Hormonal factors controlling the initiation and development of lateral roots

As the first part of a comprehensive study of the hormonal control of lateral root initiation and development, the effect of surgical treatments such as removal of the root tip, one or more cotyledons, the young epicotyl, or combination of these treatments, on the induction and emergence of lateral roots on the primary root of pea seedlings has been examined. Results show that removal of the root tip leads to a rapid but transitory increase in the number of lateral primordia, the largest number arising in the most apical segment of decapitated roots suggesting the accumulation of acropetally moving promoter substances in this region. The cotyledons appear to be the main source of promoter substances for both the induction and emergence of lateral roots, although one or more promoters also appear to be produced in the epicotyl. The data further indicate that the root tip is possibly the source of a substance which moves basipetally and interacts with acropetally moving promoters to regulate the zone for lateral primordia initiation; the root tip also appears to be the source of a powerful inhibitor of lateral root emergence.     

A lamB expression plasmid for extending the host range of phage λ to other enterobacteria

Abstract We have constructed a multicopy plasmid vector (pAMH62) expressing lamB , the gene coding for the phage λ receptor protein in Escherichia coli . In this construction, the lamB structural gene was fused to the ompR promoter of E. coli . The ompR promoter was employed because: (i) it can function in other gram negative bacteria; (ii) it expresses lamB in a multicopy state at a level comparable to that of maltose-induced chromosomal lamB in E. coli . The vector pAMH62 was tested in E. coli and Salmonella typhimurium . In both cases the LamB protein was produced in similar amounts, was properly integrated to the outer membrane and was functional as phage λ receptor. Thus pAMH62 should provide a useful tool for extending the host range of phage λ and λ-derived vectors to other Gram-negative bacteria.     

Xylarianaphthol-1, a novel dinaphthofuran derivative,activates p21 promoter in a p53-independent manner

Xylarianaphthol-1, a novel dinaphthofuran derivative, was isolated from a marine sponge-derived fungus of order Xylariales on the guidance of a bioassay using the transfected human osteosarcoma MG63 cells (MG63^luc+). The chemical structure of xylarianaphthol-1 was determined from the ¹H and ¹³C NMR analysis and was further confirmed by the total synthesis. Xylarianaphthol-1 activated p21 promoter stably transfected in MG63 cells dose-dependently. Expression of p21 protein in the wild-type MG63 cells was also increased by xylarianaphthol-1 treatment.     

Intrinsic Bent DNA Sites in the Developmentally Amplified C3-22 Gene Promoter of Rhynchosciara americana (Diptera: Sciaridae)

The Rhynchosciara americana C3-22 gene is located in an amplified domain and is developmentally expressed. The aim of the present work was to identify intrinsically bent DNA sites in a segment containing the gene promoter and downstream sequence. The results indicated that this gene is flanked by intrinsically bent DNA sites. Three bent DNA sites (b^?3, b^?2, and b^?1) were localized in the promoter, and one was localized downstream of the gene (b⁺¹). These sites had helical parameters that confirmed the curved structure, as well as segments with left-handed superhelical writhe. In silico analysis of the promoters of four other insect genes, which encode secreted polypeptides, showed that they all had curved structures and similar helical parameters. Correlation with other results indicates that the detected intrinsically bent DNA sites that flank the C3-22 gene might be a consensus feature of the gene structure in the amplified domains.     

Food-Grade Expression and Characterization of a Dextranase from Chaetomium gracile Suitable for Sugarcane Juice Clarification

The microbial production of dextranase using cheap carbon sources is beneficial to solve the economic loss caused by the accumulation of dextran in syrup. A food-grade microbial cell factory was constructed by introducing the dextranase encoding gene DEX from Chaetomium gracile to the chromosome of Bacillus subtilis, and the antibiotic resistance marker gene was subsequently deleted via the Cre/loxP strategy. The dual-promoter system with a sequentially arranged constitutive P43 promoter resulted in an 85 % increase in DEX expression. Under the optimal fermentation conditions of 10 g/L maltose, 15 g/L casein, 1 g/L Na₂HPO₄, 1 g/L FeSO₄ and 8 g/L NaCl, DEX activity was increased from 2.625 to 64.34 U/mL. Recombinant DEX was purified 5.98-fold with a recovery ratio of 26.67 % and specific activity of 3935.02 U/mg. Enzyme activity was optimal at 55 °C and pH 5.0 and remained 80.34 % and 71.36 % of the initial activity at 55 °C and pH 4.0 after 60 min, respectively. The enzyme possessed high activity in the presence of Co²⁺, while Ag⁺ showed the strongest inhibition ability. The optimal substrate was 20 g/L dextran T-2000. The findings could facilitate the low-cost, large-scale production of food-grade DEX for use in the sugar industry.