Periodicity of bud bursting in willow (Salix viminalis) as affected by growth regulators

Saunders, P. F. and Barros, R. S. 1987. Periodicity of bud bursting in willow ( Salix viminalis ) as affected by growth regulators.
Lateral vegetative buds of willow ( Salix viminalis L.) were only innately dormant for 3–5 weeks in October; during this time their apices were correlatively inhibited by the bud leaflets. Exogenous gibberellins stimulated the opening of cultured buds when the plants were dormant or entering dormancy. As dormancy was being released, however, cultured buds became more responsive to exogenous cytokinins. Thus the demand for gibberellins and cytokinins for bud opening seemed to be sequential rather than simultaneous. Dormant buds cultured in the presence of abscisic acid remained unopened, but they opened after a chilling treatment. Subsequent growth of such buds as measured by dry matter accumulation, was observed only if a cytokinin was added to the medium.     

To produce many small or few large eggs: a size-independent reproductive tactic of fish

Summary We demonstrate here the existence of a range of size-independent reproductive tactics in teleostean fish involving the allocation of a size-dependent reproductive effort between fecundity and egg size. Despite considerable evidence that larger eggs and the larvae hatching from them are more likely to survive than smaller ones, we found no evidence of evolutionary trends towards greater egg sizes. Fish with pelagic eggs tend to spawn many, and therefore small, eggs, whereas demersal spawners tend to produce large, and therefore few, eggs. Maximizing egg number should increase the number of eggs hatching in suitable locations in the patchy pelagic environment and, hence, increase the reproductive success of pelagic spawners. On the other hand, the reproductive success of demersal spawners, which reduce the variance in growing conditions experienced by the off spring, should be more dependent on the survival of the individual larvae, which increases as egg size increases.     

Bacterial Metabolism of 2,6-Xylenol

Strain DM1, a Mycobacterium sp. that utilizes 2,6-xylenol, 2,3,6-trimethylphenol, and o-cresol as sources of carbon and energy, was isolated. Intact cells of Mycobacterium strain DM1 grown with 2,6-xylenol cooxidized 2,4,6-trimethylphenol to 2,4,6-trimethylresorcinol. 4-Chloro-3,5-dimethylphenol prevents 2,6-xylenol from being totally degraded; it was quantitatively converted to 2,6-dimethylhydroquinone by resting cells. 2,6-Dimethylhydroquinone, citraconate, and an unidentified metabolite were detected as products of 2,6-xylenol oxidation in cells that were partially inactivated by EDTA. Under oxygen limitation, 2,6-dimethylhy-droquinone, citraconate, and an unidentified metabolite were released during 2,6-xylenol turnover by resting cells. Cell extracts of 2,6-xylenol-grown cells contained a 2,6-dimethylhydroquinone-converting enzyme. When supplemented with NADH, cell extracts catalyzed the reduction of 2,6-dimethyl-3-hydroxyquinone to 2,6-dimethyl-3-hydroxyhydroquinone. Since a citraconase was also demonstrated in cell extracts, a new metabolic pathway with 2,6-dimethyl-3-hydroxyhydroquinone as the ring fission substrate is proposed.     

Comparison between intra- and extracellular surfactant in respiratory distress induced by oleic acid

The present study compares the phospholipid distribution and protein content in bronchoalveolar lavage, purified extracellular surfactant and lamellar bodies isolated from rabbits killed at intervals of 2.5, 12 and 24 h after oleic acid administration. The data suggest that the alteration of pulmonary surfactant could be partially due to the type II cell response to the injury.     

