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J L Key

Publications and source records attributed to J L Key.

At least 91 records · Page 5Linked to original sources
PubMed1973

Influence of auxin and incubation on the relative level of polyribosomes in excised soybean hypocotyl.

The influence of incubation and auxin (2,4-D) on polyribosome level in soybean hypocotyl was studied.A marked drop in the relative level of polyribosomes in excised apical or meristematic tissue (0 to 5 millimeters below the cotyledons) occurred during incubation. The addition of auxin to the incubation medium did not affect polyribosome level. A similar decrease in polyribosome level occurred in excised elongating tissue (5 to 15 millimeters below cotyledons) during incubation. Auxin, however, caused a small but highly reproducible stabilization of polyribosomes in this tissue. There was a rapid, but small, auxin-independent increase in polyribosomes of basal or nongrowing hypocotyl (from 20 to 40 millimeters below cotyledons) during incubation, followed by a larger auxin-dependent increase in polyribosomes. While auxin is known to cause an increase in total ribosomes during incubation of the excised basal hypocotyl, the observed transformation from monoribosomes to polyribosomes was not dependent on new ribosome synthesis.Protein synthetic activity (poly U-directed phenylalanine incorporation) of the 80S monoribosomes at low Mg(2+) levels increased during incubation of the excised basal hypocotyl. The increase in ribosome activity was biphasic (an initial auxin-independent phase followed by an auxin-dependent increase in activity) correlating with the biphasic increase in polyribosomes. The enhanced activity of 80S monoribosomes was related, at least in part, to an increase in the level of peptidyl-tRNA associated with the ribosome population. Removal of peptidyl-tRNA from the ribosomes reversed the auxin effect.The hypothesis is advanced that the increase in polyribosomes in response to incubation and to auxin is preceded by and dependent upon the activation of 80S monoribosomes. This activation is in addition to a requirement for continued RNA synthesis, at least in part mRNA, for the transition from monoribosomes to polyribosomes.

Journal Article↗
PubMed1972

Characterization of Short Time Labeled Adenosine Monophosphate-rich Ribonucleic Acids of Soybean.

The total population of newly synthesized (32)P-AMP-rich RNA has been separated into two major types based on repeated fractionation on methylated albumin-kieselguhr columns. The purified D-RNA which elutes, under our experimental conditions, primarily in the salt gradient has a GMP/AMP ratio of about 0.8 and an AMP + UMP content of about 56 mole per cent. The purified TB-RNA which preferentially remains bound to the column in the salt gradient has a GMP/AMP ratio of about 0.4 to 0.45 and an AMP + UMP content of about 65 mole per cent. In addition to being distinguished by their fractionation on the methylated albumin-kieselguhr column and base composition analysis, purified D-RNA and TB-RNA have different size distributions on sucrose gradient and acrylamide gel fractionation, are differentially associated with polyribosomes and have different stabilities in the tissue.

Journal Article↗
PubMed1971

Inhibition of Auxin-induced Deoxyribonucleic Acid Synthesis and Chromatin Activity by 5-Fluorodeoxyuridine in Soybean Hypocotyl.

Rootless soybean (Glycine max) seedlings were used as a test system to examine the action of auxin on chromatin-directed RNA synthesis. Chromatin from the basal tissue of rootless seedlings (both control and auxin-treated) had RNA synthetic capacity similar to that of chromatin from comparably treated intact seedlings. When DNA synthesis normally induced in the basal tissue by auxin was blocked in the rootless seedlings by 5-fluorodeoxyuridine, the auxin enhancement of chromatin activity was inhibited 70%. This level was still three times the control level, indicating that auxin influenced the synthetic activity of existing DNA template. Experiments with Escherichia coli RNA polymerase revealed that chromatin from both auxin- and auxin plus 5-fluorodeoxyuridine-treated tissue saturated at higher levels than chromatin from control tissue.

Journal Article↗
PubMed1971

Dissociation of N(2) Gas-induced Monomeric Ribosomes and Functioning of the Derived Subunits in Protein Synthesis in Pea.

The dissociation of N(2) gas-induced monomeric ribosomes from the pea root was studied by varying the concentration of KCl (or NH(4)Cl) and MgCl(2) in the presence of dithiothreitol. These monoribosomes were shown to dissociate completely into subunits at 0.5m KCl or NH(4)Cl in the presence of 5 mm MgCl(2). The 40S subunits were more susceptible to structural change in KCl than were the 60S subunits. On the other hand, the 60S subunits appeared to be more labile to NH(4)Cl.The activity of the subunits relative to aminoacyl-tRNA binding and peptide bond formation was investigated using subunits derived from 0.5 m KCl (or NH(4)Cl) in the absence and presence of 5 mm MgCl(2). The 40S subunits were active in aminoacyl-tRNA binding only when dissociated in the presence of MgCl(2). The 40S and 60S subunits combined in the presence of poly U were active in incorporation of (14)C-phenylalanine from (14)C-phenylalanyl-tRNA only when dissociation was achieved in the presence of 5 mm MgCl(2). The KCl-dissociated subunits were much more active in protein synthesis than NH(4)Cl-dissociated subunits.

Journal Article↗
PubMed1971

Correlation between Polyribosome Level and the Ability to Induce Nitrate Reductase in Dark-grown Corn Seedlings.

