Amino acid substitution in α-helix 7 of Cry1Ac δ-endotoxin of Bacillus thuringiensis leads to enhanced toxicity to Helicoverpa armigera Hubner

AbstractInsecticidal proteins or δ-endotoxins of Bacillus thuringiensis are highly toxic to a wide range of agronomically important pests. The toxins are formed of three structural domains. The N-terminal domain is a bundle of eight α-helices and is implicated in pore formation in insect midgut epithelial membranes. All the δ-endotoxins share a common hydrophobic motif of eight amino acids in α-helix 7. A similar motif is also present in fragment B of diphtheria toxin (DT). Site-directed mutagenesis of Cry1Ac δ-endotoxin of B. thuringiensis was carried out to substitute its hydrophobic motif with that of DT fragment B. The mutant toxin was shown to be more toxic to the larvae of Helicoverpa armigera (cotton bollworm) than the wild-type toxin. Voltage clamp analysis with planar lipid bilayers revealed that the mutant toxin opens larger ion channels and induces higher levels of conductance than the wild-type toxin

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Not AvailableImpact of osmoregulation on plasma sex steroid levels and gonadal histo-architecture was monitored to elucidate the effects of deviation from habitat salinity on gonadal recrudescence in an active reproductive season of an euryhaline fish Etroplus suratensis (pearlspot). Fish were maintained in three different salinities of 0 ppt Fresh Water (FW), 15 ppt Brackish Water (BW) and 30 ppt Sea Water (SW) for a period of 60 days. Plasma osmolality values were found to be significantly highest in SW-acclimated fish accompanied by highest levels of plasma K⁺ and Cl¯ ions. The progress of gonadal recrudescence was higher in BW followed by FW and SW as evident from the cellular features of gonads and increased level of plasma sex steroids, such as, in case of female and 11-keto Testosterone and Testosterone in case of males. Plasma cortisol levels were comparatively higher in fish of both sexes in SW group. Significantly high levels of cortisol in SW suggest its role in hypo-osmoregulation and associated stress. This study clearly reveals that salinity changes during the active reproductive phase can suppress the steroid-mediated gonad recrudescence maximally under hypo-osmoregulation in an euryhaline fish.Not Availabl

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Not AvailableDiel cyclic hypoxia occurs with varying frequency and duration in freshwater habitats, yet little is known about its effects on reproduction of freshwater fishes. The present study shows that long-term exposure of goldfish (Carassius auratus) to cyclic hypoxia (0.8 ± 0.2 mg/l dissolved oxygen) for 9 h or more, per day, altered plasma lipid and sex steroid profiles, which in turn directly or indirectly suppressed ovarian growth and viable spermatozoa production. Hypoxia decreased total cholesterol and high density lipoprotein (HDL p < 0.05) and elevated triglycerides (TG; p < 0.05) in both sexes. Plasma steroid concentrations particularly of 17α-hydroxyprogesterone (17-HP), estradiol (E2), testosterone (T) in females, and T and 11-ketotestosterone (11-KT) in males were attenuated under diel hypoxic conditions. Intriguingly, both diel and continuous hypoxia elevated plasma E2 and vitellogenin levels in males. However, neither lipid nor steroid profiles recorded any variation in a dose-dependent manner in response to diel hypoxia. The reduced GSI, decreased number of tertiary oocytes, and motile spermatozoa in hypoxic fish clearly indicate suppression of gametogenesis. Thereby, prolonged diel cyclic hypoxia may affect valuable fishery resources and fish population structure by impairing reproductive performances and inducing estrogenic effects in males.Not Availabl

p53 dependent apoptotic cell death induces embryonic malformation in Carassius auratus under chronic hypoxia.

Hypoxia is a global phenomenon affecting recruitment as well as the embryonic development of aquatic fauna. The present study depicts hypoxia induced disruption of the intrinsic pathway of programmed cell death (PCD), leading to embryonic malformation in the goldfish, Carrasius auratus. Constant hypoxia induced the early expression of pro-apoptotic/tumor suppressor p53 and concomitant expression of the cell death molecule, caspase-3, leading to high level of DNA damage and cell death in hypoxic embryos, as compared to normoxic ones. As a result, the former showed delayed 4 and 64 celled stages and a delay in appearance of epiboly stage. Expression of p53 efficiently switched off expression of the anti-apoptotic Bcl-2 during the initial 12 hours post fertilization (hpf) and caused embryonic cell death. However, after 12 hours, simultaneous downregulation of p53 and Caspase-3 and exponential increase of Bcl-2, caused uncontrolled cell proliferation and prevented essential programmed cell death (PCD), ultimately resulting in significant (p<0.05) embryonic malformation up to 144 hpf. Evidences suggest that uncontrolled cell proliferation after 12 hpf may have been due to downregulation of p53 abundance, which in turn has an influence on upregulation of anti-apoptotic Bcl-2. Therefore, we have been able to show for the first time and propose that hypoxia induced downregulation of p53 beyond 12 hpf, disrupts PCD and leads to failure in normal differentiation, causing malformation in gold fish embryos

Inter-specific variation in headspace scent volatiles composition of four commercially cultivated jasmine flowers

