title: Calcium-regulated in vivo protein phosphorylation in Zea mays L. root tips.
abstract: Calcium dependent protein phosphorylation was studied in corn (Zea mays L.) root tips.  Prior to in vivo protein phosphorylation experiments, the effect of calcium, ethyleneglycol-bis-(beta-aminoethyl ether)-N-N'  -tetraacetic acid (EGTA) and calcium ionophore (A-23187) on phosphorus uptake was studied.  Calcium increased phosphorus uptake, whereas EGTA and A-23187 decreased it.  Consequently, phosphorus concentration in the media was adjusted so as to attain similar uptake in different treatments.  Phosphoproteins were analyzed by two-dimensional gel electrophoresis.  Distinct changes in phosphorylation were observed following altered calcium levels.  Calcium depletion in root tips with EGTA and A-23187 decreased protein phosphorylation.  However, replenishment of calcium following EGTA and ionophore pretreatment enhanced phosphorylation of proteins.  Preloading of the root tips with 32P in the presence of EGTA and A-23187 followed by a ten minute calcium treatment, resulted in increased phosphorylation indicating the involvement of calcium, calcium and calmodulin-dependent kinases.  Calmodulin antagonist W-7 was effective in inhibiting calcium-promoted phosphorylation.  These studies suggest a physiological role for calcium-dependent phosphorylation in calcium-mediated processes in plants.
authors.affiliation: Department of Horticulture and Landscape Architecture, Washington State University, Pullman 99164-6414, USA.
authors.forename: K G
authors.initials: KG
authors.lastname: Raghothama
authors.forename: A S
authors.initials: AS
authors.lastname: Reddy
authors.forename: M
authors.initials: M
authors.lastname: Friedmann
authors.forename: B W
authors.initials: BW
authors.lastname: Poovaiah
mesh_terms: D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*; D002147:Calmodulin / Q000037:antagonists & inhibitors; D002614:Chelating Agents / Q000494:pharmacology; D004533:Egtazic Acid / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D010758:Phosphorus / Q000493:pharmacokinetics*; D010766:Phosphorylation; D010940:Plant Proteins / Q000737:chemistry / Q000378:metabolism* / Q000502:physiology; D018517:Plant Roots / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D013449:Sulfonamides / Q000494:pharmacology; D003313:Zea mays / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology
chemical_list: D002147:Calmodulin; D002614:Chelating Agents; D007476:Ionophores; D010940:Plant Proteins; D013449:Sulfonamides; D010758:Phosphorus; D000001:Calcimycin; D004533:Egtazic Acid; C017967:W 7; D002118:Calcium