title: Hypoxia-inducible genes encoding small EF-hand proteins in rice and tomato.
abstract: Rice has evolved metabolic and morphological adaptations to low-oxygen stress to grow in submerged paddy fields. To characterize the molecular components that mediate the response to hypoxia in rice, we identified low-oxygen stress early response genes by microarray analysis. Among the highly responsive genes, five genes, OsHREF1 to OsHREF5, shared strong homology. They encoded small proteins harboring two EF-hands, typical Ca(2+)-binding motifs. Homologous genes were found in many land plants, including SlHREF in tomato, which is also strongly induced by hypoxia. SlHREF induction was detected in both roots and shoots of tomato plants under hypoxia. With the exception of OsHREF5, OsHREF expression was unaffected by drought, salinity, cold, or osmotic stress. Fluorescent signals of green fluorescent protein-fused OsHREFs were detected in the cytosol and nucleus. Ruthenium red, an inhibitor of intracellular Ca(2+) release, repressed induction of OsHREF1-4 under hypoxia. The HREFs may be related to the Ca(2+) response to hypoxia.
authors.affiliation: Research Institute for Biological Sciences, Okayama Prefectural Technology Center for Agriculture, Forestry, and Fisheries, Okayama, Japan.
authors.forename: Chie
authors.initials: C
authors.lastname: Otsuka
authors.forename: Ikuko
authors.initials: I
authors.lastname: Minami
authors.forename: Kenji
authors.initials: K
authors.lastname: Oda
mesh_terms: D000595:Amino Acid Sequence; D003080:Cold Temperature; D003513:Cycloheximide / Q000494:pharmacology; D055864:Droughts; D020832:EF Hand Motifs; D000860:Hypoxia / Q000235:genetics*; D042541:Intracellular Space / Q000378:metabolism; D018551:Solanum lycopersicum / Q000166:cytology / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D012275:Oryza / Q000166:cytology / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism; D009997:Osmotic Pressure; D010100:Oxygen / Q000378:metabolism; D010940:Plant Proteins / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D012091:Repetitive Sequences, Nucleic Acid; D012430:Ruthenium Red / Q000494:pharmacology; D012689:Sequence Homology, Nucleic Acid; D013997:Time Factors; D015533:Transcriptional Activation / Q000187:drug effects; D015854:Up-Regulation
chemical_list: D010940:Plant Proteins; D012430:Ruthenium Red; D003513:Cycloheximide; D010100:Oxygen