Preventing photochemistry in culture media by long-pass light filters alters growth of cultured tissues

Exposure of plant tissue culture media to light from fluorescent bulbs changed the growth regulating properties of the media. The light caused nutrient medium-dependent photosensitized degradation of the phytohormone indole-3-acetic acid and other media components. Photochemical changes in culture media were caused by light from 290 to 450 nanometers and were prevented with a yellow long-pass filter. The use of appropriately filtered light when culturing plant material can eliminate unnecessary variability by stabilizing the culture media composition.     

Detection of two loci involved in (1-->3)-beta-glucan (curdlan) biosynthesis by Agrobacterium sp. ATCC31749, and comparative sequence analysis of the putative curdlan synthase gene

Genes essential for the production of a linear, bacterial (1-->3)-beta- glucan, curdlan, have been cloned for the first time from Agrobacterium sp. ATCC31749. The genes occurred in two, nonoverlapping, genomic fragments that complemented different sets of curdlan( crd )-deficient transposon-insertion mutations. These were detected as colonies that failed to stain with aniline blue, a (1-->3)-beta-glucan specific dye. One fragment carried a biosynthetic gene cluster (locus I) containing the putative curdlan synthase gene, crdS, and at least two other crd genes. The second fragment may contain only a single crd gene (locus II). Determination of the DNA sequence adjacent to several locus I mutations revealed homology to known sequences only in the cases of crdS mutations. Complete sequencing of the 1623 bp crdS gene revealed highest similarities between the predicted CrdS protein (540 amino acids) and glycosyl transferases with repetitive action patterns. These include bacterial cellulose synthases (and their homologs), which form (1-->4)-beta-glucans. No similarity was detected with putative (1-->3)- beta-glucan synthases from yeasts and filamentous fungi. Whatever the determinants of the linkage specificity of these beta-glucan synthases might be, these results raise the possibility that (1-->3)-beta-glucans and (1-->4)-beta-glucans are formed by related catalytic polypeptides.      

Effect of fe-catalyzed photooxidation of EDTA on root growth in plant culture media

Light from fluorescent lamps can induce formaldehyde production and iron deficiency in plant nutrient culture medium. Formaldehyde is produced from EDTA when it is oxidized by the photochemical reduction of ferric iron and it can accumulate to inhibitory levels. The medium becomes iron deficient because iron becomes unchelated and forms an unavailable precipitate as EDTA is oxidized. The combination of light-induced formaldehyde production and loss of available iron reduces the ability of the culture media to support growth of Arabidopsis thaliana roots. Removing ultraviolet and blue wavelengths with a yellow acrylic filter is a simple and effective means of preventing Fecatalyzed photooxidation of EDTA in plant culture media.     

The relationship between the prothrombin upstream sequence element and the G20210A polymorphism: the influence of a competitive environment for mRNA 3'-end formation

The human prothrombin G20210A polymorphism located at the 3′ cleavage site of the mRNA results in elevated plasma prothrombin levels and increased risk of venous thrombosis. This polymorphism has been shown to directly influence a variety of processes related to prothrombin mRNA metabolism. We have constructed plasmids that express the full-length prothrombin mRNA that is polyadenylated at its natural site. The A allele prothrombin variant was more efficient than the G allele at promoting cleavage at this site in the presence of a competing poly (A) sequence. In the absence of competition, both allelic variants give rise to a similar level of cleavage site heterogeneity. An upstream sequence element (USE) was also identified within the prothrombin 3′-UTR. When placed upstream of two competing poly (A) sites, the USE directed cleavage preferentially to the proximal poly (A) site. In the absence of competition, the USE had no effect on cleavage site selection. This study suggests that the basis for the increase in prothrombin expression in A allele carriers is not due to allelic changes in cleavage site selection per se. In addition, the functionality of USEs needs to be considered within the context of endogenous sequence architecture.     

Inhibition of fungal exopolysaccharide production by chemical antifoams

Attempts to control foam production in exopolysaccharide synthesising cultures of Acremonium persicinum in aerobic fermentation with polypropylene glycol (PPG) 2025 led to a marked reduction in yield. Similar effects were seen with polysaccharide producing cultures of Epicoccum purpurascens , but not with Aureobasidium pullulans. The effects of other chemical antifoams on polysaccharide production in A. persicinum were examined, and no inhibition was noticed with any silicone-based compound.