ABSTRACT
Effects of supplemented UV radiation and diminished water supply on the leaf concentrations of phenols and antioxidants of two Mediterranean resprouter species, Arbutus unedo and Quercus suber, were assessed before and after entire aerial biomass removal. Potted seedlings of both species were grown outdoors for 8 months with enhanced UV-A + UV-B, enhanced UV-A or ambient UV, in combination with two watering conditions (field capacity or watering reduction). After this period, all aerial biomass was removed and new shoots (resprouts) developed for a further 8 months under the two treatments. In general, the investment in leaf phenols was substantially greater in A. unedo than in Q. suber, while Q. suber allocated more resources to non-phenolic antioxidants (ascorbate and glutathione). In response to enhanced UV-B radiation, Q. suber leaves rose their UV-screening capacity mainly via accumulation of kaempferols, accompanied by an increased concentration of rutins, being these effects exacerbated under low-watering conditions. Conversely, A. unedo leaves responded to UV-B radiation reinforcing the antioxidant machinery by increasing the overall amount of flavonols (especially quercetins) in seedlings, and of ascorbate and glutathione, along with catalase activity, in resprouts. Nevertheless, UV effects on the amount/activity of non-phenolic antioxidants of A. unedo resprouts were modulated by water supply. Indeed, the highest concentration of glutathione was found under the combination of enhanced UV-B radiation and reduced watering, suggesting an enlargement of the antioxidant response in A. unedo resprouts. Different biochemical responses to enhanced UV and drier conditions in seedlings and resprouts of these two species might modulate their competitive interactions in the near future.
Subject(s)
Ericaceae/metabolism , Phenols/metabolism , Plant Leaves/metabolism , Quercus/metabolism , Antioxidants/metabolism , Ascorbic Acid/metabolism , Ericaceae/radiation effects , Glutathione/metabolism , Mediterranean Region , Plant Components, Aerial , Plant Leaves/radiation effects , Quercus/radiation effects , Seedlings/radiation effects , Ultraviolet Rays , WaterABSTRACT
A series of 3-fluoro-1-aza- and 1,8-diazaanthraquinones, structurally related to the antitumour antibiotic diazaquinomycin A, have been prepared by Diels-Alder reactions of 2-fluoro-2-propenal N, N-dimethylhydrazone and the corresponding quinones. These compounds showed potent in vitro activity against different tumour cell lines. They also showed some selectivity towards rapid-growth tumours when compared to other non-fluorinated analogues. In contrast with diazaquinomycin A, the azaanthraquinones studied here have not shown significant activity as thymidylate synthase inhibitors. Some compounds showed a high activity as inhibitors of protein, DNA and RNA biosynthesis.
Subject(s)
Antineoplastic Agents/chemical synthesis , Animals , Antineoplastic Agents/pharmacology , DNA/biosynthesis , Drug Screening Assays, Antitumor , Humans , Magnetic Resonance Spectroscopy , Mice , Protein Synthesis Inhibitors/chemical synthesis , Protein Synthesis Inhibitors/pharmacology , RNA/biosynthesis , Spectrophotometry, Infrared , Thymidylate Synthase/antagonists & inhibitors , Tumor Cells, CulturedABSTRACT
Microcin C7 (MccC7) is encoded by Escherichia coli plasmid pMccC7. However, some strains of E. coli K-12 carrying this plasmid do not produce this antibiotic. Here we show that these strains differ in the gene locus appR. This chromosomal gene product controls MccC7 production by activating the transcription of some, but not all, MccC7 plasmid genes.
Subject(s)
Bacteriocins/genetics , Escherichia coli/genetics , Genes, Bacterial , Plasmids , Transcription Factors/genetics , Transcription, Genetic , Gene Expression RegulationABSTRACT
Microcin C7, a peptide antibiotic inhibitor of protein synthesis, is produced by Escherichia coli K-12 strains that carry the 43-kilobase low-copy-number plasmid pMccC7. Microcin C7 production and immunity determinants of this plasmid have been cloned into the vectors pBR322 and pACYC184. The resulting plasmids overproduce microcin C7 and express immunity against the microcin. Mcc- and Mcc- Imm- mutants have been isolated on recombinant plasmids by inserting transposable elements. Physical and phenotypic characterization of these mutants shows that a DNA region of 5 kilobases is required to produce microcin C7, and that two small regions located inside the producing region are also required to express immunity. Analysis of plasmids carrying mcc-lacZ gene fusions indicates that all microcin DNA is transcribed in the same direction. The results suggest that a structure like a polycistronic operon is responsible for microcin C7 production and immunity.
