Intercropping impacts the host location behaviour and population growth of aphids

Increasing intrafield plant diversity has been shown to regulate pest populations in various agroecosystems. Among the suggested mechanisms for this bottom-up pest control, the disruptive crop hypothesis states that herbivores' abilities to locate and colonize their host plants are reduced by the presence of non-host plants. Under laboratory conditions, we evaluated how intercropping wheat and legumes modifies the behaviour of apterous cereal aphids, Sitobion avenae (Fabricius) (Hemiptera: Aphididae), in terms of host plant location and population growth. We compared two intercropping systems – soft winter wheat, Triticum aestivum L. (Poaceae), associated with winter pea, Pisum sativum L., or with white clover, Trifolium repens L. (both Fabaceae) – and sole stands of soft winter wheat. Aphids needed more time to locate their wheat host plant and then spent less time on wheat when it was intercropped with clover. At the population level, and accounting for host plant biomass, only intercropping wheat with clover significantly reduced aphid densities on wheat, as this was particularly disruptive to S. avenae behaviour and population growth. Our laboratory study points out that the species used as non-host plants and their density are important parameters that should be taken into account in field studies on intercropping systems.     

Phenology of the black bean aphid,Aphis fabae,on organic crops and effect of parasitoid communities

1. Parasitoids represent the third trophic level in plant-insect food webs. They develop in or on herbivorous insects at the second trophic level, which in turn feed on plants that constitute the first trophic level. This food web system might be affected by agricultural landscape and practices.
2. We studied the phenology and population density of Aphis fabae (Hemiptera: Aphididae) and determined the impact of parasitoids in organic fields of beans and beet plants.
3. Twenty leaves per field were collected weekly. For each leaf, the total number of aphids, apterous and alate morphs, the number of mummies, and mortality of aphids were recorded.
4. Our results showed that the phenology of A. fabae varied throughout the season with maximal numbers observed at the beginning of summer. In addition, the production of alate morphs and the proportion of parasitism were positively correlated to an increase in aphid densities.
5. Six parasitoid species were recorded attacking A. fabae in the field, with Lysiphlebus fabarum and Binodoxys angelicae (Hymenoptera: Aphidiinae) being the most abundant parasitoids.
6. Field characteristics and availability of host plants in the surroundings affected A. fabae density. Lysiphlebus fabarum and B. angelicae appeared to be good biocontrol candidates against A. fabae.

     

Functional characterization of isolated RNA-binding domains of the GRSF1 protein

The Guanine-rich RNA sequence binding factor 1 (GRSF1) is a member of the heterogeneous nuclear ribonucleoprotein F/H family and has been implicated in RNA processing, RNA transport and translational regulation. Amino acid alignments and homology modeling suggested the existence of three distinct RNA-binding domains and two auxiliary domains. Unfortunately, little is known about the molecular details of GRSF1/RNA interactions. To explore the RNA-binding mechanisms we first expressed full-length human GRSF1 and several truncation mutants, which include the three separated qRRM domains in E. coli, purified the recombinant proteins and quantified their RNA-binding affinity by RNA electrophoretic mobility shift assays. The expression levels varied between 1 and 10 mg purified protein per L bacterial liquid culture and for full-length human GRSF1 a binding constant (K_D-value) of 0.5 μM was determined. In addition, our mechanistic experiments with different truncation mutants allowed the following conclusions: i) Deletion of either of the three RNA-binding domains impaired the RNA-binding affinity suggesting that the simultaneous presence of the three domains is essential for high-affinity RNA-binding. ii) Deletion of the Ala-rich auxiliary domain did hardly affect RNA-binding. Thus, this structural subunit may not be involved in RNA interaction. iii) Deletion of the acidic auxiliary domain improved the RNA-binding suggesting a regulatory role for this structural motif. iv) The isolated RNA-binding domains did not exhibit sizeable RNA-binding affinities. Taken together these data suggest that a cooperative interaction of the three qRRMs is required for high affinity RNA-binding.     

