Birnavirus precursor polyprotein is processed in Escherichia coli by its own virus-encoded polypeptide.

The cDNA fragment of the large RNA segment of infectious bursal disease virus 002-73, when expressed in Escherichia coli, produces precursor polyprotein (N-VP2-VP4-VP3-C), most of which is then processed to generate constituent polypeptides. Using cDNA fragments containing site-specific mutations and two monoclonal antibodies that are specific to VP2 and VP3 of mature virus particles, we demonstrated that the VP4 protein is involved in processing of the precursor polyprotein to generate VP2 and VP3 and excluded the possibility of internal initiation for the generation of VP3.     

High vapor pressure deficit drives salt‐stress‐induced rice yield losses in India

Flooded rice is grown across wide geographic boundaries from as far north as Manchuria and as far south as Uruguay and New South Wales, primarily because of its adaptability across diverse agronomic and climatic conditions. Salt‐stress damage, a common occurrence in delta and coastal rice production zones, could be heightened by the interactions between high temperature and relative humidity (vapor pressure deficit – VPD). Using temporal and spatial observations spanning 107 seasons and 19 rice‐growing locations throughout India with varying electrical conductivity (EC), including coastal saline, inland saline, and alkaline soils, we quantified the proportion of VPD inducing salinity damage in rice. While controlling for time‐invariant factors such as trial locations, rice cultivars, and soil types, our regression analysis indicates that EC has a nonlinear detrimental effect on paddy rice yield. Our estimates suggest these yield reductions become larger at higher VPD. A one standard deviation (SD) increase in EC from its mean value is associated with 1.68% and 4.13% yield reductions at median and maximum observed VPD levels, respectively. Yield reductions increase roughly sixfold when the one SD increase is taken from the 75th percentile of EC. In combination, high EC and VPD generate near catastrophic crop loss as predicted yield approaches zero. If higher VPD levels driven by global warming materialize in conjunction with rising sea levels or salinity incursion in groundwater, this interaction becomes an important and necessary predictor of expected yield losses and global food security.     

Effect of elevated CO2 and high temperature on seed-set and grain quality of rice

Hybrid vigour may help overcome the negative effects of climate change in rice. A popular rice hybrid (IR75217H), a heat-tolerant check (N22), and a mega-variety (IR64) were tested for tolerance of seed-set and grain quality to high-temperature stress at anthesis at ambient and elevated [CO(2)]. Under an ambient air temperature of 29 °C (tissue temperature 28.3 °C), elevated [CO(2)] increased vegetative and reproductive growth, including seed yield in all three genotypes. Seed-set was reduced by high temperature in all three genotypes, with the hybrid and IR64 equally affected and twice as sensitive as the tolerant cultivar N22. No interaction occurred between temperature and [CO(2)] for seed-set. The hybrid had significantly more anthesed spikelets at all temperatures than IR64 and at 29 °C this resulted in a large yield advantage. At 35 °C (tissue temperature 32.9 °C) the hybrid had a higher seed yield than IR64 due to the higher spikelet number, but at 38 °C (tissue temperature 34-35 °C) there was no yield advantage. Grain gel consistency in the hybrid and IR64 was reduced by high temperatures only at elevated [CO(2)], while the percentage of broken grains increased from 10% at 29 °C to 35% at 38 °C in the hybrid. It is concluded that seed-set of hybrids is susceptible to short episodes of high temperature during anthesis, but that at intermediate tissue temperatures of 32.9 °C higher spikelet number (yield potential) of the hybrid can compensate to some extent. If the heat tolerance from N22 or other tolerant donors could be transferred into hybrids, yield could be maintained under the higher temperatures predicted with climate change.     

Synthesis and characterization of a Eu-DTPA-PEGO-MSH(4) derivative for evaluation of binding of multivalent molecules to melanocortin receptors

A labeled variant of MSH(4), a tetrapeptide that binds to the human melanocortin 4 receptor (hMC4R) with low μM affinity, was prepared by solid-phase synthesis methods, purified, and characterized. The labeled ligand, Eu-DTPA-PEGO-His-dPhe-Arg-Trp-NH₂, exhibited a K_d for hMC4R of 9.1 ± 1.4 μM, approximately 10-fold lower affinity than the parental ligand. The labeled MSH(4) derivative was employed in a competitive binding assay to characterize the interactions of hMC4R with monovalent and divalent MSH(4) constructs derived from squalene. The results were compared with results from a similar assay that employed a more potent labeled ligand, Eu-DTPA-NDP-α-MSH. While results from the latter assay reflected only statistical effects, results from the former assay reflected a mixture of statistical, proximity, and/or cooperative binding effects.     

