Low host specificity of root‐associated fungi at an Arctic site

In High Arctic ecosystems, plant growth and reproduction are limited by low soil moisture and nutrient availability, low soil and air temperatures, and a short growing season. Mycorrhizal associations facilitate plant nutrient acquisition and water uptake and may therefore be particularly ecologically important in nutrition‐poor and dry environments, such as parts of the Arctic. Similarly, endophytic root associates are thought to play a protective role, increasing plants' stress tolerance, and likely have an important ecosystem function. Despite the importance of these root‐associated fungi, little is known about their host specificity in the Arctic. We investigated the host specificity of root‐associated fungi in the common, widely distributed arctic plant species Bistorta vivipara, Salix polaris and Dryas octopetala in the High Arctic archipelago Svalbard. High‐throughput sequencing of the internal transcribed spacer 1 (ITS1) amplified from whole root systems generated no evidence of host specificity and no spatial autocorrelation within two 3 m × 3 m sample plots. The lack of spatial structure at small spatial scales indicates that Common Mycelial Networks (CMNs) are rare in marginal arctic environments. Moreover, no significant differences in fungal OTU richness were observed across the three plant species, although their root system characteristics (size, biomass) differed considerably. Reasons for lack of host specificity could be that association with generalist fungi may allow arctic plants to more rapidly and easily colonize newly available habitats, and it may be favourable to establish symbiotic relationships with fungi possessing different physiological attributes.     

Effect of acute and chronic cholinesterase inhibition on biogenic amines in rat brain

The effects of five cholinesterase inhibitors on forebrain monoamine and their metabolite levels, and on forebrain and plasma cholinesterase (ChE) activity in rat were studied in acute and chronic conditions. Acute tetrahydroaminoacridine (THA) dosing caused lower brain (68%) and higher plasma (90%) ChE inhibition than the other drugs studied increased levels of brain dihydroxyphenylacetic acid (DOPAC) (236%), homovanillic acid (HVA) (197%) and 5-hydroxyindolaecetic acid (5-HIAA) (130%). Acute physostigmine (PHY) administration caused a 215% increase in brain DOPAC content. Despite high brain ChE inhibition induced by metrifonate (MTF), dichlorvos (DDVP) or naled no changes in brain noradrenaline (NA), dopamine (DA) or serotonin (5-HT) occurred due to treatment with the study drugs in the acute study. In the chronic 10-day study THA or PHY caused no substantial ChE inhibition in brain when measured 18 hours after the last dose, whereas MTF induced 74% ChE inhibition. Long-term treatment with THA or MTF caused no changes in monoamine levels, but PHY treatment resulted in slightly increased 5-HT values. These results suggest that MTF, DDVP and naled seem to act solely by cholinergic mechanisms. However, the central neuropharmacological mechanism of action of THA and PHY may involve changes in cholinergic as well as dopaminergic and serotoninergic systems.     

Fluorescence resonance energy transfer from tryptophan to a chromium(III) complex accompanied by non-specific cleavage of albumin: a step forward towards the development of a novel photoprotease

A chromium(III) complex, transdiaqua [N, N'-propylenebis(salicylideneimino)chromium(III)]perchlorate ([Cr(salprn)(H2O)(2)]ClO(4)) in the presence of sodium azide and upon photoexcitation was found to bring about non-selective cleavage of bovine serum albumin (BSA). Electron paramagnetic resonance (EPR) evidence has been obtained for the formation of a Cr(V) species upon photolysis of a solution containing the chromium(III) complex and sodium azide. This Cr(V) species non-selectively cleaves BSA. The fluorescence excitation spectrum of BSA-[Cr(salprn)(H2O)(2)]+ adduct showed a band at lambda(max)(ex) nm due to charge transfer transition of the chromium(III) complex as well as a prominent band at 290 nm attributable to tryptophan absorption. This indicated an efficient Forster type fluorescence energy transfer (FRET) from the tryptophan residues to the chromium(III) complex indicating that the Cr(III) complex binds in the vicinity of the tryptophan residue.     

