Seasonal variability in net ecosystem carbon dioxide exchange over a young Switchgrass stand

Understanding carbon dynamics of switchgrass ecosystems is crucial as switchgrass (Panicum virgatum L.) acreage is expanding for cellulosic biofuels. We used eddy covariance system and examined seasonal changes in net ecosystem CO₂ exchange (NEE) and its components – gross ecosystem photosynthesis (GEP) and ecosystem respiration (ER) – in response to controlling factors during the second (2011) and third (2012) years of stand establishment in the southern Great Plains of the United States (Chickasha, OK). Larger vapor pressure deficit (VPD > 3 kPa) limited photosynthesis and caused asymmetrical diurnal NEE cycles (substantially higher NEE in the morning hours than in the afternoon at equal light levels). Consequently, rectangular hyperbolic light–response curve (NEE partitioning algorithm) consistently failed to provide good fits at high VPD. Modified rectangular hyperbolic light–VPD response model accounted for the limitation of VPD on photosynthesis and improved the model performance significantly. The maximum monthly average NEE reached up to ?33.02 ± 1.96 μmol CO₂ m^?2 s^?1 and the highest daily integrated NEE was ?35.89 g CO₂ m^?2 during peak growth. Although large differences in cumulative seasonal GEP and ER were observed between two seasons, total seasonal ER accounted for about 75% of GEP regardless of the growing season lengths and differences in aboveground biomass production. It suggests that net ecosystem carbon uptake increases with increasing GEP. The ecosystem was a net sink of CO₂ during 5–6 months and total seasonal uptakes were ?1128 ± 130 and ?1796 ± 217 g CO₂ m^?2 in 2011 and 2012, respectively. In conclusion, our findings suggest that the annual carbon status of a switchgrass ecosystem can be a small sink to small source in this region if carbon loss from biomass harvesting is considered. However, year‐round measurements over several years are required to assess a long‐term source‐sink status of the ecosystem.     

IL-4 Haplotype -590T, -34T and Intron-3 VNTR R2 Is Associated with Reduced Malaria Risk among Ancestral Indian Tribal Populations

Background

Interleukin 4 (IL-4) is an anti-inflammatory cytokine, which regulates balance between T_H1 and T_H2 immune response, immunoglobulin class switching and humoral immunity. Polymorphisms in this gene have been reported to affect the risk of infectious and autoimmune diseases.

Methods

We have analyzed three regulatory IL-4 polymorphisms; -590C>T, -34C>T and 70 bp intron-3 VNTR, in 4216 individuals; including: (1) 430 ethnically matched case-control groups (173 severe malaria, 101 mild malaria and 156 asymptomatic); (2) 3452 individuals from 76 linguistically and geographically distinct endogamous populations of India, and (3) 334 individuals with different ancestry from outside India (84 Brazilian, 104 Syrian, and 146 Vietnamese).

Results

The -590T, -34T and intron-3 VNTR R2 alleles were found to be associated with reduced malaria risk (P<0.001 for -590C>T and -34C>T, and P = 0.003 for VNTR). These three alleles were in strong LD (r²>0.75) and the TTR2 (-590T, -34T and intron-3 VNTR R2) haplotype appeared to be a susceptibility factor for malaria (P = 0.009, OR = 0.552, 95% CI = 0.356 –0.854). Allele and genotype frequencies differ significantly between caste, nomadic, tribe and ancestral tribal populations (ATP). The distribution of protective haplotype TTR2 was found to be significant (χ² ₃ = 182.95, p-value <0.001), which is highest in ATP (40.5%); intermediate in tribes (33%); and lowest in caste (17.8%) and nomadic (21.6%).

Conclusions

Our study suggests that the IL-4 polymorphisms regulate host susceptibility to malaria and disease progression. TTR2 haplotype, which gives protection against malaria, is high among ATPs. Since they inhabited in isolation and mainly practice hunter-gatherer lifestyles and exposed to various parasites, IL-4 TTR2 haplotype might be under positive selection.     

