Reversible binding of zinc in Plasmodium falciparum Sir2: Structure and activity of the apoenzyme

Reversible zinc chelation via thiol groups of cysteines leading to modulation of activity in redox regulated proteins forms a basis for switching on–off of various biochemical processes. Silent information regulator 2 (Sir2), a NAD⁺ dependent deacetylase, contains a non-catalytic zinc ion coordinated by thiol groups of cysteines. Using Plasmodium falciparum Sir2 (PfSir2), we have examined the effect of zinc removal on the structure and activity of this enzyme. Our studies show that the enzyme with high affinity for zinc exhibits partial collapse of structure upon removal of the metal ion. Zinc reconstitution of apo PfSir2 led to recovery of both structure and activity highlighting the reversibility of the process.     

Indirect regeneration of Withania somnifera and comparative analysis of withanolides in in vitro and greenhouse grown plants

The present study reports an efficient protocol for indirect shoot organogenesis and plantlets regeneration of Withania somnifera (L.) Dunal. Leaf explants were cultured on Murashige and Skoog (MS) medium supplemented with different concentrations and combinations of 6-benzylaminopurine (BAP) and indole-3-acetic acid (IAA). The highest callus induction rate (89.5 %) and shoot regeneration rate (92 %) were obtained when 2 mg dm⁻³ BAP was combined with 0.5 mg dm⁻³ IAA. Three major withanolides (withaferine A, 12-deoxywithastramonolide and withanolide A) were investigated in different plant organs from in vitro and greenhouse grown plants. Leaves contained higher contents of withanolides and phenolics than roots or stems, whereas roots contained the highest contents of flavonoids and polysacharides. In vitro grown plants contained greater contents of phenolics, flavonoids and polysaccharides while lower contents of withanolides than greenhouse grown plants.     

Application of RAPD markers for characterization of γ-ray-induced rose mutants and assessment of genetic diversity

Six parent and their 12 gamma ray-induced somatic flower colour mutants of garden rose were characterized to discriminate the mutants from their respective parents and understanding the genetic diversity using Random amplification of polymorphic DNA (RAPD) markers. Out of 20 primers screened, 14 primers yielded completely identical fragments patterns. The other 7 primers gave highly polymorphic banding patterns among the radiomutants. All the cultivars were identified by using only 7 primers. Moreover, individual mutants were also distinguished by unique RAPD marker bands. Based on the presence or absence of the 48 polymorphic bands, the genetic variations within and among the 18 cultivars were measured. Genetic distance between all 18 cultivars varied from 0.40 to 0.91, as revealed by Jaccard’s coefficient matrix. A dendrogram was constructed based on the similarity matrix using the Neighbor Joining Tree method showed three main clusters. The present RAPD analysis can be used not only for estimating genetic diversity present in gamma ray-induced mutants but also for correct identification of mutant/new varieties for their legal protection under plant variety rights.     

Arsenic affects mineral nutrients in grains of various Indian rice (Oryza sativa L.) genotypes grown on arsenic-contaminated soils of West Bengal

The exposure of paddy fields to arsenic (As) through groundwater irrigation is a serious concern that may not only lead to As accumulation to unacceptable levels but also interfere with mineral nutrients in rice grains. In the present field study, profiling of the mineral nutrients (iron (Fe), phosphorous, zinc, and selenium (Se)) was done in various rice genotypes with respect to As accumulation. A significant genotypic variation was observed in elemental retention on root Fe plaque and their accumulation in various plant parts including grains, specific As uptake (29–167 mg kg^?1 dw), as well as As transfer factor (4–45%). Grains retained the least level of As (0.7–3%) with inorganic As species being the dominant forms, while organic As species, viz., dimethylarsinic acid and monomethylarsonic acid, were non-detectable. In all tested varieties, the level of Se was low (0.05–0.12 mg kg^?1 dw), whereas that of As was high (0.4–1.68 mg kg^?1 dw), considering their safe/recommended daily intake limits, which may not warrant their human consumption. Hence, their utilization may increase the risk of arsenicosis, when grown in As-contaminated areas.     

Synthesis and QSAR studies on hypotensive 1-[3-(4-substituted phenylthio) propyl]-4-(substituted phenyl) piperazines

A series of 1-[3-(4-substituted phenylthio) propyl]-4-(substituted phenyl) piperazines has been synthesized and evaluated for hypotensive activity. The QSAR studies indicate that resonance and hydrophobic parameters of the aryl substituents are important for hypotensive activity. The similar role of resonance parameter in describing the variance of 5-HT(2A) receptor binding affinities of these compounds suggests a possible role of 5-HT(2A) receptors in mediating the hypotensive action of title compounds.     

