title: The bZIP Protein VIP1 Is Involved in Touch Responses in Arabidopsis Roots.
abstract: VIP1 is a bZIP transcription factor in Arabidopsis (Arabidopsis thaliana). VIP1 transiently accumulates in the nucleus when cells are exposed to hypoosmotic conditions, but its physiological relevance is unclear. This is possibly because Arabidopsis has approximately 10 close homologs of VIP1 and they function redundantly. To examine their physiological roles, transgenic plants overexpressing a repression domain-fused form of VIP1 (VIP1-SRDXox plants), in which the gene activation mediated by VIP1 is expected to be repressed, were generated. Because hypoosmotic stress can mimic mechanical stimuli (e.g. touch), the touch-induced root-waving phenotypes and gene expression patterns in those transgenic plants were examined. VIP1-SRDXox plants exhibited more severe root waving and lower expression of putative VIP1 target genes. The expression of the VIP1-green fluorescent protein (GFP) fusion protein partially suppressed the VIP1-SRDX-induced increase in root waving when expressed in the VIP1-SRDXox plants. These results suggest that VIP1 can suppress the touch-induced root waving. The VIP1-SRDX-induced increase in root waving was also suppressed when the synthetic auxin 2,4-dichlorophenoxy acetic acid or the ethylene precursor 1-aminocyclopropane-1-carboxylic acid, which is known to activate auxin biosynthesis, was present in the growth medium. Root cap cells with the auxin marker DR5rev::GFP were more abundant in the VIP1-SRDXox background than in the wild-type background. Auxin is transported via the root cap, and the conditions of outermost root cap layers were abnormal in VIP1-SRDXox plants. These results raise the possibility that VIP1 influences structures of the root cap and thereby regulates the local auxin responses in roots.
authors.affiliation: Laboratory of Crop Physiology, Research Faculty of Agriculture, Hokkaido University, Sapporo-shi, Hokkaido 060-8589, Japan (D.T.);Asian Natural Environmental Science Center, University of Tokyo, Nishitokyo-shi, Tokyo 188-0002, Japan (D.T., T.T.); andAlkali Soil Natural Environmental Science Center, Northeast Forestry University, Xiangfang District, Harbin 150040, People's Republic of China (S.L.) tsugama@res.agr.hokudai.ac.jp.
authors.forename: Daisuke
authors.identifier: 0000-0002-4946-678X
authors.initials: D
authors.lastname: Tsugama
authors.affiliation: Laboratory of Crop Physiology, Research Faculty of Agriculture, Hokkaido University, Sapporo-shi, Hokkaido 060-8589, Japan (D.T.);Asian Natural Environmental Science Center, University of Tokyo, Nishitokyo-shi, Tokyo 188-0002, Japan (D.T., T.T.); andAlkali Soil Natural Environmental Science Center, Northeast Forestry University, Xiangfang District, Harbin 150040, People's Republic of China (S.L.).
authors.forename: Shenkui
authors.initials: S
authors.lastname: Liu
authors.affiliation: Laboratory of Crop Physiology, Research Faculty of Agriculture, Hokkaido University, Sapporo-shi, Hokkaido 060-8589, Japan (D.T.);Asian Natural Environmental Science Center, University of Tokyo, Nishitokyo-shi, Tokyo 188-0002, Japan (D.T., T.T.); andAlkali Soil Natural Environmental Science Center, Northeast Forestry University, Xiangfang District, Harbin 150040, People's Republic of China (S.L.).
authors.forename: Tetsuo
authors.initials: T
authors.lastname: Takano
mesh_terms: D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000378:metabolism*; D050976:Basic-Leucine Zipper Transcription Factors / Q000378:metabolism*; D018744:DNA, Plant / Q000378:metabolism; D005030:Ethylenes / Q000096:biosynthesis; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D005838:Genotype; D049452:Green Fluorescent Proteins / Q000378:metabolism; D007210:Indoleacetic Acids / Q000494:pharmacology; D009995:Osmosis; D018517:Plant Roots / Q000166:cytology / Q000187:drug effects / Q000254:growth & development / Q000502:physiology*; D030821:Plants, Genetically Modified; D011485:Protein Binding / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D013312:Stress, Physiological / Q000187:drug effects / Q000235:genetics; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism; D014110:Touch
chemical_list: D029681:Arabidopsis Proteins; D050976:Basic-Leucine Zipper Transcription Factors; D018744:DNA, Plant; D005030:Ethylenes; D007210:Indoleacetic Acids; C432104:VIP1 protein, Arabidopsis; D049452:Green Fluorescent Proteins; C036216:ethylene