Analysis of activity driven by upstream regulatory modules (URM) of tapetum specific genes TA29 and A9 at ectopic locations in tobacco transgenics

TA29 and A9 are genes from Nicotiana tabacum and Arabidopsis thaliana respectively, which express in a tapetum specific manner. The upstream regulatory modules (URMs; i.e. the promoter and the 5′UTR) of these genes have been used in development of male sterile and restorer lines expressing the barnase and barstar genes for hybrid seed production. While initial studies show that these URMs drive the expression in a tapetum specific manner, there are no recordings of unintended (leaky) expression driven by these URMs at ectopic locations due to position effect in developed transgenic lines. The information on leaky expression driven by tissue specific URMs is important for their use in developing transgenic plants. The present study records the leaky activity of both these URMs in transgenic tobacco lines using β-glucuronidase as a reporter gene. Leaky activity was observed in about one-fourth of the lines developed with TA29. Most interestingly in these lines, the leaky expression of the reporter gene was observed to be restricted to the meristematic tip region of the roots and at the leaf gap from where leaf trace diverges from stem bundles. Such a restricted and unique pattern of leaky activity of a tissue specific promoter or a URM has never been reported before, including the URM of the A9 gene analyzed in the present study. This observation suggests the presence of cryptic cis-elements within the URM of TA29 gene that can possibly activate it in meristematic tissue when integrated at certain ectopic locations. The URM of the A9 gene was also observed to show leaky activity. However, there was no unique pattern as observed with that of TA29. Further, in the study we also show that while the smaller (290 bp) length of TA29 URM can be used to drive the expression of barnase gene to develop male sterile lines, it adversely affects the regeneration of transgenic tobacco lines due to leaky expression. This adverse effect is significantly reduced when the full length (1.5 kb) URM of the TA29 gene is used.     

Glycerol-3-phosphate levels are associated with basal resistance to the hemibiotrophic fungus Colletotrichum higginsianum in Arabidopsis

Glycerol-3-phosphate (G3P) is an important component of carbohydrate and lipid metabolic processes. In this article, we provide evidence that G3P levels in plants are associated with defense to a hemibiotrophic fungal pathogen Colletotrichum higginsianum. Inoculation of Arabidopsis (Arabidopsis thaliana) with C. higginsianum was correlated with an increase in G3P levels and a concomitant decrease in glycerol levels in the host. Plants impaired in utilization of plastidial G3P (act1) accumulated elevated levels of pathogen-induced G3P and displayed enhanced resistance. Furthermore, overexpression of the host GLY1 gene, which encodes a G3P dehydrogenase (G3Pdh), conferred enhanced resistance. In contrast, the gly1 mutant accumulated reduced levels of G3P after pathogen inoculation and showed enhanced susceptibility to C. higginsianum. Unlike gly1, a mutation in a cytosolic isoform of G3Pdh did not alter basal resistance to C. higginsianum. Furthermore, act1 gly1 double-mutant plants were as susceptible as the gly1 plants. Increased resistance or susceptibility of act1 and gly1 plants to C. higginsianum, respectively, was not due to effects of these mutations on salicylic acid- or ethylene-mediated defense pathways. The act1 mutation restored a wild-type-like response in camalexin-deficient pad3 plants, which were hypersusceptible to C. higginsianum. These data suggest that G3P-associated resistance to C. higginsianum occurs independently or downstream of the camalexin pathway. Together, these results suggest a novel and specific link between G3P metabolism and plant defense.     

Toxicological implications of a commercial formulation of deltamethrin (Decis®) in developing chick embryo

A deltamethrin containing insecticide formulation (Decis®) was evaluated for its toxic potential in developing chick embryos. For the present study, three water emulsified concentrations of Decis® (12.5 mg L^?1, 25 mg L^?1, and 50 mg L^?1) were used. Fertilized eggs of Gallus domesticus were immersed in these three concentrations of the insecticide for 60 min at 37°C on day 0 of incubation and kept for incubation till embryonic day 7. Recovered embryos were evaluated for teratogenic and biochemical changes. The results revealed that administration of Decis® at its lower concentrations (12.5 mg L^?1 and 25 mg L^?1) did not show any significant teratological changes but the significant number of abnormal survivors was observed at 50 mg L^?1 of dose concentration when compared with vehicle-treated control. Among biochemical changes, total glycogen and RNA contents of embryos was significantly decreased at 25 mg L^?1 and 50 mg L^?1 of Decis® concentrations. Similarly, significant alteration (p ≤ .05) was observed in alanine transaminase activity at 50 mg L^?1 concentration of Decis®. Thus, the present study concluded that the no-effect-level for developmental toxicity for Decis® is below the concentration of 25 mg L^?1 under standard laboratory conditions.     

