title: Isolation and characterization of novel mutants affecting the abscisic acid sensitivity of Arabidopsis germination and seedling growth.
abstract: To gain more insight into ABA signaling mechanisms, we conducted genetic screens searching for mutants with altered ABA response in germination and post-germination growth. We isolated seven putative ABA-hypersensitive Arabidopsis mutants and named them ABA-hypersensitive germination (ahg). These mutants exhibited diminished germination or growth ability on medium supplemented with ABA. We further studied four of them: ahg1, ahg2, ahg3 and ahg4. Mapping suggested that they were new ABA-hypersensitive loci. Characterization showed that all of them had enhanced sensitivity to salinity and high osmotic stress in germinating seeds, whereas they each had distinct sugar responses. RT-PCR experiments showed that the expression patterns of the ABA-inducible genes RAB18, AtEm1, AtEm6 and ABI5 in germinating seeds were affected by these four ahg mutations, whereas those of ABI3 and ABI4 were not. ahg4 displayed slightly increased mRNA levels of several ABA-inducible genes upon ABA treatment. By contrast, ahg1 had no clear ABA-hypersensitive phenotypes in adult plants despite its strong phenotype in germination. These results suggest that ahg1, ahg2, ahg3 and ahg4 are novel ABA-hypersensitive mutants representing distinct components in the ABA response.
authors.affiliation: Graduate School of Integrated Science, Yokohama City University, 1-7-29 Suehiro, Tsurumi, Yokohama, 230-0045 Japan.
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Nishimura
authors.forename: Tomo
authors.initials: T
authors.lastname: Yoshida
authors.forename: Maki
authors.initials: M
authors.lastname: Murayama
authors.forename: Tadao
authors.initials: T
authors.lastname: Asami
authors.forename: Kazuo
authors.initials: K
authors.lastname: Shinozaki
authors.forename: Takashi
authors.initials: T
authors.lastname: Hirayama
mesh_terms: D000040:Abscisic Acid / Q000378:metabolism* / Q000494:pharmacology; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D050976:Basic-Leucine Zipper Transcription Factors; D002874:Chromosome Mapping; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance / Q000235:genetics*; D018506:Gene Expression Regulation, Plant / Q000235:genetics; D005819:Genetic Markers; D018525:Germination / Q000235:genetics*; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D010937:Plant Growth Regulators / Q000378:metabolism / Q000494:pharmacology; D010940:Plant Proteins / Q000235:genetics / Q000378:metabolism; D036226:Seedlings / Q000187:drug effects / Q000235:genetics* / Q000254:growth & development*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D020691:rab GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: C409743:ABI5 protein, Arabidopsis; D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; D005819:Genetic Markers; D010937:Plant Growth Regulators; D010940:Plant Proteins; D014157:Transcription Factors; C066246:late embryogenesis abundant protein, plant; C078703:rab18 protein, Arabidopsis; D000040:Abscisic Acid; D020691:rab GTP-Binding Proteins