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.     

Enzymic synthesis,chemical characterisation and Sda activity of GalNAcß1-4[NeuAcα2-3]Galß1-4GlcNAc and GalNAcß1-4[NeuAcα2-3]Galß1-4Glc

The tetrasaccharides GalNAcß1-4[NeuAc2-3]Galß1-4Glc and GalNAcß1-4[NeuAc2-3]Galß1-4GlcNAc were synthesised by enzymic transfer of GalNAc from UDP-GalNAc to 3-sialyllactose (NeuAc2-3Galß1-4Glc) and 3-sialyl-N-acetyllactosamine (NeuAc2-3Galß1-4GlcNAc). The structures of the products were established by methylation and¹H-500 MHz NMR spectroscopy. In Sd^a serological tests the product formed with 3-sialyl-N-acetyllactosamine was highly active whereas that formed with 3-sialyllactose had only weak activity.     

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.     

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.     

Approaches to breeding for salinity tolerance - a case study on Porteresia coarctata

Cereals are the world's major source of food for human nutrition. Among these, rice (Oryza sativa) is the most prominent and represents the staple diet for more than two-fifths (2.4 billion) of the world's population, making it the most important food crop of the developing world (Anon., 2000a). Rice production in vast stretches of coastal areas is hampered due to high soil salinity. This is because rice is a glycophyte and it does not grow well under saline conditions. In order to increase rice production in these areas there is a need to develop rice varieties suited to saline environments. Research has shown that Porteresia coarctata, a highly salt tolerant wild relative of rice growing in estuarine soils, is an important material for transferring salt tolerant characteristics to rice. It is quite possible that Porteresia may be used as a parent for evolving better and truly salt resistant varieties. The inadequate results and the difficulties associated with conventional breeding techniques necessitate the use of the tools of crop biotechnology in unravelling some of the characteristics of Porteresia that have been highlighted in this report. In view of the limited resources available for increasing salinity tolerance to the breeders to wild rice germplasm, Porteresia is undoubtedly one of the key source species for elevating salinity tolerance in cultivated rice.     

Variables in the high-pressure cation-exchange chromatography of proteins

The use of cation-exchange high-pressure liquid chromatography for the separation of proteins has been investigated. Several factors, including solvent composition, pH, flow rate, and temperature, were examined for their effects on the resolution of protein standards (insulin, β-lactoglobulin, and carbonic anhydrase B; molecular weight range, 6000 to 30,000 and pI range, 5.3 to 6.5). An initial comparison was made of the recovery of these proteins from three commercially available columns (Whatman Partisil SCX, Separation Industry CM silica, and MCB Reagents Lichrosorb KAT). In general, under the conditions employed, the SCX column gave the highest recovery of applied protein. Based on this recovery data, the Partisil SCX column was chosen for subsequent examination of chromatographic parameters that would optimize protein resolution. An increase in temperature decreased retention and resolution but increased recovery, with some proteins being affected more than others. A decrease in pH in the final eluant or an increase in pH in the initial eluant caused an increase in retention times. For some proteins, the decrease in pH resulted in a greater total recovery of protein. This information has been applied to the purification by cation-exchange high-pressure liquid chromatography of transforming growth factors from a human tumor cell line.