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Biomedical subjects

J L Key

Publications and source records attributed to J L Key.

104 records · Page 6Linked to original sources
PubMed1967

Inactive and protein precursor pools of amino acids in the soybean hypocotyl.

There are at least 2 amino pools for leucine and for valine in the soybean hypocotyl, a small protein precursor pool and a large inactive pool. The precursor pool decreased in size during incubation of excised hypocotyls presumably because the cotyledonary sources of amino acids had been removed. The precursor pool was subject to expansion by supplying the amino acid externally at high concentrations. After the transfer of tissue to unsupplemented media, the expanded pool was rapidly depleted.

Journal Article↗
PubMed1967

Inhibition of RNA synthesis and auxin-induced cell wall extensibility and growth by Actinomycin D.

A linear stress strain analyzer was used to determine the effects of inhibitors of RNA and protein synthesis on auxin-induced increases in cell wall extensibility. With etiolated soybean hypocotyl, maize mesocotyl and Avena coleoptile sections and light-grown pea internode sections, inhibition of RNA synthesis resulted in inhibition of auxin-induced extensibility changes and cell expansion. The results with both actinomycin D and cycloheximide support an earlier conclusion that unstable cell constituents, presumably enzymes, are essential for cell wall loosening induced by auxin as well as for cell elongation.

Cell Wall↗
PubMed1967

Absence of a Causal Relationship between Auxin-Induced Growth and Changes in the Content of Ascorbic and Dehydroascorbic Acids in Excised Plant Tissues.

The data reported indicate that the oxidation-reduction balance of the ascorbic acid system is not causally related to the auxin-regulation of cell elongation. There was no shift in the ascorbic acid (AA) to dehydroascorbic acid (DHA) ratio with growth-promoting concentration of auxin in several plant tissues. The AA to DHA ratio was experimentally increased without altering the growth rate. Inhibition of growth by supra-optimal auxin was associated with a decrease in the AA to DHA ratio. Since the AA to DHA ratio was lowered by EDTA treatment without altering growth, it seems unlikely that the decrease in the AA to DHA ratio related to the inhibition of growth by high levels of auxin.

Journal Article↗
PubMed1966

Association of D-RNA with Polyribosomes in the Soybean Root.

Ribosomes from soybean root tips were shown to consist of about 75% polyribosomes based on size distribution on sucrose gradients. Electronmicrographs showed the presence of ribosome clusters in normal preparations and only monomers and dimers in ribonuclease-treated preparations. The polyribosome preparations, but not single ribosomes, showed good in vitro amino acid incorporating activity.D-RNA was associated with the ribosome preparations, and preferentially in the polyribosome structure. It is suggested that at least a part of the soybean D-RNA represents a class of messenger RNA.

Journal Article↗
PubMed1966

Effect of purine and pyrimidine analogues on growth and RNA metabolism in the soybean hypocotyl-the selective action of 5-fluorouracil.

The effects of several base analogues and cycloheximide on RNA synthesis, protein synthesis, and cell elongation were studied in excised soybean hypocotyl. None of the pyrimidine analogues tested affected growth or protein synthesis; only 5-fluorouracil appreciably inhibited RNA synthesis. 8-Azaguanine and 6-methylpurine markedly inhibited RNA and protein synthesis and cell elongation. Cycloheximide effectively inhibited both cell elongation and protein synthesis. The results show that 5-fluorouracil selectively inhibited ribosomal and soluble RNA synthesis without affecting the synthesis of D-RNA. These results indicate that the requirement for RNA synthesis to support continued protein synthesis and cell elongation is restricted to the synthesis of D-RNA.5-Fluorouracil was incorporated into all classes of RNA in a form believed to be 5-fluorouridylic acid. Cycloheximide markedly inhibited the accumulation of ribosomal RNA, but the results indicate that CH did not inhibit, per se, the synthesis of ribosomal RNA. The accumulation of newly synthesized D-RNA was only slightly affected by cycloheximide. These results show that the inhibition of cell elongation by cycloheximide correlates with the inhibition of protein synthesis, but not with the effect on RNA metabolism.

Cycloheximide↗
PubMedDate not supplied

Modulation of gene expression by auxin.

Auxin, a class of plant hormones which affects a wide array of growth and developmental processes including cell elongation and cell division, alters gene expression in a very rapid, selective, and dramatic way. The relative level of some mRNAs decreases several fold, while that of other mRNAs increases many fold. These changes are mediated, at least in some cases, by very fast (within 5-10 min) modulation by auxin of transcription as measured by run-off transcription assays using nuclei isolated from control and auxin-treated tissues. Rapid turnover of mRNAs following auxin treatment also contributes to large changes in steady state concentration in some cases. The data are suggestive of multiple and complex mechanisms of regulation of expression of those genes which have been studied, using cloned cDNAs for direct quantitation of mRNA steady state levels and relative transcription rats. While there is no definitive evidence that auxin-regulated gene expression mediates any of the growth responses effected by auxin, several lines of evidence are supportive of a very close relationship between these processes. The working hypothesis is that there is a causal relationship between the effects of auxin on gene expression and at least some of the physiological and growth responses to auxin.

Amino Acid Sequence↗