Production of xylanase by immobilized Trichoderma reesei SAF3 in Ca-alginate beads

In the present study, the optimum conditions for the production of xylanase by immobilized spores of Trichoderma reesei SAF3 in calcium alginate beads were determined. The operational stability of the beads during xylanase production under semi-continuous fermentation was also studied. The influence of alginate concentration (1, 2, 3, and 4%) and initial cell loading (100, 200, 300, 400, and 500 beads per flask) on xylanase production was considered. The production of xylanase was found to increase significantly with increasing concentration of alginate and reached a maximum yield of 3.12 ± 0.18 U ml⁻¹ at 2% (w/v). The immobilized cells produced xylanase consistently up to 10 cycles and reached a maximum level at the forth cycle (3.36 ± 0.2 U ml⁻¹).     

Theoretical investigation on the kinetics and branching ratio of the gas phase reaction of sevoflurane with Cl atom

The present work deals with the theoretical investigation on the Cl initiated H-atom abstraction reaction of sevoflurane, (CF₃)₂CHOCH₂F. A dual-level procedure has been adopted for studying the kinetics of the reaction. Geometrical optimization and frequency calculation were performed at DFT(BHandHLYP)/6-311G(d,p) while single-point energy calculation was made at CCSD(T)/6-311G(d,p) level of theory. The intrinsic reaction coordinate (IRC) calculation has also been performed to confirm the smooth transition from the reactant to product through the respective transition state. The rate constants were calculated using conventional transition state theory (TST). It has been found that 99 % of the reaction proceeded via the H-atom abstraction from the –CH₂F end of the sevoflurane. The rate constant of the dominant path is found to be 1.13 × 10^?13 cm³ molecule^?1 s^?1. This is in excellent agreement with the reported experimental rate constant of 1.10 × 10^?13 cm³ molecule^?1 s^?1 obtained by relative rate method using FTIR/Smog chamber and LP/LIF techniques.     

Enhancement of catalase activity by repetitive low-grade H2O2 exposures protects fibroblasts from subsequent stress-induced apoptosis

Exposure of Chinese hamster V79 fibroblasts to mild and repetitive H2O2 doses in culture for 15 weeks produced no change in lipid peroxidation status, GSH/GSSG ratio and glutathione peroxidase activity of these cells (VST cells). In contrast, in VST cells catalase levels underwent a prominent increase which could be significantly inhibited and brought down to control levels after treatment with the catalase inhibitor 3-aminotriazole (3-AT). When control (VC) cells were exposed to UV radiation (UVC 5 J/m2) or H2O2 (7.5mM, 15 min), intracellular reactive oxygen species (ROS) levels rose prominently with significant activation of caspase-3. Marked nuclear fragmentation and lower cell viability were also noted in these cells. In contrast, VST cells demonstrated a significantly lower ROS level, an absence of nuclear fragmentation and an unchanged caspase-3 activity after exposure to UVC or H2O2. Cell viability was also significantly better preserved in VST cells than VC cells after UV or H2O2 exposures. Following 3-AT treatment of VST cells, UVC radiation or H2O2 brought about significantly higher elevations in intracellular ROS, increases in caspase-3 activity, significantly lowered cell viability and marked nuclear fragmentation, indicating the involvement of high catalase levels in the cytoprotective effects of repetitive stress. Therefore, upregulation of the antioxidant defense after repetitive oxidative stress imparted a superior ability to cope with subsequent acute stress and escape apoptotic death and loss of viability.     

Self-rotation of red blood cells in optical tweezers: prospects for high throughput malaria diagnosis

A simple and sensitive approach for detection of malarial parasite in blood samples is demonstrated. The approach exploits our finding that, in hypertonic buffer, a normal red blood cell (RBC) rotates by itself when trapped by an optical tweezers. The rotational speed increases linearly at lower trap-beam powers and more rapidly at higher powers. In contrast, under the same experimental conditions, RBC having a malarial parasite does not rotate. The rotational speeds of other RBCs from malaria-infected sample are of an order of magnitude less than that for normal RBC and also increase much more slowly with an increase in trap beam power than that for normal RBC. The difference in rotational speeds could be exploited for the diagnosis of malaria.