Down-regulation of lignin biosynthesis in transgenic Leucaena leucocephala harboring O-methyltransferase gene

In the present study, a 0.47 kb OMT gene construct from aspen, encoding for an enzyme O-methyltransferase (OMT, EC 2.1.1.6), in antisense orientation was used to down-regulate lignin biosynthesis in Leucaena leucocephala. The plants were transformed with Agrobacterium tumefaciens strain harboring the antisense gene, and the transformation was confirmed by PCR amplification of the npt II gene. The integration of a heterologous antisense OMT gene construct in transformed plants led to a maximum of 60% reduction in OMT activity relative to control. The evaluation of total lignin content by the Klason method revealed a maximum of 28% reduction. Histochemical analyses of stem sections depicted a reduction in lignin content and normal xylem development. The results also suggested a probable increase in aldehyde levels and a decrease in syringyl units. Lignin down-regulation was accompanied by an increase in methanol soluble phenolics to an extent that had no impact on wood discoloration, and the plants displayed a normal phenotype. Concomitantly, an increase of up to 9% in cellulose content was also observed. Upon alkali extraction, modified lignin was more extractable as evident from reduced Klason lignin in saponified residue and increased alkali soluble phenolics. The results together suggested that the extent of down-regulation of OMT activity achieved may lead to quality amelioration of Leucaena with respect to its applicability in pulp and paper manufacture as well as nutritive and easily digestible forage production.     

A distal axonal cytoskeleton forms an intra-axonal boundary that controls axon initial segment assembly

AnkyrinG (ankG) is highly enriched in neurons at axon initial segments (AISs) where it clusters Na(+) and K(+) channels and maintains neuronal polarity. How ankG becomes concentrated at the AIS is unknown. Here, we show that as neurons break symmetry, they assemble a distal axonal submembranous cytoskeleton, comprised of ankyrinB (ankB), αII-spectrin, and βII-spectrin, that defines a boundary limiting ankG to the proximal axon. Experimentally moving this boundary altered the length of ankG staining in the proximal axon, whereas disruption of the boundary through silencing of ankB, αII-spectrin, or βII-spectrin expression blocked AIS assembly and permitted ankG to redistribute throughout the distal axon. In support of an essential role for the distal cytoskeleton in ankG clustering, we also found that αII and βII-spectrin-deficient mice had disrupted AIS. Thus, the distal axonal cytoskeleton functions as an intra-axonal boundary restricting ankG to the AIS.     

Biodegradation kinetics of methyl iso-butyl ketone by acclimated mixed culture

Methyl iso-butyl ketone (MIBK) is a widely used volatile organic compound (VOC) which is highly toxic in nature and has significant adverse effects on human beings. The present study deals with the removal of MIBK using biodegradation by an acclimated mixed culture developed from activated sludge. The biodegradation of MIBK is studied for an initial MIBK concentration ranging from 200–700 mg l⁻¹ in a batch mode of operation. The maximum specific growth rate achieved is 0.128 h⁻¹ at 600 mg l⁻¹of initial MIBK concentration. The kinetic parameters are estimated using five growth kinetic models for biodegradation of organic compounds available in the literature. The experimental data found to fit well with the Luong model (R ² = 0.904) as compared to Haldane model (R ² = 0.702) and Edward model (R ² = 0.786). The coefficient of determination (R ²) obtained for the other two models, Monod and Powell models are 0.497 and 0.533, respectively. The biodegradation rate found to follow the three-half-order kinetics and the resulting kinetic parameters are reported.     

Molecular Detection and Exploration of Diversity Among Fungal Consortium Involved in Phosphate Solubilization

Abstract

Phosphorous (P) that upholds life become unattainable as most of them become unavailable due to the formation of insoluble complexes with cations such as Ca²⁺, Al³⁺ and Fe³⁺ forming a complex calcium phosphate (Ca₃(PO₄)₂), aluminum phosphate (AlPO) and ferrous phosphate (FePO) that results in the decrease of soluble P to a greater extent. There are several reports stating that several rhizospheric fungal species play an important role in solubilizing these insoluble phosphates into a soluble form by the excretion of enzymes like phosphatase, phytase enzymes, and organic acids. In view of this, so we have collected twenty fungal isolates having probable phosphate solubilizing efficiency from different regions of Lucknow, India. Their morphological and biochemical characteristics were tested. Among all, six efficient fungal isolates were further checked at molecular level by using 18S rRNA universal primers and by RAPD means. A dendrogram indicated 40-90% homology i.e., highest similarity was found in between species of Aspergillus flavus and A. biplanus with 33.8% similarity while minimum similarity was observed among A. flavus and Fusarium oxysporum. These findings suggest RAPD proves as, a reliable molecular tool that helps in strain specific discrimination.     

