ABSTRACT
The FT37/1 tumor line induced by Agrobacterium tumefaciens on flax epicotyls contains 22-24 copies of the T-DNA encoded nopaline synthase gene per cell. All the gene copies are methylated to some extent but the methylation is not uniform, nor does it reflect the methylation level of the flanking plant DNA. This extensive methylation correlates with an extremely low level of expression of the nopaline synthase gene. Treatment of the tumor line with the in vivo demethylating drug 5-azacytidine at a concentration of 3 X 10(-5) M, resulted in the demethylation of, on average, one copy of the nopaline synthase gene per cell. This demethylation was paralleled by an increase in the transcription of the gene and indicates that cytosine methylation is capable of suppressing the expression of plant genes in vivo.
Subject(s)
Amino Acid Oxidoreductases/genetics , Cytosine/metabolism , Gene Expression Regulation , Plant Tumors/enzymology , Amino Acid Oxidoreductases/metabolism , Azacitidine/pharmacology , DNA/genetics , DNA/metabolism , DNA, Neoplasm/genetics , DNA, Neoplasm/metabolism , Malate Dehydrogenase/metabolism , Methylation , Rhizobium/pathogenicityABSTRACT
The stereospecificity of octopine dehydrogenase from crown gall tumor and of octopine dehydrogenase from scallops (Pecten maximum) with respect to the oxidation of C-4 of the dihydronicotinamide ring of NADH was investigated by determination of the distribution of radioactivity after oxidation of (4R)- and (4S)-[4-3H]NADH. Octopine dehydrogenase from crown gall tumor and from scallops stereospecifically removes the pro-S hydrogen atom of the dihydronicotinamide ring with transfer of label to the solvent and to the product octopine (N-2-(1-carboxyethyl)-L-arginine). Although to a lesser extent, the exchange of label from (4S)-[4-3H]NADH with solvent was found to occur when octopine dehydrogenase from either crown gall tumor or from scallops was incubated in the absence of other substrates. Possible mechanisms to explain this exchange are discussed.
Subject(s)
Amino Acid Oxidoreductases/metabolism , Mollusca/enzymology , NAD/metabolism , Plant Tumors/enzymology , Animals , Models, Chemical , Oxidation-ReductionABSTRACT
A rapid and sensitive method has been developed to determine lysopine dehydrogenase (EC 1.5.1-) and nopaline dehydrogenase activities in crown gall tumour tissues. By this method, enzyme activities as low as 0.2 micrometerol octopine or nopaline per h per g fresh weight tumour tissue can still be detected. In non-infected young pea seedlings, no lysopine dehydrogenase activity was detected.
Subject(s)
D-Amino-Acid Oxidase/analysis , Oxidoreductases Acting on CH-NH Group Donors/analysis , Plant Tumors/enzymology , Rhizobium , Arginine/analogs & derivatives , Glutarates , Lysine/analogs & derivatives , Microchemistry/methodsABSTRACT
Axenic cultures of normal, habituated and crown gall teratoma were grown under varying conditions to examine the effects of environment on the expression of neoplastic character. Acid phosphatase patterns on polyacrylamide gels did not vary greatly among tissues although there were differences in acid phosphatase activity between various strains of Agrobacterium tumefaciens, the bacteria which cause crown gall. Certain esterase isoenzymes were found only in tissues grown on specific media, while others were tissue-specific but independent of the nature of the medium. Comparisons of liquid and solid grown cultures revealed that culture conditions also influence esterase expression. Both sunflower and tobacco crown gall tissue contained an esterase not found in habituated or normal tissues, and similar in electrophoretic mobility to an esterase found in extracts of the bacteria that had induced the tumors. The basic difference between the three tissue types studied is the manner in which they respond to a given environment.
Subject(s)
Acid Phosphatase/metabolism , Esterases/metabolism , Isoenzymes/metabolism , Nicotiana/enzymology , Plant Tumors/enzymology , Plants, Toxic , Cell Transformation, Neoplastic , Culture Techniques , Plant Tumors/etiology , Rhizobium/enzymologySubject(s)
Plant Tumors/enzymology , Plant Viruses , RNA Nucleotidyltransferases/metabolism , RNA-Dependent RNA Polymerase/metabolism , Ammonium Chloride/pharmacology , Hydrogen-Ion Concentration , Magnesium/pharmacology , Plants/drug effects , RNA, Viral/biosynthesis , Temperature , Virus ReplicationSubject(s)
Cell Transformation, Neoplastic , Flavins/physiology , Neoplasms/metabolism , 2,4-Dichlorophenoxyacetic Acid/pharmacology , Animals , Carcinogens/pharmacology , Cell Transformation, Neoplastic/metabolism , Coenzymes/metabolism , Darkness , Dose-Response Relationship, Drug , Drug Interactions , Energy Metabolism , Flavins/metabolism , Humans , Indoleacetic Acids/physiology , Light , Liver/metabolism , Mice , Neoplasms/enzymology , Neoplasms/etiology , Neoplasms, Experimental/metabolism , Plant Tumors/enzymology , Plant Tumors/metabolism , Rats , Riboflavin/metabolism , Riboflavin Deficiency/metabolism , Succinate Dehydrogenase/metabolismABSTRACT
One member of a new class of cell-division-promoting factors, that has been given the trivial name of cytokinesin I, is a potent inhibitor of adenosine 3':5'-cyclic monophosphate phosphodiesterases of both plant and animal origin. Since an adenylate cyclase has been demonstrated in this study to be present in plant cells, the results suggest that cytokinesin I may be exerting its biological effects in promoting division in cells of higher plant species as a regulator of adenosine 3':5'-cyclic monophosphate.
