A plant miRNA contributes to antibacterial resistance by repressing auxin signaling

Plants and animals activate defenses after perceiving pathogen-associated molecular patterns (PAMPs) such as bacterial flagellin. In Arabidopsis, perception of flagellin increases resistance to the bacterium Pseudomonas syringae, although the molecular mechanisms involved remain elusive. Here, we show that a flagellin-derived peptide induces a plant microRNA (miRNA) that negatively regulates messenger RNAs for the F-box auxin receptors TIR1, AFB2, and AFB3. Repression of auxin signaling restricts P. syringae growth, implicating auxin in disease susceptibility and miRNA-mediated suppression of auxin signaling in resistance.     

The embryonic vertebrate heart tube is a dynamic suction pump

The embryonic vertebrate heart begins pumping blood long before the development of discernable chambers and valves. At these early stages, the heart tube has been described as a peristaltic pump. Recent advances in confocal laser scanning microscopy and four-dimensional visualization have warranted another look at early cardiac structure and function. We examined the movement of cells in the embryonic zebrafish heart tube and the flow of blood through the heart and obtained results that contradict peristalsis as a pumping mechanism in the embryonic heart. We propose a more likely explanation of early cardiac dynamics in which the pumping action results from suction due to elastic wave propagation in the heart tube.     

New strategies for the elimination of polio from India

The feasibility of global polio eradication is being questioned as a result of continued transmission in a few localities that act as sources for outbreaks elsewhere. Perhaps the greatest challenge is in India, where transmission has persisted in Uttar Pradesh and Bihar despite high coverage with multiple doses of vaccine. We estimate key parameters governing the seasonal epidemics in these areas and show that high population density and poor sanitation cause persistence by not only facilitating transmission of poliovirus but also severely compromising the efficacy of the trivalent vaccine. We analyze strategies to counteract this and show that switching to monovalent vaccine may finally interrupt virus transmission.     

Baseline toxicity and stage specificity of recently developed reduced‐risk insecticides chlorantraniliprole and spinetoram to obliquebanded leafroller,Choristoneura rosaceana (Harris) (Lepidoptera: Tortricidae)

BACKGROUND: Studies were designed to assess baseline toxicity of the two recently developed reduced‐risk insecticides chlorantraniliprole and spinetoram to obliquebanded leafroller (OBLR), Choristoneura rosaceana (Harris), and to determine stage‐specific effects of these products on OBLR, so that these new chemicals could be judiciously incorporated into IPM programs by targeting only the most susceptible stages of OBLR. RESULTS: Both chlorantraniliprole and spinetoram were highly effective against neonate OBLR larvae at much lower doses than conventional standard azinphosmethyl. Most of the mortality caused by spinetoram occurred during the 4 day exposure period, while significant delayed mortality was observed as a result of chlorantraniliprole treatment during the 7 day recovery period, indicating that chlorantraniliprole is a slower‐acting compound compared with spinetoram. Unlike broad‐spectrum predecessors, the toxicity of chlorantraniliprole significantly increased with larval age. Similarly, the toxicity of spinetoram increased as larvae grew from neonates to third instars. CONCLUSION: Chlorantraniliprole and spinetoram are highly effective against OBLR larvae, regardless of larval age. Incorporation of these reduced‐risk chemistries into IPM programs for OBLR would lead to effective management of this pest in tree fruit systems. Copyright © 2011 Society of Chemical Industry     

Increase in growth,productivity and nutritional status of rice (<Emphasis Type="Italic">Oryza sativa</Emphasis> L. cv. Basmati) and enrichment in soil fertility applied with an organic matrix entrapped urea

Field experiments were conducted to evaluate the effects of eco-friendly organic matrix entrapped urea (OMEU) on growth, productivity, and yield of rice (Oryza sativa L. cv. Basmati) and soil enrichment in the paddy field at Rohtak (Haryana) located near Delhi. The OMEU prepared in granular form contained cow dung, rice bran (grain cover of Oryza sativa), powder of neem leaves (Azadirachta indica), and clay soil (diameter of particles < 0.02 mm) in 1:1:1:1 ratios and saresh (plant gum of Acacia sp.) as binder along with half of the recommended dose of commercially available soluble urea (free urea; FU). Single basal application of OMEU showed an increase in plant growth in terms of fresh and dry weights, root length, root, leaf and tiller numbers, soluble protein, total N and ammonium in leaves, productivity in terms of grain and straw yield, and nutritional and microbial activities of field soil over free form of urea and no fertilizer application. Nutritional status of rice grains was also improved over the free urea and no fertilizer controls. Our data indicate that OMEU, which is low cost and based on bio-degradable, non-toxic, and locally available agro-waste, can be attempted to replace the conventional use of soluble urea in rice.     

