Does the presence of grassy strips and landscape grain affect the spatial distribution of aphids and their carabid predators?

• 1 We investigated, over the course of 2 years, the spatial distribution and abundance of two species of aphid, Metopolophium dirhodum and Sitobion avenae, and predatory species of carabid. This was undertaken in 24 wheat fields in ‘coarse‐grain’ and ‘fine‐grain’ landscapes in western France. A greater percentage of the latter landscape was covered by hedgerows and grassland and the total area covered by fields and the average size of the fields were smaller.
• 2 The effects on aphid abundance of the distance from field margins, the presence of grassy strips and carabid abundance were determined in both landscapes.
• 3 Both aphid species were more abundant in the ‘fine‐grain’ landscape, which may have been a result of the higher density of semi‐natural elements. In both types of landscape, the total numbers of aphids were negatively correlated with the distance from the field margin. This may have been because aphids were dispersing from overwintering sites in field margins. The abundance of M. dirhodum was strongly negatively correlated with the presence of grassy strips in the ‘coarse‐grain’ landscape, although there were no such significant correlations for either of the aphid species in the ‘fine‐grain’ landscape.
• 4 Aphid and carabid abundances were negatively correlated in the ‘fine‐grain’ and positively in ‘coarse‐grain’ landscape.
• 5 The results obtained in the present study emphasize the importance of semi‐natural areas in agricultural landscapes in shaping the spatial distribution of aphids and carabid beetles, their natural enemies, at different spatial scales.

     

Urea’s Effect on the Ribonuclease A Catalytic Efficiency: A Kinetic, 1H NMR and Molecular Orbital Study

Understanding of protein–urea interactions is one of the greatest challenges to modern structural protein chemistry. Based in enzyme kinetics experiments and ¹H NMR spectroscopic analysis we proposed that urea, at low concentrations, directly interacts with the protonated histidines of the active center of RNase A, following a simple model of competitive inhibition. These results were supported by theoretical analysis based on the frontier molecular orbital theory and suggest that urea might establish a favorable interaction with the cationic amino acids. Our experimental evidence and theoretical analysis indicate that the initials steps of the molecular mechanism of Urea–RNase A interaction passes through the establishment of a three center four electron adduct. Also, our results would explain the observed disruption of the ¹H NMR signals corresponding to H12 and H119 (involved in catalysis) of the RNase A studied in the presence of urea. Our interaction model of urea–amino acids (cationic) can be extended to explain the inactivation of other enzymes with cationic amino acids at the active site.     

Characterisation of a novel Emaravirus identified in mosaic-diseased Eurasian aspen (Populus tremula)

Since Emaraviruses have been discovered in 2007 several new species were detected in a range of host plants. Five genome segments of a novel Emaravirus from mosaic-diseased Eurasian aspen (Populus tremula) have been completely determined. The monocistronic, segmented ssRNA genome of the virus shows a genome organisation typical for Emaraviruses encoding the viral RNA-dependent RNA polymerase (RdRP, 268.2 kDa) on RNA1 (7.1 kb), a glycoprotein precursor (GPP, 73.5 kDa) on RNA2 (2.3 kb), the viral nucleocapsid protein (N, 35.6 kDa) on RNA3 (1.6 kb), and a putative movement protein (MP, 41.0 kDa) on RNA4 (1.6 kb). The fifth identified genome segment (RNA5, 1.3 kb) encodes a protein of unknown function (P28, 28.1 kDa). We discovered that it is distantly related to proteins encoded by Emaraviruses, such as P4 of European mountain ash ringspot-associated virus. All proteins from this group contain a central hydrophobic region with a conserved secondary structure and a hydrophobic amino acid stretch, bordered by two highly conserved positions, thus clearly representing a new group of homologues of Emaraviruses. The virus identified in Eurasian aspen is closely associated with observed leaf symptoms, such as mottle, yellow blotching, variegation and chloroses along veins. All five viral RNAs were regularly detectable by RT-PCR in mosaic-diseased P. tremula in Norway, Finland and Sweden (Fennoscandia). Observed symptoms and testing of mosaic-diseased Eurasian aspen by virus-specific RT-PCR targeting RNA3 and RNA4 confirmed a wide geographic distribution of the virus in Fennoscandia. We could demonstrate that the mosaic-disease is graft-transmissible and confirmed that the virus is the causal agent by detection in symptomatic, graft-inoculated seedlings used as rootstocks as well as in the virus-infected scions used for graft-inoculation. Owing to these characteristics, the virus represents a novel species within the genus Emaravirus and was tentatively denominated aspen mosaic-associated virus.     

