title: A stress-responsive caleosin-like protein, AtCLO4, acts as a negative regulator of ABA responses in Arabidopsis.
abstract: Caleosins or related sequences have been found in a wide range of higher plants. In Arabidopsis, seed-specific caleosins are viewed as oil-body (OB)-associated proteins that possess Ca(2+)-dependent peroxygenase activity and are involved in processes of lipid degradation. Recent experimental evidence suggests that one of the Arabidopsis non-seed caleosins, AtCLO3, is involved in controlling stomatal aperture during the drought response; the roles of the other caleosin-like proteins in Arabidopsis remain largely uncharacterized. We have demonstrated that a novel stress-responsive and OB-associated Ca(2+)-binding caleosin-like protein, AtCLO4, is expressed in non-seed tissues of Arabidopsis, including guard cells, and down-regulated following exposure to exogenous ABA and salt stress. At the seed germination stage, a loss-of-function mutant (atclo4) was hypersensitive to ABA, salt and mannitol stresses, whereas AtCLO4-overexpressing (Ox) lines were more hyposensitive to those stresses than the wild type. In adult stage, atclo4 mutant and AtCLO4-Ox plants showed enhanced and decreased drought tolerance, respectively. Following exposure to exogenous ABA, the expression of key ABA-dependent regulatory genes, such as ABF3 and ABF4, was up-regulated in the atclo4 mutant, while it was down-regulated in AtCLO4-Ox lines. Based on these results, we propose that the OB-associated Ca(2+)-binding AtCLO4 protein acts as a negative regulator of ABA responses in Arabidopsis.
authors.affiliation: School of Life Sciences and Biotechnology, Korea University, Seoul 136-701, Korea.
authors.forename: Yun Young
authors.initials: YY
authors.lastname: Kim
authors.forename: Kwang Wook
authors.initials: KW
authors.lastname: Jung
authors.forename: Kyoung Shin
authors.initials: KS
authors.lastname: Yoo
authors.forename: Ji Ung
authors.initials: JU
authors.lastname: Jeung
authors.forename: Jeong Sheop
authors.initials: JS
authors.lastname: Shin
mesh_terms: D000040:Abscisic Acid / Q000494:pharmacology*; D000222:Adaptation, Physiological / Q000187:drug effects; D017360:Arabidopsis / Q000166:cytology / Q000187:drug effects* / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D004269:DNA, Bacterial / Q000235:genetics; D055864:Droughts; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D055785:Gene Knockdown Techniques; D017343:Genes, Plant / Q000235:genetics; D018525:Germination / Q000187:drug effects; D008353:Mannitol / Q000494:pharmacology; D016254:Mutagenesis, Insertional / Q000187:drug effects / Q000235:genetics; D009154:Mutation / Q000235:genetics; D009928:Organ Specificity / Q000187:drug effects; D010940:Plant Proteins / Q000378:metabolism*; D054046:Plant Stomata / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D058526:Plant Vascular Bundle / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D030821:Plants, Genetically Modified; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000187:drug effects; D012639:Seeds / Q000187:drug effects / Q000254:growth & development; D015398:Signal Transduction / Q000235:genetics; D012965:Sodium Chloride / Q000494:pharmacology; D013312:Stress, Physiological / Q000187:drug effects*; D013347:Subcellular Fractions / Q000187:drug effects / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D002135:Calcium-Binding Proteins; D004269:DNA, Bacterial; D010940:Plant Proteins; C036483:T-DNA; C402836:caleosin protein, Sesamum indicum; D008353:Mannitol; D012965:Sodium Chloride; D000040:Abscisic Acid