Interaction of aldehydes with collagen: effect on thermal, enzymatic and conformational stability

Stabilization of type I rat tail tendon (RTT) collagen by various aldehydes, viz. formaldehyde, gluteraldehyde, glyoxal and crotanaldehyde was studied to understand the effect of each on the thermal, enzymatic and conformational stability of collagen. The aldehydes have been found to increase the heat stability of rat tail tendon collagen fibres from 62 to 77-86 degrees C. The increase in thermal stability was found to be in a species dependent manner. The variation in the thermal stability of collagen brought about by aldehydes was in the order of formaldehyde > gluteraldehyde > glyoxal > crotanaldehdye. The aldehydes also impart a high degree of stability to collagen against the activity of the degrading enzyme, collagenase. The order of enzymatic stability brought about by aldehydes follows the same trend as the thermal stability brought about by them. This shows that the number of cross-links formed influence both the thermal and enzymatic stability in the similar manner. The effect of various aldehydes on the secondary structure of collagen was studied using circular dichroism and it was found that the aldehydes lead to changes in the amplitude of the circular dichroic (CD) spectrum but did not alter the triple helical conformation of collagen. The secondary structure of collagen is not significantly altered on interaction with different aldehydes.     

Production and partial purification of cellulase from a novel fungus,Aspergillus flavus BS1

This study describes the isolation and characterization of a novel fungus, Aspergillus flavus BS1 and its cellulolytic activities with special emphasis on endoglucanase production. Preliminary screening studies showed that A. flavus BS1 was a potent strain for the production of cellulase. To study the cellulolytic activities in detail by submerged fermentation (SmF), productions of endoglucanase, exoglucanase, and β-glucosidase were estimated from the basal salt medium (BSM) supplemented with 1 % carboxy methyl cellulose (CMC). CMC medium supported the maximum yield of endoglucanase (2,793 U/ml) on day 5 of incubation at 28 °C and 150 rpm, which was higher than that obtained with naturally available supplements (flour) from banana, tapioca, potato, or banana peel. During cellulase production by solid-state fermentation, 10 % (w/w) tapioca flour in sawdust (teak wood) moisturized with BSM (1:2, w/v) supported maximum cellulase yield (5,408 U/g dry substrate) on day 3 at 28 °C, which was 2-fold higher than that obtained during SmF. The active cellulase was qualitatively estimated by polyacrylamide gel electrophoresis (PAGE). Native-PAGE (0.25 % CMC impregnated on the 10 % gel) activity staining with congo-red showed a clear zone for CMCase activity, whereas SDS-PAGE showed a distinct band. In conclusion, this study showed that A. flavus strain BS1 is a potent strain for the production of cellulase on lignocellulosic media, the hot enzyme for bioethanol production from the lignocellulosic biomass by SSF.     

C-terminal phosphorylation of murine testis-specific histone H1t in elongating spermatids

Previous studies gave differing results as to whether the testis-specific histone H1t was phosphorylated during rodent spermatogenesis. We show here that histones extracted from germ cell populations enriched with spermatids at different stages of development in rat testes reveal an electrophoretic shift in the position of H1t to slower mobilities in elongating spermatids as compared to that from preceding stages. Alkaline phosphatase treatment and radioactive labeling with (32)P demonstrated that the electrophoretic shift is due to phosphorylation. Mass spectrometric analysis of histone H1t purified from sexually mature mice and rat testes confirmed the occurrence of singly, doubly, and triply phosphorylated species, with phosphorylation sites predominantly found at the C-terminal end of the molecule. Furthermore, using collision-activated dissociation (CAD) and electron transfer dissociation (ETD), we have been able to identify the major phosphorylation sites. These include a new, previously unidentified putative H1t-specific cdc2 phosphorylation site in linker histones. The presence of phosphorylation at the C-terminal end of H1t and the timing of its appearance suggest that this post-translational modification is involved in the reduction of H1t binding strength to DNA. It is proposed that this could participate in the opening of the chromatin fiber in preparation for histone displacement by transition proteins in the next phase of spermiogenesis.     

Interaction of chromium(III) complex of chiral binaphthyl tetradentate ligand with DNA

Since conformation of the molecule plays a vital role in the activity of drug, we have investigated the DNA interaction of a chromium(III) complex with ligands in two conformations. Chromium(III) complexes derived from chiral binaphthyl Schiff base ligands, viz. R- and S-2,2'-bis(salicylideneamino) 1,1'-binaphthyl, have been synthesized and characterized by mass, IR, and electronic spectra. The interaction of these R- and S-binaphthyl Schiff base chromium(III) complexes with CT-DNA was investigated with the goal of examining whether the chirality has an influence on the chromium(III)-DNA binding properties. The difference in chirality of the ligand did not show any striking difference in binding properties. The binding constants for R and S conformers were estimated to be 18 (+/-0.4) x 10(3) and 9.4 (+/-0.3) x 10(3) M(-1), respectively, through spectroscopic titrations. All the experimental results are suggestive that both the isomers are DNA groove binders. The results of steady-state as well as time-resolved fluorescence experiments, however, suggest that the R conformer has restricted mobility when bound to DNA because it is more deeply buried in the groove of DNA compared to the S isomer.