes a Raf-related protein, functioning as an upstream negative regulator of ethylene signaling in Arabidopsis thaliana. We found that the ctr1-1, a kinase-inactive allele exhibited slightly, but significantly, longer root length, compared to ACC-treated wild-type or ctr1-3, a null allele. Our genetic studies unveiled the existence of are1-1 mutation in the ctr1-1 mutant, as a second-site modifier which confers root-specific ethylene-resistance. Based on well-characterized crosstalk between ethylene and auxin during ethylene-responsive root growth, we performed various physiological analyses. Whereas are1-1 displayed normal sensitivity to synthetic auxins, it showed modest resistance to an auxin transport inhibitor, 1-Nnaphthylphthalamic acid. In addition, are1-1 mutant exhibited ectopically altered DR5:GUS activity upon ethylenetreatment. The results implicated the involvement of are1-1 in auxin-distribution, but not in auxin-biosynthesis, -uptake, or -sensitivity. In agreement, are1-1 mutant exhibited reduced gravitropic root growth and defective redistribution of DR5:GUS activity upon gravi-stimulation. Taken together with genetic and molecular analysis, our results suggest that ARE1 defines a novel locus to control ethylene-responsive root growth as well as gravitropic root growth presumably through auxin distribution in Arabidopsis thaliana.
authors.affiliation: Department of Molecular Biology, College of Life Science, Sejong University, Seoul, 143-747, Korea.
authors.forename: Kihye
authors.initials: K
authors.lastname: Shin
authors.forename: Rin-A
authors.initials: RA
authors.lastname: Lee
authors.forename: Inhye
authors.initials: I
authors.lastname: Lee
authors.forename: Sumin
authors.initials: S
authors.lastname: Lee
authors.forename: Soon Ki
authors.initials: SK
authors.lastname: Park
authors.forename: Moon-Soo
authors.initials: MS
authors.lastname: Soh
mesh_terms: D000483:Alleles; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development*; D002874:Chromosome Mapping; D032461:Chromosomes, Plant / Q000235:genetics; D005030:Ethylenes / Q000494:pharmacology*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D016153:Genes, Suppressor; D005816:Genetic Complementation Test; D018522:Gravitropism / Q000187:drug effects* / Q000235:genetics; D007210:Indoleacetic Acids / Q000494:pharmacology; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D018517:Plant Roots / Q000187:drug effects / Q000235:genetics / Q000254:growth & development*; D030821:Plants, Genetically Modified; D011494:Protein Kinases / Q000235:genetics* / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects / Q000254:growth & development
chemical_list: D005030:Ethylenes; D007210:Indoleacetic Acids; C036216:ethylene; D011494:Protein Kinases; C477753:CTR1 protein, Arabidopsis