<div><p>Jasmines are commercially grown for their fragrant flowers and essential oil production. The flowers of jasmine emit sweet-smelling fragrance from evening till midnight. This study was designed to study the composition and inter-specific variation of the emitted scent volatiles from flowers of four commercially cultivated <i>Jasminum</i> species namely, <i>Jasminum sambac</i>, <i>Jasminum auriculatum, Jasminum grandiflorum</i> and <i>Jasminum multiflorum</i>. Gas chromatography-mass spectrometry analysis revealed that the scent volatiles composition of these flowers was predominantly enriched with both terpenoid and benzenoid compounds. Linalool and (3<i>E</i>,6<i>E</i>)-α-farnesene were identified as the major monoterpene and sesquiterpene in all the four species, respectively. The most abundant benzenoid detected in all flowers was benzyl acetate. Comparison of volatile profiles indicated a variation in fragrance contents and types emitted from these four jasmine flowers. The outcome of this study shall help in elucidating the enzymes and genes of fragrance biosynthesis in jasmines and in aiming to create flowers with improved scent quality.</p></div

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Biostimulation of indigenous microbial community for bioremediation of petroleum refinery sludge.

Nutrient deficiency severely impairs the catabolic activity of indigenous microorganisms in hydrocarbon rich environments (HREs) and limits the rate of intrinsic bioremediation. The present study aimed to characterize the microbial community in refinery waste and evaluate the scope for biostimulation based in situ bioremediation. Samples recovered from the wastewater lagoon of Guwahati refinery revealed a hydrocarbon enriched high total petroleum hydrocarbon (TPH), oxygen-, moisture-limited, reducing environment. Intrinsic biodegradation ability of the indigenous microorganisms was enhanced significantly (>80% reduction in TPH by 90 days) with nitrate amendment. Preferred utilization of both higher- (>C30) and middle- chain (C20-30) length hydrocarbons were evident from GC-MS analysis. Denaturing gradient gel electrophoresis (DGGE) and community level physiological profiling (CLPP) analyses indicated distinct shift in community’s composition and metabolic abilities following nitrogen (N) amendment. High throughput deep sequencing of 16S rRNA gene showed that the native community was mainly composed of hydrocarbon degrading, syntrophic, methanogenic, nitrate/iron/sulfur reducing facultative anaerobic bacteria and archaebacteria, affiliated to γ- and δ-Proteobacteria and Euryarchaeota respectively. Genes for aerobic and anaerobic alkane metabolism (alkB and bssA), methanogenesis (mcrA), denitrification (nirS and narG) and N2 fixation (nifH) were detected. Concomitant to hydrocarbon degradation, lowering of dissolve O2 and increase in oxidation-reduction potential (ORP) marked with an enrichment of N2 fixing, nitrate reducing aerobic/facultative anaerobic members e.g., Azovibrio, Pseudoxanthomonas and Commamonadaceae members was evident in N amended microcosm. This study highlighted that indigenous community of refinery sludge was intrinsically diverse, yet appreciable rate of in situ bioremediation could be achieved by supplying adequate N sources

Developmental variation in floral volatiles composition of a fragrant orchid <i>Zygopetalum maculatum</i> (Kunth) Garay

<p>Emitted scent volatile profile of an orchid species <i>Zygopetalum maculatum</i> was studied using dynamic headspace sampling technique with four different adsorbent matrices, namely Porapak Type Q polymer (mesh size: 80/100), Tenax (mesh size: 60/80), activated charcoal and graphite. In addition, developmental variations in scent emissions and endogenous volatile levels were also investigated. Gas chromatography-mass spectrometry analysis revealed the presence of 21 volatile compounds in the headspace, which was predominantly enriched with benzenoid compounds. Among these benzenoids, <i>o</i>-diethylbenzene and <i>p</i>-diethylbenzene were the major compounds followed by benzyl acetate and methyl salicylate. Among the phenylpropanoid compounds, 2-phenylethyl acetate was the major volatile. However, as compared to benzenoids, the quantity was much lesser, indicating the inclination of phenylalanine flux towards benzenoid pathway. The outcome of this study has the implications in enhancing fragrance and vase life of orchids of the Sikkim Himalaya region and thus may further help to meet the growing market demand.</p

Characterization of pattern of cell death and cellular DNA fragmentation.

<p>(A). Type of cell death (Apoptotic or Necrotic): DNA fragments in hypoxic cell lysate significantly increased (<i>p</i><0.05) after 1 h of incubation and reached highest level at 3 h and continued to be high up to 9 h, with a small peak at 6 h. No BrdU labeled DNA fragment was detected in the hypoxic cell supernatants during first 4 hours of incubation, indicating that DNA fragmentation had occurred prior to lysis of plasma membrane; Hence, cause of cell death may be attributed to apoptosis and not due to necrosis, under hypoxia. (B). DNA fragmentation: Phenomena of cellular DNA fragmentation under hypoxia started increasing after blastula (4 hpf) stage and reached its highest (<i>p</i><0.05) during gastrula phase (7 hpf), thereafter returning to the level of control after 12 h. Different superscripts indicate significant differences (p<0.05) amongst normoxic and hypoxic groups at different times. Values are expressed as mean ± SEM (n = 10).</p