Single and joint acute toxicity of isocarbophos enantiomers to Daphnia magna

Although enantioselectivity in the toxicity of chiral pesticides has received considerable attention over recent years, how coexisting enantiomers interact with each other during their toxic action remains unknown. In this study, we attempted to resolve the enantiomers of a chiral organophosphate insecticide, isocarbophos, and investigated the acute toxicity of individual enantiomers and various enantiomer mixtures. Baseline enantiomeric separation of isocarbophos was achieved on a Chiralcel OD column with the mobile phase of n-hexane/isopropanol (90/10, v/v) at a flow rate of 0.8 mL/min. The resolved enantiomers were differentiated by their responses on a circular dichroism detector. The median lethal concentrations (LC 50) of racemate, (+)-enantiomer, and (-)-enantiomer of isocarbophos toward Daphnia magna were 13.9, 7.08, and 353 microg/L, respectively, after 48 h of static exposure, displaying a 50-fold difference between the enantiomers. Toxic unit (TU) analysis was employed to evaluate the joint toxicity of isocarbophos enantiomer mixtures. The calculated TU mix for the acute toxicity (48 h test) of various binary mixtures ranged from 0.83 to 1.04, suggesting a mode of additive effect. Further evaluation of available literature data for chiral organophosphorus insecticides showed that the joint toxicity of enantiomers may be additive, synergistic, and antagonistic. Therefore, when significant enantioselectivity exists for a chiral pesticide, it is important to also evaluate the interaction of enantiomers in the joint toxicity effect when enantiomers are present in a mixture.     

Transformation and sorption of fipronil in urban stream sediments

Fipronil is an urban-use insecticide, and the increased use has led to its frequent detections in urban streams. Most studies on the environmental fate of fipronil so far have focused on soils, and little is known about its behavior in sediment-water systems. In this study, we investigated the transformation and sorption of fipronil in urban stream sediments from California, incubated under facultative and anaerobic conditions. Degradation of fipronil in sediments generally followed exponential decay kinetics, and the first-order half-lives of fipronil were only 4.6-18.5 days in anaerobic sediments. The persistence of fipronil under facultative conditions was considerably longer, with half-lives from 25 to 91 days. Sterilization generally decreased the dissipation of fipronil, indicating that microbial activity was an important factor in fipronil transformations in sediments. Under facultative conditions, fipronil sulfide and sulfone were observed, while only fipronil sulfide was detected in anaerobic samples. The sorption coefficient K d consistently increased with organic carbon contents of sediments. In the same sediment, K d usually also increased with contact time, suggesting decreased availability for aged residues. Results from this study showed that the stability of fipronil in sediments depends closely on the oxygen status and that due to the readily conversion of fipronil to the sulfone and sulfide metabolites, the overall risk assessment of fipronil in surface aquatic systems should take into consideration fipronil as well as its metabolites.     

Optimization of an oxygen-based approach for community-level physiological profiling of soils

Current approaches for rapid assessment of carbon source utilization by whole soil communities (i.e., community-level physiological profiling or CLPP) provide a limited, biased view of microbial communities with little connection to in situ activities. We developed an alternative CLPP approach based upon fluorometric detection of dissolved oxygen consumption in a microtiter platform which offers flexible manipulation of experimental factors. In the attempt to reduce oxygen re-dissolution, the wells were filled with liquid to very near the top and sealed. We found that filling the wells with 240 vs. 150 μl of sample improved the sensitivity of the system to discern both the response to a substrate amendment as low as 10 mg l⁻¹ and un-amended, endogenous respiration. The preparation of a soil slurry facilitates inoculation into the microplate. Disruption of soil samples had a limited effect on the endogenous respiration in comparison to intact soil microbags in a 24-well microplate. Storage time (up to 33 days) reduced the level of activity in intact soil microbags but not in disrupted samples. A microcosm fertilization experiment was set to study the effects of N availability on the respiratory response in the plates. The use of soil organic carbon (SOC) and amended C-substrates (50 mg l⁻¹) was increased by the addition of nitrogen (N) in the plate, and appeared N-limited shortly after microcosm fertilization. The addition of the eukaryotic inhibitor cycloheximide delayed the initial increase in fluorescence (time to minimum response) of several C sources (casein, acetate, asparagine, coumaric acid), varying among soils, which could be explained by the fungal use of these compounds. However, the extent of the inhibition caused by cycloheximide did not increase at higher fungal to bacteria ratios as estimated by PLFA analysis, indicating that the direct estimation of the fungal biomass from cycloheximide addition is not feasible. This paper provides an optimized, standardized protocol for soil analysis, and sets the basis for further validation studies that will continue to define the underlying capabilities/biases of this approach.