Nitrate reductase can be induced in excised shoots of 3-day-old dark-grown Zea mays (var. WF9 x M14) seedlings in the absence of light. In contrast, leaves of 10-day-old dark-grown seedlings require a light treatment in order to induce enzymatic activity. Leaves of 10-day-old dark-grown seedlings contain a very low level of polyribosomes while 3-day-old shoots contain a very high level of polyribosomes. There is a gradual loss of polyribosomes from 3 to 10 days and a gradual loss of in vitro protein synthetic activity of the ribosome preparations. The loss of polyribosomes and decrease in their amino acid-incorporating activity correlate positively with the loss of ability to induce nitrate reducase activity as leaves of dark-grown corn seedlings age. These results corroborate and extend our previous results, in that light is not required for nitrate reductase induction per se in leaves of dark-grown seedlings but is required to reactivate the protein synthetic apparatus of older leaves.

Journal Article↗
PubMed1970

The Influence of Auxin and Ethylene on Chromatin-directed Ribonucleic Acid Synthesis in Soybean Hypocotyl.

Soybean seedlings treated with ethylene exhibited small increases in ribonucleic acid content in the elongating section of the hypocotyl. Chromatin isolated from the elongating section of ethylene-treated seedlings showed a 35 to 60% increase in the capacity for RNA synthesis. The ethylene-induced response was saturated at 1 microliter/liter of ethylene and was fully expressed after 3 hours. Auxin caused marked accumulation of RNA and DNA in the elongating and basal tissue of the hypocotyl. Chromatin isolated from these auxin-treated tissues showed an 8- to 10- fold increase in RNA synthetic capacity as measured in vitro. Ethylene added with auxin reduced the auxin enhancement of nucleic acid synthesis in the elongating and basal tissues. Both ethylene and auxin treatment of the seedlings inhibited nucleic acid accumulation and chromatin activity in the apical tissue. Ethylene did not appear to mediate the auxin effects on nucleic acid synthesis in soybean hypocotyl with the possible exception of inhibition in the apical tissue.The RNA which was synthesized by chromatin isolated from control and auxin- and ethylene-treated tissues was characterized by nearest neighbor analyses. The nearest neighbor frequencies of the RNA products synthesized by chromatin isolated from auxin- and ethylene-treated hypocotyl tissue were different from each other and different from the control RNA product.Seedlings treated in sealed containers exhibited growth, RNA, and DNA responses, especially to ethylene, different from those of seedlings treated in continuous flow containers.

Journal Article↗
PubMed1970

The fractionation of transfer ribonucleic Acid from roots of pea seedlings.

Isoaccepting transfer RNA species for several amino acids were fractionated by reverse phase column chromatography. Transfer RNA from dividing cells of pea (Pisum sativum) root was compared to that from nondividing cells, and no relative quantitative or qualitative differences were noted for the transfer RNA species for leucine, lysine, proline, threonine, methionine, serine, and phenylalanine. However, certain artifactual differences for serine and phenylalanine were noted. Quantitative differences were observed in tyrosyl-transfer RNA's. Ribonuclease action on tRNA did not contribute to the tRNA species observed.

Journal Article↗
PubMed1969

Hormonal regulation of cell elongation in the hypocotyl of rootless soybean: an evaluation of the role of DNA synthesis.

A method was developed where soybean seedlings were grown without roots to study the influence of hormones of root origin on shoot growth. Excision of the root resulted in inhibition of apical section growth and DNA synthesis and inhibited elongating section growth. A synthetic cytokinin restored DNA synthesis in the apical section, but did not influence growth in either the apical or elongating sections. Low concentrations of gibberellin with the cytokinin restored growth in the apical section. Gibberellin alone was sufficient to restore growth in the elongating section. An inhibitor of DNA synthesis, 5-fluorodeoxyuridine, inhibited the increase in apical section DNA without inhibiting control or gibberellin-induced growth in the elongating section. Experiments with (14)C-thymidine resulted in no DNA labeling differences in the elongating section under conditions where gibberellin-induced elongation varied from 50% to 73% above controls. It was concluded that gibberellin-induced elongation in soybean hypocotyl occurred in the absence of DNA synthesis. Gibberellin does stimulate DNA synthesis in the apical tissue apart from its effect on cell elongation. Excised soybean hypocotyl elongated maximally at 10(-6)m auxin. At higher auxin concentrations, fresh weight and ethylene production increased, but elongation was reduced. Addition of GA to the higher auxin concentrations resulted in a 50% inhibition in auxin-induced ethylene production and resumption in maximal elongation. Added ethylene inhibited elongation 30% at 2 mul/l. Addition of up to 100 mul/l ethylene did not inhibit elongation with GA present in the incubation medium. Thus GA may counteract ehtylene inhibition of cell elongation in addition to inhibiting ethylene production in auxin-treated tissues.

DNA↗
PubMed1968

A detailed evaluation of the possible contribution of bacteria to radioactive precursor incorporation into nucleic acids of plant tissues.

An investigation of the possible contribution of bacteria to the labeling patterns of soybean seedling nucleic acid was made. The results using sucrose gradient, MAK column, and acrylamide gel electrophoretic fractionation together with base composition analyses of nucleic acid preparations show that contaminating bacteria do not contribute to the incorporation of (32)P-orthophosphate into the RNA of excised hypocotyl or soybean root tip. Sterile, non-sterile, and CM-treated soybean hypocotyl synthesize D-RNA to the same extent. The contaminating bacteria do not synthesize an AMP-rich RNA. The G-C rich (32)P-DNA component of the soybean tissues used in these studied results, at least primarily, from the incorporation by contaminating bacteria. CM can be used successfully to eliminate the contribution of bacteria to the labeling of nucleic acids by etiolated plant tissues. Bacterial counts, although valuable, are not sufficient to determine if contaminating bacteria will significantly contribute to nucleic acid labeling in plants.

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