Dimerization of 2,6-dimethoxyphenol by Aspergillus flavus: evidence for the reaction occurring close to mycelia

Aspergillus flavus grown on 2,6-dimethoxyphenol as sole carbon source produced tetramethoxy-p-dibenzoquinone by a free radical mechanism. The product was identified by H-nmr and ms. Scanning electron microscopy and light microscopy were used to follow the growth of mycelia and the attachment of crystals to the mycelial surfaces. Formation of dimer was inhibited by the presence of glucose in the medium.     

Evolutionary conservation of the chromosomal configuration and regulation of amylase genes among eight species of the Drosophila melanogaster species subgroup

Nuclear DNA was extracted from each of the eight species comprising the Drosophila melanogaster species subgroup. Southern hybridization of this DNA by using a molecular probe specific for the alpha-amylase coding region showed that the duplicated structure of the amylase locus, first found in D. melanogaster, is conserved among all species of the melanogaster subgroup. Evidence is also presented for the concerted evolution of the duplicated genes within each species. In addition, it is shown that the glucose repression of amylase gene expression, which has been extensively studied in D. melanogaster, is not confined to this species but occurs in all eight members of the species subgroup. Thus, both the duplicated gene structure and the glucose repression of Drosophila amylase gene activity are stable over extended periods of evolutionary time.      

Genotype dependent variation in mycorrhizal colonization and response to inoculation of pearl millet

Summary Genotypes of pearl millet (Pennisetum americanum L. Leeke) were examined for differences in vesicular-arbuscular mycorrhizal (VAM) colonization and response to inoculation. For thirty genotypes tested across three field locations there was a range of mycorrhizal colonization intensity between 25 and 56%. In another experiment with two male-sterile lines, restorer lines and their derived crosses, grown in pots filled with non-sterilized soil there were significant differences between genotypes for colonization by mycorrhiza. This showed hostgenotype dependence for mycorrhizal colonization.Root growth rates, mycorrhizal root length, percentage root colonization and plant growth and P uptake were studied in ten genotypes. A set of 3 genotypes with similar root lengths varied significantly with regard to mycorrhizal root length and the percentage colonization. This supports the suggestion that VAM colonization and spread is dependent on the host genotype. The growth responses differed significantly between the genotypes and they also differed in their responses to P uptake and VAM inoculation. The utility of host-genotype dependent differences in VAM symbiosis in plant breeding is discussed.Journal Article No. 453     

Immunodetection and quantitation of the two forms of transforming growth factor-beta (TGF-beta 1 and TGF-beta 2) secreted by cells in culture

Transforming growth factor beta (TGF-beta), a potent modulator of cell growth, differentiation, and the expression of extracellular matrix components in a variety of cell types, exists as two distinct homodimers (TGF-beta 1 and TGF-beta 2), sharing 71% sequence homology. Radioreceptor and previously described radioimmunological assays using rabbit antibodies have not been able to distinguish between these two forms. We have developed antisera in turkeys against native TGF-beta 1 and TGF-beta 2, each of which specifically blocks both the receptor binding and biological activity of each of these peptides. With these immunological reagents we describe sensitive and specific immunological assays for TGF-beta 1 and TGF-beta 2 in complex biological fluids. Using these assays we show that both TGF-beta 1 and TGF-beta 2 are secreted by a variety of cultured cells, but that some cells secrete predominantly either TGF-beta 1 or TGF-beta 2 while others secrete both peptides in nearly equal amounts. Our results demonstrate that the expression of each of the two forms of TGF-beta is independently regulated.     

Growth of Phytomonas serpens in a Defined Medium; Nutritional Requirements

ABSTRACT. Three strains of Phytomonas serpens two from tomatoes, Lycopersicon esculentum one from the insect Phtia picta (Hemiptera, Coreidae), were cultivated in a chemically defined medium developed from a defined medium for cultivating insect flagellates. Besides organic growth factors required by other insect trypanosomatids this flagellate requires, serine and inositol. Glutamine stimulates growth, and, surprisingly, does not require heme.     

Sequence variation in the outer-surface-protein genes of Borrelia burgdorferi

Borrelia burgdorferi is a spirochete pathogen transmitted among warm- blooded hosts by ixodid ticks. Frequency-dependent selection for variant outer-surface proteins might be expected to arise in this species, since rare variants are more likely to avoid immune surveillance in previously infected hosts. We sequenced the OspA and OspB genes of nine North American strains and compared them with nine strains previously described. For each gene, the mean number of synonymous substitutions per synonymous site and the mean number of nonsynonymous substitutions per nonsynonymous site show only a twofold excess of silent mutations. Synonymous rates vary widely along the OspB protein. Some regions show a significant excess of silent substitutions, while divergence in other regions is constrained by biased base composition or selection. The presence, in antigenically important regions of the protein, of significant variation among strains, as well as evidence for recombination among strains, should be considered in attempts to develop vaccines against this disease.      

Pod development of groundnut (Arachis hypogaea L.) in solution culture

Normal pods (containing seed) of groundnut (Arachis hypogaea L.) (cv. TMV-2) were successfully raised in darkened, aerated, nutrient solution, but not in the light. The onset of podding was evident 7 to 8 d after gynophores were submerged in the darkened nutrient solution. An examination of pods and submerged portions of gynophore surfaces by scanning electron microscopy showed the presence of two distinctly different protuberances: unicellular root-hair-like structures that first developed from epidermal cells of the gynophores and developing pods; and branched septate hairs that developed later from cells below the epidermal layer. The septate hairs became visible only after the epidermal and associated unicellular structures had been shed by the expanding gynophore and pods. Omission of Mn and Mg from the podding environment increased pod and seed weight, whilst omission of Zn reduced pod and seed weight.     

Characterisation of a 34 kD protein from potato cyst nematodes, using monoclonal antibodies with potential for species diagnosis

Two monoclonal antibodies, which differentially recognise the two species of potato cyst nematodes (PCN), Globodera pallida and G. rostochiensis, are described. They have been shown to have potential for quantification of these two species, recognising proteins of the same molecular weight (34 kD) in both species. Further investigation showed these proteins to have isoelectric points at pH values of 5.7 in G. pallida and 5.9 in G. rostochiensis, in common with the proteins used by Fleming & Marks (1983) to differentiate the species of PCN. They are likely to be structurally very similar, with the same physiological function (and therefore similar concentrations) in the two species. In cross-reactivity tests with a wide range of soil nematode species, the antibodies reacted strongly only with species of the genus Globodera, and thereby confirmed their potential as the basis of a quantitative immunoassay likely to be useful in management of PCN populations.