The Extracellular Heme-binding Protein HbpS from the Soil Bacterium Streptomyces reticuli Is an Aquo-cobalamin Binder

The extracellular protein HbpS from Streptomyces reticuli interacts with iron ions and heme. It also acts in concert with the two-component sensing system SenS-SenR in response to oxidative stress. Sequence comparisons suggested that the protein may bind a cobalamin. UV-visible spectroscopy confirmed binding (K_d = 34 μm) to aquo-cobalamin (H₂OCbl⁺) but not to other cobalamins. Competition experiments with the H₂OCbl⁺-coordinating ligand CN⁻ and comparison of mutants identified a histidine residue (His-156) that coordinates the cobalt ion of H₂OCbl⁺ and substitutes for water. HbpS·Cobalamin lacks the Asp-X-His-X-X-Gly motif seen in some cobalamin binding enzymes. Preliminary tests showed that a related HbpS protein from a different species also binds H₂OCbl⁺. Furthermore, analyses of HbpS-heme binding kinetics are consistent with the role of HbpS as a heme-sensor and suggested a role in heme transport. Given the high occurrence of HbpS-like sequences among Gram-positive and Gram-negative bacteria, our findings suggest a great functional versatility among these proteins.     

Effect of chronically administered methylxanthines on ethanol-induced motor incoordination in mice

The effect of chronic (10 days) administration of methylxanthines, caffeine, IBMX and theophylline on acute ethanol-induced motor incoordination has been investigated in the mice. In animals that received caffeine, 45 and 90 mg/kg/24 h, ethanol, 1.5 g/kg, produced motor incoordination significantly greater compared to that in the control groups. Significantly greater ethanol-induced motor incoordination was seen in animals fed IBMX, 30 and 60 mg/kg/24 h, compared to controls. Ethanol-induced increased motor incoordination in caffeine and IBMX-fed animals was also associated with significantly greater 3H-R-PIA binding in whole brains compared to tap water controls indicating an increase in brain adenosine binding sites. However neither motor incoordination nor 3H-R-PIA binding was altered in theophylline 75 and 150 mg/kg/24 h, fed animals. The increased motor incoordination associated with increased adenosine binding sites in the brains of caffeine and IBMX-fed animals suggests an involvement of central adenosine mechanisms in the motor incoordinating effect of ethanol and further supports our earlier suggestion for the role of adenosine in some of the central effects of ethanol.     

Fungal growth promotor endophytes: a pragmatic approach towards sustainable food and agriculture

Agricultural productivity suffers a heavy loss due to plant pathogens, insect pests and various abiotic stresses. Agriculture being the world’s largest economic sector, it is the need of time to find and establish the ideal strategy for sustainable agriculture and improvement in crop growth. Endophytes are microorganisms that asymptomatically grow within the plant tissues without causing any disease to the host. Endophytic fungi live in symbiotic association with plants and play an important role in plant growth promotion, higher seed yield and plants resistant to various biotic, abiotic stresses and diseases. Many are able to produce antimicrobial compounds, plant growth hormones and various agrochemical bioactive metabolites. These mycoendophytes hold enormous potential for the development of eco-friendly and economically viable agricultural products. In this review we focused on the endophytic fungi recovered from different medicinal plants, their active principles involved in plant growth enhancement and the applications of fungal endophytes in agriculture. Moreover, we also discussed about endophytic fungi and their pragmatic approach towards sustainable food and agriculture.     

Improving the Effectiveness of Artificial MicroRNA (amiR)-Mediated Resistance against Turnip Mosaic Virus by Combining Two amiRs or by Targeting Highly Conserved Viral Genomic Regions

A drawback of recent antiviral therapies based on the transgenic expression of artificial microRNAs (amiRs) is the ease with which viruses generate escape mutations. Here, we show two alternative strategies for improving the effectiveness of resistance in plants. First, we expressed two amiRs complementary to independent targets in the viral genome, and second, we designed amiRs complementary to highly conserved RNA motifs in the viral genome.     

A gene required for very short patch repair in Escherichia coli is adjacent to the DNA cytosine methylase gene.

Deamination of 5-methylcytosine in DNA results in T/G mismatches. If unrepaired, these mismatches can lead to C-to-T transition mutations. The very short patch (VSP) repair process in Escherichia coli counteracts the mutagenic process by repairing the mismatches in favor of the G-containing strand. Previously we have shown that a plasmid containing an 11-kilobase fragment from the E. coli chromosome can complement a chromosomal mutation defective in both cytosine methylation and VSP repair. We have now mapped the regions essential for the two phenotypes. In the process, we have constructed plasmids that complement the chromosomal mutation for methylation, but not for repair, and vice versa. The genes responsible for these phenotypes have been identified by DNA sequence analysis. The gene essential for cytosine methylation, dcm, is predicted to code for a 473-amino-acid protein and is not required for VSP repair. It is similar to other DNA cytosine methylases and shares extensive sequence similarity with its isoschizomer, EcoRII methylase. The segment of DNA essential for VSP repair contains a gene that should code for a 156-amino-acid protein. This gene, named vsr, is not essential for DNA methylation. Remarkably, the 5' end of this gene appears to overlap the 3' end of dcm. The two genes appear to be transcribed from a common promoter but are in different translational registers. This gene arrangement may assure that Vsr is produced along with Dcm and may minimize the mutagenic effects of cytosine methylation.     