Beyond host-pathogen interactions: microbial defense strategy in the host environment

Many extracellular pathogenic bacteria colonize human or animal bodies through evasion of the host immune system, a process called host-pathogen interaction. What happens when other intruders try to invade the same host and try to establish themselves in the same niche is largely unknown. In one well-studied case, Pseudomonas aeruginosa is known to secrete the protein azurin as a weapon against such invaders as cancers, parasites and viruses. The production of such weapons by pathogenic bacteria could provide important insights into how a pathogen responds in the post-colonization state to impede other intruders for its own survival. Moreover, these molecules might find use in the pharmaceutical industry as next-generation therapeutics.     

Effects of Hydroponic Solution EC,Substrates, PPF and Nutrient Scheduling on Growth and Photosynthetic Competence During Acclimatization of Micropropagated <Emphasis Type="Italic">Spathiphyllum</Emphasis> plantlets

In vitro regenerated shoots of Spathiphyllum from bioreactor were hydroponically cultured for 30 days. The response of plant growth and photosynthesis to different substrates, photosynthetic photon flux (PPF), nutrient scheduling and electrical conductivity (EC) of hydroponic solution were studied. The best plant growth response was observed in perlite based substrates with moderate PFF (70–100μmol m⁻² s⁻¹). Highest fresh weight, dry weight, shoot length, root length, root number and photosynthetic characteristics (chlorophyll, carotenoids and Fv/Fm) was observed in continuous immersion system. Plant growth responses, photosynthetic rate, stomatal conductance and transpiration rate were also found to be affected by EC levels. The optimum EC of a balanced nutrient solution was recorded as 1.2 dS m⁻¹. Photosynthetic activity was also characterized in terms of photochemical efficiency using measurements of chlorophyll fluorescence. Fv/Fm (it is a measure of the intrinsic or maximum efficiency of PSII i.e. the quantum efficiency if all PSII centers were open) also decreased significantly in plants grown under higher EC level; a decrease in this parameter indicates down regulation of photosynthesis or photoinhibition. Antioxidant defense enzymes such as catalase (CAT), ascorbate peroxidase (APX), peroxidase (POD), glutathione reductase (GR) and monodehydroascorbate reductase (MDHAR) significantly elevated in the leaves and roots of plantlets at higher EC levels. This increase could reflect a defense response to the cellular damage provoked by higher EC levels in the nutrient solution.     

Sufficient progesterone-priming prior to estradiol stimulation is required for optimal induction of the cervical prostaglandin system in pregnant sheep at 0.7 gestations

The purposes of this study were to determine the separate and interactive functions of progesterone and estradiol in regulating the cervical prostaglandin (PG) system in pregnant sheep at 0.7 gestations. At 106-108 days of gestational age (dGA), ewes were treated with vehicle for 14 days (n = 5) or vehicle for 12 days followed by estradiol 5 mg twice a day, intramuscularly for 2 days (n = 5) or progesterone 100 mg, twice a day, intramuscularly for 14 days (n = 5) or progesterone 100 mg twice a day, intramuscularly for 10 days and then 2 days vehicle followed by estradiol 5 mg twice a day intramuscularly for 2 days (n = 5). At 121-123 dGA, cervical tissues were obtained under halothane anesthesia. Cervical RNA and protein were extracted and analyzed for prostaglandin-endoperoxide synthase 2 (COX2), two PGE(2) receptors, PTGER2 and PTGER4, and estrogen receptor alpha (ESR1) by Northern and Western blot analysis. Immunocytochemistry and in situ hybridization were applied to localize cellular distribution of COX2, PTGER2, and PTGER4 in the cervix. Data were analyzed by ANOVA. COX2 and PTGER4 mRNAs and proteins were increased (P < 0.05) in ewes treated with combined estradiol and progesterone but not in ewes treated with estradiol or progesterone alone compared with controls. ESR1 mRNA was increased in ewes treated with progesterone and estradiol plus progesterone. In contrast, PTGER2 mRNA and protein remained the same after all treatments. COX2 mRNA and protein were localized only in cervical glandular epithelial cells, whereas PTGER2 and PTGER4 were localized in both cervical glandular epithelial and smooth muscle cells. In conclusion, these data suggest that additional progesterone priming at 0.7 gestations synergizes with estradiol to induce cervical COX2, PTGER4, and ESR1 and support our hypothesis that stimulation of the cervical PG system by estradiol is optimized by sufficient progesterone priming in the pregnant sheep cervix.