calcimycin and gibberellic-acid

Hemoglobin gene expression is upregulated during hypoxia. To determine whether the induction occurs via similar mechanisms that have been proposed for other hypoxically induced proteins, barley (Hordeum vulgare L.) aleurone layers were treated with various agents that interfere with known components of signal transduction. Ruthenium red, an organelle calcium channel blocker, inhibited anoxia-induced hemoglobin (Hb) and alcohol dehydrogenase (EC 1.1.1.1) (Adh) gene expression in a dose-dependent manner. The divalent ionophore, A23187, combined with EGTA also dramatically reduced anoxia-induced Hb and Adh expression. Normal induction of Hb by anoxia in EGTA-treated cells was restored by adding exogenous Ca2+ but not Mg2+, suggesting that cytosolic calcium is involved in Hb and Adh regulation. W-7, a calmodulin antagonist, did not affect anaerobically induced Hb and Adh expression even though it induced Hb under aerobiosis. A3, a protein kinase inhibitor, did not significantly affect anaerobically induced Hb, but did significantly upregulate the gene under aerobic conditions. The results indicate that calmodulin-independent anaerobic alteration in cytosolic Ca2+ and protein dephosphorylation are factors in Hb induction.

Topics: alpha-Amylases; Calcimycin; Calcium; Calcium-Calmodulin-Dependent Protein Kinases; Cytosol; Egtazic Acid; Gene Expression Regulation, Plant; Gibberellins; Hemoglobins; Hordeum; Nuclear Proteins; Phosphorylation; Plant Proteins; Protein Kinase Inhibitors; Ruthenium Red; Signal Transduction; Sulfonamides; Up-Regulation

Fructose-bisphosphate aldolase is a glycolytic enzyme whose activity increases in rice roots treated with gibberellin (GA). To investigate the relationship between aldolase and root growth, GA-induced root aldolase was characterized. GA3 promoted an increase in aldolase accumulation when 0.1 microM GA3 was added exogenously to rice roots. Aldolase accumulated abundantly in roots, especially in the apical region. To examine the effect of aldolase function on root growth, transgenic rice plants expressing antisense aldolase were constructed. Root growth of aldolase-antisense transgenic rice was repressed compared with that of the vector control transgenic rice. Although aldolase activity increased by 25% in vector control rice roots treated with 0.1 microM GA3, FBPA activity increased very little by 0.1 microM GA3 treatment in the root of aldolase-antisense transgenic rice. Furthermore, aldolase co-immunoprecipitated with antibodies against vacuolar H+ -ATPase in rice roots. In the root of OsCDPK13-antisense transgenic rice, aldolase did not accumulate even after treatment with GA3. These results suggest that the activation of glycolytic pathway function accelerates root growth and that GA3-induced root aldolase may be modulated through OsCDPK13. Aldolase physically associates with vacuolar H-ATPase in roots and may regulate the vacuolar H-ATPase mediated control of cell elongation that determines root length.

Topics: Blotting, Western; Calcimycin; Calcium; DNA, Antisense; Dose-Response Relationship, Drug; Fructose-Bisphosphate Aldolase; Gene Expression Regulation, Enzymologic; Gene Expression Regulation, Plant; Gibberellins; Immunoprecipitation; Ionophores; Lanthanum; Oryza; Plant Growth Regulators; Plant Proteins; Plant Roots; Plants, Genetically Modified; Protein Kinases; RNA, Messenger; Seedlings; Vacuolar Proton-Translocating ATPases