Di-phosphorylated BAF shows altered structural dynamics and binding to DNA,but interacts with its nuclear envelope partners

Barrier-to-autointegration factor (BAF), encoded by the BANF1 gene, is an abundant and ubiquitously expressed metazoan protein that has multiple functions during the cell cycle. Through its ability to cross-bridge two double-stranded DNA (dsDNA), it favours chromosome compaction, participates in post-mitotic nuclear envelope reassembly and is essential for the repair of large nuclear ruptures. BAF forms a ternary complex with the nuclear envelope proteins lamin A/C and emerin, and its interaction with lamin A/C is defective in patients with recessive accelerated aging syndromes. Phosphorylation of BAF by the vaccinia-related kinase 1 (VRK1) is a key regulator of BAF localization and function. Here, we demonstrate that VRK1 successively phosphorylates BAF on Ser4 and Thr3. The crystal structures of BAF before and after phosphorylation are extremely similar. However, in solution, the extensive flexibility of the N-terminal helix α1 and loop α1α2 in BAF is strongly reduced in di-phosphorylated BAF, due to interactions between the phosphorylated residues and the positively charged C-terminal helix α6. These regions are involved in DNA and lamin A/C binding. Consistently, phosphorylation causes a 5000-fold loss of affinity for dsDNA. However, it does not impair binding to lamin A/C Igfold domain and emerin nucleoplasmic region, which leaves open the question of the regulation of these interactions.     

HLA-C “blank” alleles express class I gene products. Biochemical analysis of four different HLA-C “blank” polypeptides

Monoclonal antibodies (mAbs) W6/32, HC10, and 4E were used to precipitate class I antigens from 21 selected individuals with at least oneHLA-C “blank” allele. In 19 of these individuals, characteristicHLA-C banding patterns which could be precipitated by all three HLA class I mAbs were observed on one-dimensional isoelectric focusing gels-obviously the gene products ofHLA-C “blank”. At least four allelic HLA-C “blank” gene products with different isoelectric points could be discerned. All of them segregated withHLA-C “blank” haplotypes in informative families; two of them were associated withHLA-B51, one withHLA-B38, and one withHLA-B18. Reactivity of the HLA-C “blank” heavy chains with mAb W6/32 indicates that they are able to associated with beta-2 microglobulin, and hence are most probably expressed at the cell surface.     

No Country for Old Men

Within affluent societies, people who grow up in deprived areas begin reproduction much earlier than their affluent peers, and they display a number of other behaviors adapted to an environment in which life will be short. The psychological mechanisms regulating life-history strategies may be sensitive to the age profile of the people encountered during everyday activities. We hypothesized that this age profile might differ between environments of different socioeconomic composition. We tested this hypothesis with a simple observational study comparing the estimated age distribution of people using the streets in an affluent and a socioeconomically deprived neighborhood which were closely matched in other ways. We were also able to use the UK census to compare the age profile of observed street users with the actual age profile of the community. We found that people over 60?years of age were strikingly less often observed on the street in the deprived than in the affluent neighborhood, whereas young adults were observed more often. These differences were not reflections of the different age profiles of people who lived there, but rather of differences in which residents use the streets. The way people use the streets varies with age in different ways in the affluent and the deprived neighborhoods. We argue that chronic exposure to a world where there are many visible young adults and few visible old ones may activate psychological mechanisms that produce fast life-history strategies.     

An improved method to monitor the health of seagrass meadows based on kriging

This paper focuses on the spatial pattern of the shoot density of the seagrass Posidonia oceanica through kriging methods. Kriging is a group of geostatistical techniques to predict the value of a field at an unobserved location from observations of its value at nearby locations. The results of an ordinary kriging of both raw values of shoot density and normalized shoot density with reference to a density vs. depth model (Dn) were compared. Results confirmed the existence of spatially organized parameters other than depth that influence patterns of P. oceanica shoot density. Although still requiring additional testing for complete validation, Dn mapping appears to be a valuable tool to (1) infer causes for the meadow's condition and to design a cost-effective field survey; (2) define areas where protection policies should be undertaken.