Mechanisms of degradation of 2′-5′ oligoadenylates

We have studied the mechanisms of breakdown of 2'-5' oligoadenylates. We monitored the time-courses of degradation of ppp(A2'p5')nA (dimer to tetramer) and of 5'OH-(A2'p5')nA (dimer to pentamer) in unfractionated L1210 cell extract. The 5' triphosphorylated 2'-5' oligoadenylates are converted by a phosphatase activity. However, 2'-5' oligoadenylates are degraded mainly by phosphodiesterase activity which splits the 2'-5' phosphodiester bond sequentially at the 2' end to yield 5' AMP and one-unit-shorter oligomers. The nonlinear least-squares curve-fitting program CONSAM was used to fit these kinetics and to determine the degradation rate constant of each oligomer. Trimers and tetramers, whether 5' triphosphorylated or not, are degraded at the same rate, whereas 5' triphosphorylated dimer is rapidly hydrolyzed and 5'-OH dimer is the most stable oligomer. The interaction between degradation enzymes and the substrate strongly depends on the presence of a 5' phosphate group in the vicinity of the phosphodiester bond to be hydrolyzed; indeed, when this 5' phosphate group is present, as in pp/pA2'p5'A/or A2'/p5'A2'p5'A/, affinity is high and maximal velocity is low. Such a degradation pattern can control the concentration of 2'-5' oligoadenylates active on RNAse L either by limiting their synthesis (5' triphosphorylated dimer is the primer necessary for the formation of longer oligomers) and/or by converting them into inhibitory (e.g., monophosphorylated trimer) or inactive (e.g., nonphosphorylated oligomers) molecules.     

Tremorgenic mycotoxins produced by strains of Penicillium spp. isolated from toxic Poa huecu parodi

Seventeen strains of Penicillium spp. have been isolated from Poa huecu Parodi from the Zapala zone, exhibiting toxicity to sheet. The following strains have been identified: P. crustosum, cyclopium, notatum, palitans, puberulum, verrucosum, viridicatum and Penicillium spp. The toxigenic capacity of the strains was studied after growing them under suitable conditions. Toxins produced were analysed by thin layer chromatography (TLC). Penitrem A (PA) and Penitrem B (PB) neurotoxins were identified and quantitated in twelve strains; verruculogen (VERR) and fumitremorgen B (FTB) being present in one of them. The effect of these mycotoxins was studied in mice. Neurological symptoms characteristic of the intoxication by tremorgenic toxins and similar to those observed in sheep suffering from huecu's disease were observed. The possible role of these toxins as causative agents of huecu's disease is discussed.     

Isolation and genetic structure of IS112, an insertion sequence responsible for the inactivation of the SalI restriction-modification system of Streptomyces albus G.

Summary IS112 is a transposable element identified in Streptomyces albus G by its frequent mutagenic insertion into the genes for the SalI restriction-modification system. IS112 is present in several copies in the genome of S. albus G. Homologous sequences were detected in other Streptomyces strains. Sequence analysis revealed that IS112 has a length of 883 by with a GC content of 67.4%. The copy that was isolated contained imperfect inverted repeats (16/20 match) at its ends and was flanked by a 2 by duplication at the target site, which was located within the gene (salIR) for the Sall endonuclease. A long open reading frame (ORF) encoding a putative polypeptide of 256-253 amino acids spans almost the entire sequence. Significant homology was detected between this polypeptide and that corresponding to ORFB of IS493, an insertion sequence recently isolated from Streptomyces lividans 66.

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Cis-analysis of a seed protein gene promoter: the conservative RY repeat CATGCATG within the legumin box is essential for tissue-specific expression of a legumin gene

A 2.4 kb fragment containing the 5'-flanking region and the 5'-noncoding sequence of the Vicia faba legumin gene LeB4 mediates high level seed-specific expression in transgenic tobacco plants. Deleted derivatives of this legumin upstream sequence were fused to the npt-II reporter gene to determine the tissue-specific activity of the chimeric constructs in stably transformed tobacco plants. The results indicate the presence of positive regulatory, enhancer-like cis elements within 566 bp of the upstream sequence. Most importantly, however, these elements are only fully functional in conjunction with the core motif CATGCATG of the legumin box around position -95, since destruction of the motif by a 6 bp deletion in an otherwise intact 2.4 kb upstream sequence drastically reduces expression in seeds. At the same time, low level expression in leaves is observed. The occurrence of similar CATGCATG consensus cis elements with alternating purine and pyrimidine base pairs in front of several other plant genes suggests a functional role of the motif in a wider range of plant promoters.