Methane flux from rice/wheat agroecosystem as affected by crop phenology, fertilization and water level

Methane flux was measured for a rice/wheat agroecosystem of Gangetic Plains, with and without application of chemical fertilizer and wheat straw (WS). Three treatments of control, fertilizer application and fertilizer + WS application, were established in a completely randomized block design and measurements were made for two consecutive years (1993 and 1994). CH₄ measurements during growth of the rice crop period showed that there were significant difference in flux rates during the two years. Maximum emission occurred at the time of anthesis and minimum at the seedling stage. The flux rates were significantly higher for fertilizer or fertilizer + WS treatments. The effects of the treatments were similar across phenological stages and years. In the subsequent wheat crop and fallow period, the soils consumed CH₄. There were significant differences in CH₄ uptake rates between the two years. Fertilizer treatments reduced CH₄ uptake in both the years. The results suggested that tropical agroecosystems may consume substantial amounts of CH₄ and that the methane output can be reduced by lowering the submergence level in rice paddies.     

Helicobacter pylori picB, a homologue of the Bordetella pertussis toxin secretion protein, is required for induction of IL-8 in gastric epithelial cells

Approximately 60% of Helicobacter pylori strains are cagA ⁺ and this genotype is more frequently associated with duodenal ulcer disease. Although most wild-type cagA ⁺ strains are both cytotoxigenic and induce enhanced Interleukin-8 (IL-8) secretion in gastric epithelial cells, isogenic cagA ⁻ mutants retain full activity in these assays; thus, cagA appears to be a marker of enhanced virulence. Delineation of the nucleotide sequence of a 4 kb region upstream of cagA allowed the identification of 966 bp ( picA ) and 2655 bp ( picB ) open reading frames encoding 36 kDa and 101 kDa polypeptides, respectively. picA and picB constitute an operon in opposite orientation to cagA . The deduced picB product showed significant homology (26% identity and 50% similarity) with the Bordetella pertussis toxin secretion protein (PtlC). Of 55 H. pylori clinical isolates, the picA and picB segment was conserved exclusively in cagA ⁺ strains and present in all isolates from patients with duodenal ulceration, versus 59% of isolates from patients with gastritis alone ( P =0.01). Using gene-replacement techniques, we constructed picA and picB mutant H. pylori strains and demonstrated that the picB gene product is involved in the induction of IL-8 expression in gastric epithelial cells. Further, Northern blot hybridization and RT-PCR data showed that picA and picB are co-transcribed and an insertional mutation in picA ablates picB expression. These studies indicate a role of picA and picB in the induction of an inflammatory response in gastric epithelial cells either directly or by enabling secretion of an unidentified product, and suggest a mechanism for the overrepresentation of strains possessing these genes in patients with peptic ulceration.     

Characterization of antibodies to chicken riboflavin carrier protein: Antigenicity of the tryptic fragments

The antigenecity of tryptic fragments of reduced and carboxymethylated chicken riboflavin carrier protein were studied. The tryptic sites of the native riboflavin carrier protein bound to riboflavin were inaccessible. The molecular weight and the elution profile on high performance liquid chromatography (TSK 545 DEAE) were unaltered at an enzyme to substrate ratio of 1:31. However, carboxymethylated riboflavin carrier protein could be cleaved into 3 or 4 fragments at an enzyme to substrate ratio of 1:250 or 1:125. Chromatographic separation of the tryptic fragments on high pressure liquid chromatography (TSK 545 DEAE) revealed the presence of two fragments with different elution profiles but similar molecular weight 26 ±2 kDa. Only one fragment (associated with peak 2) had the ability to displace chicken riboflavin carrier protein in an homologous chicken riboflavin carrier protein radioimmunoassay. Thus, carboxymethylated ribotlavin carrier protein which does not compete with chicken riboflavin carrier protein in the radioimmunoassay, on mild trypsinization generates a fragment which interacts with chicken riboflavin carrier protein in radioimmunoassay.