title: An early ethylene up-regulated gene encoding a calmodulin-binding protein involved in plant senescence and death.
abstract: 35S-Labeled calmodulin (CaM) was used to screen a tobacco anther cDNA library. A positive clone (NtER1) with high homology to an early ethylene-up-regulated gene (ER66) in tomato, and an Arabidopsis homolog was isolated and characterized. Based on the helical wheel projection, a 25-mer peptide corresponding to the predicted CaM-binding region of NtER1 (amino acids 796-820) was synthesized. The gel-mobility shift assay showed that the peptide formed a stable complex with CaM only in the presence of Ca(2+). CaM binds to NtER1 with high affinity (K(d) approximately 12 nm) in a calcium-dependent manner. Tobacco flowers at different stages of development were treated with ethylene or with 1-methylcyclopropene for 2 h before treating with ethylene. Northern analysis showed that the NtER1 was rapidly induced after 15 min of exposure to ethylene. However, the 2-h 1-methylcyclopropene treatment totally blocked NtER1 expression in flowers at all stages of development, suggesting that NtER1 is an early ethylene-up-regulated gene. The senescing leaves and petals had significantly increased NtER1 induction as compared with young leaves and petals, implying that NtER1 is developmentally regulated and acts as a trigger for senescence and death. This is the first documented evidence for the involvement of Ca(2+)/CaM-mediated signaling in ethylene action.
authors.affiliation: Laboratory of Plant Molecular Biology and Physiology, Department of Horticulture, Washington State University, Pullman, Washington 99164-6414, USA.
authors.forename: T
authors.initials: T
authors.lastname: Yang
authors.forename: B W
authors.initials: BW
authors.lastname: Poovaiah
mesh_terms: D000595:Amino Acid Sequence; D017360:Arabidopsis / Q000235:genetics; D001483:Base Sequence; D002147:Calmodulin / Q000378:metabolism; D002148:Calmodulin-Binding Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D003001:Cloning, Molecular; D005030:Ethylenes / Q000494:pharmacology*; D018506:Gene Expression Regulation, Plant / Q000187:drug effects*; D015723:Gene Library; D007700:Kinetics; D018551:Solanum lycopersicum / Q000235:genetics; D008969:Molecular Sequence Data; D010446:Peptide Fragments / Q000737:chemistry; D010940:Plant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D010947:Plants, Toxic; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014026:Nicotiana / Q000235:genetics / Q000254:growth & development / Q000502:physiology*
chemical_list: D002147:Calmodulin; D002148:Calmodulin-Binding Proteins; C418110:ER1, Nicotiana tabacum; D005030:Ethylenes; D010446:Peptide Fragments; D010940:Plant Proteins; C036216:ethylene