Evaluation of phylogenetic relationship between three phenotypically different forms of Red date palm weevil Rhynchophorus ferrugineus Oliv. using PCR-based RAPD technique

Abstract

Red date palm weevil Rhynchophorus ferrugineus Oliv. is a widespread major pest of date palm in the Kingdom of Saudi Arabia. Three different forms (black and brown with and without spots on thoracic region) were investigated using PCR-based RAPD technique. Although weevils were collected from the same geographical region of Al-Hassa in Saudi Arabia, the banding profile acquired suggested that black and brown colored morphs are genetically closer compared to the brown with spots. Intra color variation remained minimum in black but brown and brown spotted morphs exhibited more genetic variation. This genetic variation may be either due to the generation of new mutants from the non-spotted or spotted weevil or they may belong to a different race.     

Microbial maceration and carbonate dissolution on cold‐temperate shelves

Nummulites beaumonti d'Archiac & Haime, 1853, originally described from El Basatin, Gebel Mokattam, Greater Cairo, is redefined from a nummulitic bank at the base of the Maadi Formation from its type locality as neotype. Schaub (1981) described the species from Libya and the type example of this species is still unknown. N. discorbinus Schlotheim (1820) is described as neotype from a nummulitic bank in the Mokattam Formation, which is located in the site of the Citadel tombs, near the Salah El Din Citadel, Gebel Mokattam, Egypt. According to Schaub (1981), the type example of this species is also unknown. For this reason the establishment of the neotypes of these two widespread nummulites species: N. discorbinus (Late Lutetian) and N. beaumonti (Bartonian) is important and tackled in this paper. N. qurnensis n. sp. ( = N. sp. cf. beaumonti in Boukhary et al. 2002) is introduced as a new species from the lower Bartonian part of the Qurn Formation of Helwan. Biometrical studies are carried out on the three species to present up to date information on these Nummulites, with particular attention to their biostratigraphic correlation with the Shallow Benthic Zones (SBZ) of Serra-Kiel et al. 1998. The authors would like to stress the importance of a careful designation of a neotype to avoid the introduction of complicated and unnecessary taxonomic problems.     

A dynamic metabolic flux balance based model of fed‐batch fermentation of bordetella pertussis

A mathematical model based on a dynamic metabolic flux balance (DMFB) is developed for a process of fed‐batch fermentation of Bordetella pertussis. The model is based on the maximization of growth rate at each time interval subject to stoichiometric constraints. The model is calibrated and verified with experimental data obtained in two different bioreactor experimental systems. It was found that the model calibration was mostly sensitive to the consumption or production rates of tyrosine and, for high supplementation rates, to the consumption rate of glutamate. Following this calibration the model correctly predicts biomass and by‐products concentrations for different supplementation rates. Comparisons of model predictions to oxygen uptake and carbon emission rates measurements indicate that the TCA cycle is fully functional. © 2013 American Institute of Chemical Engineers Biotechnol. Prog., 29: 520–531, 2013     

Emerging Role of Angiotensin Type 2 Receptor (AT2R)/Akt/NO Pathway in Vascular Smooth Muscle Cell in the Hyperthyroidism

Hyperthyroidism is characterized by increased vascular relaxation and decreased vascular contraction and is associated with augmented levels of triiodothyronine (T3) that contribute to the diminished systemic vascular resistance found in this condition. T3 leads to augmented NO production via PI3K/Akt signaling pathway, which in turn causes vascular smooth muscle cell (VSMC) relaxation; however, the underlying mechanisms involved remain largely unknown. Evidence from human and animal studies demonstrates that the renin-angiotensin system (RAS) plays a crucial role in vascular function and also mediates some of cardiovascular effects found during hyperthyroidism. Thus, in this study, we hypothesized that type 2 angiotensin II receptor (AT2R), a key component of RAS vasodilatory actions, mediates T3 induced-decreased vascular contraction. Marked induction of AT2R expression was observed in aortas from T3-induced hyperthyroid rats (Hyper). These vessels showed decreased protein levels of the contractile apparatus: α-actin, calponin and phosphorylated myosin light chain (p-MLC). Vascular reactivity studies showed that denuded aortic rings from Hyper rats exhibited decreased maximal contractile response to angiotensin II (AngII), which was attenuated in aortic rings pre-incubated with an AT2R blocker. Further study showed that cultured VSMC stimulated with T3 (0.1 µmol/L) for 24 hours had increased AT2R gene and protein expression. Augmented NO levels and decreased p-MLC levels were found in VSMC stimulated with T3, both of which were reversed by a PI3K/Akt inhibitor and AT2R blocker. These findings indicate for the first time that the AT2R/Akt/NO pathway contributes to decreased contractile responses in rat aorta, promoted by T3, and this mechanism is independent from the endothelium.