Environmental surveillance system to track wild poliovirus transmission

Eradication of poliomyelitis from large metropolis cities in India has been difficult due to high population density and the presence of large urban slums. Three paralytic poliomyelitis cases were reported in Mumbai, India, in 1999 and 2000 in spite of high immunization coverage and good-quality supplementary immunization activities. We therefore established a systematic environmental surveillance study by weekly screening of sewage samples from three high-risk slum areas to detect the silent transmission of wild poliovirus. In 2001, from among the 137 sewage samples tested, wild poliovirus type 1 was isolated from 35 and wild poliovirus type 3 was isolated from 1. Acute flaccid paralysis (AFP) surveillance indicated one case of paralytic poliomyelitis from the city. Phylogenetic analysis with complete VP1 sequences revealed that the isolates from environmental samples belonged to four lineages of wild polioviruses recently isolated from poliomyelitis cases in Uttar Pradesh and not to those previously isolated from AFP cases in Mumbai. Wild poliovirus thus introduced caused one case of paralytic poliomyelitis. The virus was detected in environmental samples 3 months before. It was found that wild polioviruses introduced several times during the year circulated in Mumbai for a limited period before being eliminated. Environmental surveillance was found to be sensitive for the detection of wild poliovirus silent transmission. Nucleotide sequence analysis helped identify wild poliovirus reservoir areas.     

Brinckochrysa scelestes [Neur.: Chrysopidae] as predator ofMyzus persicae [Hom.: Aphididae] on tobacco

Laboratory and field studies were conducted to study the suitability and efficacy ofBrinckochrysa scelestes Banks as a predator onMyzus persicae Sulzer in tobacco fields. Laboratory bred 2nd instar larvae ofB. scelestes at 6 per tobacco plant reduced the aphid population to the extent of 78% in 2 weeks. The movement of the predatory larvae on the tobacco plant and leaf was not at all hampered by the glandular trichomes and their secretions. The larvae moved freely and fed well and their pupae were recovered from all over the plant.

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Résumé On étudie en laboratoire et en champ de tabac la valeur et l'efficacité deBrinckchrysa scelestes Banks comme agent de lutte biologique contreMyzus persicae Sulzer. Les larves du 2ème stade élevées en laboratoire de ce chrysope à raison de 6 par plante sont les plus actives et réduisent la population de pucerons de 78% en 2 semaines. Les sécrétions des trichomes des feuilles de tabac n'ont pas d'effet sur les larves ni sur leurs mouvements. Les larves se déplacent librement et se nourissent bien; des nymphes ont été trouvées sur tous les plants, ce qui indique que le prédateur est valable contreM. persicae et bien adapté à la culture de tabac.

     

Diffusion, Transport, and Cell Membrane Organization Investigated by Imaging Fluorescence Cross-Correlation Spectroscopy

Cell membrane organization is dynamic and is assumed to have different characteristic length scales. These length scales, which are influenced by lipid and protein composition as well as by the cytoskeleton, can range from below the optical resolution limit (as with rafts or microdomains) to far above the resolution limit (as with capping phenomena or the formation of lipid “platforms”). The measurement of these membrane features poses a significant problem because membrane dynamics are on the millisecond timescale and are thus beyond the time resolution of conventional imaging approaches. Fluorescence correlation spectroscopy (FCS), a widely used spectroscopic technique to measure membrane dynamics, has the required time resolution but lacks imaging capabilities. A promising solution is the recently introduced method known as imaging total internal reflection (ITIR)-FCS, which can probe diffusion phenomena in lipid membranes with good temporal and spatial resolution. In this work, we extend ITIR-FCS to perform ITIR fluorescence cross-correlation spectroscopy (ITIR-FCCS) between pixel areas of arbitrary shape and derive a generalized expression that is applicable to active transport and diffusion. ITIR-FCCS is applied to model systems exhibiting diffusion, active transport, or a combination of the two. To demonstrate its applicability to live cells, we observe the diffusion of a marker, the sphingolipid-binding domain (SBD) derived from the amyloid peptide Aβ, on live neuroblastoma cells. We investigate the organization and dynamics of SBD-bound lipid microdomains under the conditions of cholesterol removal and cytoskeleton disruption.