Persistence of occluded viruses in the nests of the paper waspPolistes hebraeus (Hym.: Vespidae)

Bioassays were used to study the infectivity of cytoplasmic polyhedrosis viruses (CPVs), nuclear polyhedrosis viruses (NPVs) and entomopoxviruses (EPVs) contained in 16 nests of the paper waspPolistes hebraues F. in Réunion Island. Several virosis were propagated from 6 nest contents in 5 Lepidoptera:Catopsilia thauruma Saalmüller,Catopsilia florella F.,Callixena versicolora Mabille,Polydesma umbricola Boisduval andEagris sabadius Boisduval. Each of the previous species supported the development of one or two virosis and therefore, wasp nests must be considered as accumulating centres where infectivity of occluded entomoviruses is preserved. The accurate origin of the virosis propagated through bioassays was searched for using ecological investigations on similar natural diseases, REN analysis and a cross-transmission test onSpodoptera mauritia Boisduval. The nuclear polyhedrosis and one cytoplasmic polyhedrosis appearing in bioassays can be assigned respectively to viruses produced byC. thauruma andC. versicolora; the other virosis must be considered as developing in alternate or substitution hosts. Wasp nests could therefore be used to detect the presence of specific viruses in an environment and to collect new virus isolates.     

PTPN21 exerts pro-neuronal survival and neuritic elongation via ErbB4/NRG3 signaling

Although expression quantitative trait locus, eQTL, serves as an explicit indicator of gene–gene associations, challenges remain to disentangle the mechanisms by which genetic variations alter gene expression. Here we combined eQTL and molecular analyses to identify an association between two seemingly non-associated genes in brain expression data from BXD inbred mice, namely Ptpn21 and Nrg3. Using biotinylated receptor tracking and immunoprecipitation analyses, we determined that PTPN21 de-phosphorylates the upstream receptor tyrosine kinase ErbB4 leading to the up-regulation of its downstream signaling. Conversely, kinase-dead ErbB4 (K751R) or phosphatase-dead PTPN21 (C1108S) mutants impede PTPN21-dependent signaling. Furthermore, PTPN21 also induced Elk-1 activation in embryonic cortical neurons and a novel Elk-1 binding motif was identified in a region located 1919 bp upstream of the NRG3 initiation codon. This enables PTPN21 to promote NRG3 expression through Elk-1, which provides a biochemical mechanism for the PTPN21–NRG3 association identified by eQTL. Biologically, PTPN21 positively influences cortical neuronal survival and, similar to Elk-1, it also enhances neuritic length. Our combined approaches show for the first time, a link between NRG3 and PTPN21 within a signaling cascade. This may explain why these two seemingly unrelated genes have previously been identified as risk genes for schizophrenia.     

Fate of transformed Trichoderma harzianum in the phylloplane of tomato plants

A propiconazole-resistant Trichoderma harzianum strain with high phylloplane survival capability was transformed with the E. coli hygromycin B phosphotransferase gene (hph), coding for hygromycin B resistance. Four transformants were analysed for survival ability on the phylloplane of tomato plants grown under glasshouse conditions in comparison with their prototype and a yellow, hygromycin B-sensitive mutant. Over 2 weeks, the four transformants showed higher survival rates in comparison with the wild-type strain. The yellow mutant TF3/973 did not significantly differ in survival from the transformants. Both hygromycin B resistance and mitotic stability of transformants were evaluated during growth in vitro and after reisolation from tomato phylloplane. Hybridization patterns with the complete plasmid indicated that all four transformants were mitotically stable after several rounds of vegetative growth without selective pressure and during 2 weeks on tomato plants. None of the transformants had lost the ability to grow in the presence of both propiconazole and hygromycin B after growth under the same conditions. The results are discussed in relation to risk assessment of the release of transgenic fungi.     

Survival costs of reproduction vary with age in North American red squirrels

The costs of reproduction are expected to be higher under unfavourable conditions, so that breeding in years of low food supply should have important costs. In addition, the costs of reproduction may be contingent on the age of individuals, and young growing and old senescent individuals should suffer higher costs than the prime-age ones. We tested these predictions by investigating the costs of reproduction as a function of food availability and age in female North American red squirrels using the long-term data on survival and reproduction. We found that the costs of reproduction were independent of food supply, and we did not detect any trade-off between the current and future reproduction. We also did not detect any survival cost of reproduction for the prime-age females, but found evidence for survival costs in yearlings and old (6 years or above) females with successfully breeding individuals having a lower chance of survival compared with unsuccessful or non-breeding ones. These results supported our prediction that the costs of reproduction depended on the age of female red squirrels and were higher in young growing and old senescent individuals. Our study also indicated that, in contrast to large herbivores, heterogeneity in individual quality and viability selection in red squirrels do not affect the study of trade-offs and of the age variation in life-history traits.     

Effects of Patch-Burn Management on Dickcissel Nest Success in a Tallgrass Prairie

Abstract Grassland birds have declined more than any other North American habitat-associated bird community. Because most species of grassland birds evolved within heterogeneous landscapes created by the interaction of fire and grazing, traditional rangeland management that promotes homogeneity, including annual dormant-season burning combined with early-intensive grazing, might be partly responsible for these declines, especially in some regions of the Great Plains, USA. Recently, an alternative grassland management practice known as patch-burning has been promoted as a means of restoring heterogeneity to grasslands by mimicking the grazing-fire interaction that once occurred on the prairie before European settlement. From 2003 to 2004, we examined effects of patch-burning and traditional management (annual burning followed by early-intensive grazing) on the reproductive success of dickcissels (Spiza americana) in tallgrass prairie in Oklahoma. We monitored 296 dickcissel nests and found that dickcissel nesting phenology differed between traditional and patch-burned pastures. Specifically, dickcissels tended to initiate their nests later in the traditional pasture. Mean number of eggs laid and fledglings produced were similar between the treatments, but nest densities were higher in traditional pastures. Predation was the predominant cause of nest failure and was higher in traditional pastures than in patch-burned pastures. Brown-headed cowbird (Molothrus ater) parasitism was higher in traditional pastures than in patch-burned pastures. Overall, dickcissel nest success was higher in patch-burned pastures than in traditional pastures. The positive response of dickcissel nest success to patch-burn management provides further evidence that this practice can be a useful tool for grassland bird conservation. By creating a mosaic of different stature vegetation, patch-burn management enhances productivity of grassland bird species by providing a refuge area in the unburned patches that affords dickcissels and other nesting grassland birds some protection from the direct (e.g., trampling) and indirect (e.g., cowbird parasitism and predation) effects of grazing, which are not available under traditional management. Patch-burn management should be encouraged as a conservation strategy for grassland birds throughout the Great Plains.     

ERα is an RNA-binding protein sustaining tumor cell survival and drug resistance

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