Application of Fluorescence Emission for Characterization of Albendazole and Ricobendazole Micellar Systems: Elucidation of the Molecular Mechanism of Drug Solubilization Process

Albendazole (ABZ) and ricobendazole (RBZ) are referred to as class II compounds in the Biopharmaceutical Classification System. These drugs exhibit poor solubility, which profoundly affects their oral bioavailability. Micellar systems are excellent pharmaceutical tools to enhance solubilization and absorption of poorly soluble compounds. Polysorbate 80 (P80), poloxamer 407 (P407), sodium cholate (Na-C), and sodium deoxycholate (Na-DC) have been selected as surfactants to study the solubilization process of these drugs. Fluorescence emission was applied in order to obtain surfactant/fluorophore (S/F) ratio, critical micellar concentration, protection efficiency of micelles, and thermodynamic parameters. Systems were characterized by their size and zeta potential. A blue shift from 350 to 345 nm was observed when ABZ was included in P80, Na-DC, and Na-C micelles, while RBZ showed a slight change in the fluorescence band. P80 showed a significant solubilization capacity: S/F values were 688 for ABZ at pH 4 and 656 for RBZ at pH 6. Additionally, P80 micellar systems presented the smallest size (10 nm) and their size was not affected by pH change. S/F ratio for bile salts was tenfold higher than for the other surfactants. Quenching plots were linear and their constant values (2.17/M for ABZ and 2.29/M for RBZ) decreased with the addition of the surfactants, indicating a protective effect of the micelles. Na-DC showed better protective efficacy for ABZ and RBZ than the other surfactants (constant values 0.54 and 1.57/M, respectively), showing the drug inclusion into the micelles. Entropic parameters were negative in agreement with micelle formation.     

Adenine type and diphenyl urea derived cytokinins improve the postharvest performance of <Emphasis Type="Italic">Iris germanica</Emphasis> L. cut scapes

An experiment was designed to evaluate the effect of various adenine derived cytokinins (kinetin and 6-benzylaminopurine) and diphenyl urea cytokinin (thidiazuron) on the postharvest performance of cut scapes of Iris germanica. Flower scapes were harvested with the oldest bud at ‘1 day before anthesis stage’, brought to laboratory under water, cut to a uniform length of 35 cm, divided into three sets viz., kinetin (KIN), 6-benzyl aminopurine (BAP) and thidiazuron (TDZ). Each set of scapes was treated with a particular cytokinin alone or in combination with 0.1 M sucrose. TDZ was effective than KIN and BAP in improving the postharvest life of the I. germanica scapes by 5.4 days as compared to the control (untreated scapes held in distilled water). This was because of the minimum percentage of bud abortion by TDZ application. Cytokinin application resulted in increased antioxidant activity, higher protein and phenolic content, besides a decrease in specific protease activity and α-amino acids in the tepal tissues. Application of TDZ resulted in the maximum increase in the superoxide dismutase, catalase and ascorbate peroxidase activity in the tepal tissues. The scapes treated with BAP and KIN maintained higher carbohydrate content in the tissue samples as compared to control and TDZ treated scapes. TDZ and BAP application resulted in increased membrane stability because of the decreased lipoxygenase activity which prevented membrane lipid peroxidation. Among the cytokinins tested, TDZ proved to be the promising cytokinin in improving the postharvest performance of beautiful flowers of I. germanica scapes.     

Biocontrol of Fusarium Root Rot in the Common Bean (Phaseolus vulgaris L.) by using Symbiotic Glomus mosseae and Rhizobium leguminosarum

Abstract The interaction between VA mycorrhiza Glomus mosseae (Gm), root rodulating symbiont Rhizobium leguminosarum (Rl), and root rot pathogen Fusarium solani (Fs) on the common bean (Phaseolus vulgaris) in relation to plant growth, nutrient uptake, disease severity, rhizosphere microbial biomass, and nutrient availability was investigated. Mycorrhizal plants yielded significantly greater plant biomass and mobilized more N and P uptake as compared to nonmycorrhizal plants or those infected with Fs. However, the mycorrhizal root colonizing ability, in presence of Fs, was reduced by 27%, whereas Rl enhanced it by 37%. The inoculation of Gm, besides decreasing propagule number of Fs in the rhizosphere, decreased pathogenic root rot by 34 to 77%. However, in the presence of Rl, Gm-inoculated plants were more tolerant of the fungal root pathogen. The Gm + Rl inoculated plants not only had maximum plant biomass and root nodulation, but also exhibited higher microbial biomass, alkaline phosphatase activity, and available phosphorus in their rhizosphere. Rl, alone or in association with Gm, caused the maximum increase in mineral nitrogen (NH₄ ⁺ and NO₃ ⁻) content in soil. These results indicate that Gm has a vital role in inhibiting the root pathogen from invasion, more so in the presence of R. leguminosarum. Received: 26 February 1996; Revised: 12 July 1996