X-ray doses to safely release the parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae) reared on Anastrepha fraterculus larvae (Diptera: Tephritidae)

Diachasmimorpha longicaudata is a koinobiont larval parasitoid that is currently used to control fruit flies of the genera Anastrepha, Ceratitis and Bactrocera. In the rearing process, a fraction of the host larvae that are exposed to parasitoids escape from parasitism and develop into viable and fertile flies. This creates the need to eliminate emerging flies before the parasitoids are shipped for release, increasing costs due to additional handling steps. Exposure of fly eggs or larvae to gamma-irradiation before they are parasitised has been used to reproductively sterilise hosts, or even inhibit their emergence. Our aim was to determine whether X-ray radiation applied to Anastrepha fraterculus third instar larvae before they are exposed to parasitoids, inhibits fly emergence in non-parasitised larvae without affecting the performance of the parasitoids that emerge from parasitised larvae. Three X-ray doses: 6250.2 R, 8333.6 R and 10417 R (equivalent to 60, 80 and 100 Gy, respectively) and one γ-ray dose (100 Gy) were tested. Fly emergence decreased with increasing doses of radiation, showing null values for the higher X-ray dose and the dose of 100 Gy. Irradiation showed either no impact or a positive effect on parasitism rate and fecundity. Sex rate was biased towards females in almost every dose. We conclude that the two types of radiation evaluated here were equally effective in suppressing fly emergence with no detrimental effects on the biological quality of the produced parasitoids. X-rays offer an alternative method of irradiation than the conventional radiation source, i.e. γ-rays. These results represent a significant improvement in the development of a biological control programme against A. fraterculus.     

THO2, a core member of the THO/TREX complex,is required for microRNA production in Arabidopsis

The THO/TREX complex mediates transport of nascent mRNAs from the nucleus towards the cytoplasm in animals, and has a role in small interfering RNA‐dependent processes in plants. Here we describe five mutant alleles of Arabidopsis thaliana THO2, which encodes a core subunit of the plant THO/TREX complex. tho2 mutants present strong developmental defects resembling those in plants compromised in microRNA (miRNA) activity. In agreement, not only were the levels of siRNAs reduced in tho2 mutants, but also those of mature miRNAs. As a consequence, a feedback mechanism is triggered, increasing the amount of miRNA precursors, and finally causing accumulation of miRNA‐targeted mRNAs. Yeast two‐hybrid experiments and confocal microscopy showed that THO2 does not appear to interact with any of the known miRNA biogenesis components, but rather with the splicing machinery, implying an indirect role of THO2 in small RNA biogenesis. Using an RNA immunoprecipitation approach, we found that THO2 interacts with miRNA precursors, and that tho2 mutants fail to recruit such precursors into the miRNA‐processing complex, explaining the reduction in miRNA production in this mutant background. We also detected alterations in the splicing pattern of genes encoding serine/arginine‐rich proteins in tho2 mutants, supporting a previously unappreciated role of the THO/TREX complex in alternative splicing.     

Evolution and Conservation of Central African Biodiversity: Priorities for Future Research and Education in the Congo Basin and Gulf of Guinea

The tropical forests of the Congo Basin and Gulf of Guinea harbor some of the greatest terrestrial and aquatic biological diversity in the world. However, our knowledge of the rich biological diversity of this region and the evolutionary processes that have shaped it remains limited, as is our understanding of the capacity for species to adapt or otherwise respond to current and projected environmental change. In this regard, research efforts are needed to increase current scientific knowledge of this region's biodiversity, identify the drivers of past diversification, evaluate the potential for species to adapt to environmental change and identify key populations for future conservation. Moreover, when evolutionary research is combined with ongoing environmental monitoring efforts, it can also provide an important set of tools for assessing and mitigating the impacts of development activities. Building on a set of recommendations developed at an international workshop held in Gabon in 2011, we highlight major areas for future evolutionary research that could be directly tied to conservation priorities for the region. These research priorities are centered around five disciplinary themes: (1) documenting and discovering biodiversity; (2) identifying drivers of evolutionary diversification; (3) monitoring environmental change; (4) understanding community and ecosystem level processes; (5) investigating the ecology and epidemiology of disease from an evolutionary perspective (evolutionary epidemiology). Furthermore, we also provide an overview of the needs and priorities for biodiversity education and training in Central Africa.     

Evolutionary change in testes tissue composition among experimental populations of house mice

Theory assumes that postcopulatory sexual selection favors increased investment in testes size because greater numbers of sperm within the ejaculate increase the chance of success in sperm competition, and larger testes are able to produce more sperm. However, changes in the organization of the testes tissue may also affect sperm production rates. Indeed, recent comparative analyses suggest that sperm competition selects for greater proportions of sperm‐producing tissue within the testes. Here, we explicitly test this hypothesis using the powerful technique of experimental evolution. We allowed house mice (Mus domesticus) to evolve via monogamy or polygamy in six replicate populations across 24 generations. We then used histology and image analysis to quantify the proportion of sperm‐producing tissue (seminiferous tubules) within the testes of males. Our results show that males that had evolved with sperm competition had testes with a higher proportion of seminiferous tubules compared with males that had evolved under monogamy. Previously, it had been shown that males from the polygamous populations produced greater numbers of sperm in the absence of changes in testes size. We thus provide evidence that sperm competition selects for an increase in the density of sperm‐producing tissue, and consequently increased testicular efficiency.     

Guanine Nucleotide Exchange Factor αPIX Leads to Activation of the Rac 1 GTPase/Glycogen Phosphorylase Pathway in Interleukin (IL)-2-stimulated T Cells

Recently, we have reported that the active form of Rac 1 GTPase binds to the glycogen phosphorylase muscle isoform (PYGM) and modulates its enzymatic activity leading to T cell proliferation. In the lymphoid system, Rac 1 and in general other small GTPases of the Rho family participate in the signaling cascades that are activated after engagement of the T cell antigen receptor. However, little is known about the IL-2-dependent Rac 1 activator molecules. For the first time, a signaling pathway leading to the activation of Rac 1/PYGM in response to IL-2-stimulated T cell proliferation is described. More specifically, αPIX, a known guanine nucleotide exchange factor for the small GTPases of the Rho family, preferentially Rac 1, mediates PYGM activation in Kit 225 T cells stimulated with IL-2. Using directed mutagenesis, phosphorylation of αPIX Rho-GEF serines 225 and 488 is required for activation of the Rac 1/PYGM pathway. IL-2-stimulated serine phosphorylation was corroborated in Kit 225 T cells cultures. A parallel pharmacological and genetic approach identified PKCθ as the serine/threonine kinase responsible for αPIX serine phosphorylation. The phosphorylated state of αPIX was required to activate first Rac 1 and subsequently PYGM. These results demonstrate that the IL-2 receptor activation, among other early events, leads to activation of PKCθ. To activate Rac 1 and consequently PYGM, PKCθ phosphorylates αPIX in T cells. The biological significance of this PKCθ/αPIX/Rac 1 GTPase/PYGM signaling pathway seems to be the control of different cellular responses such as migration and proliferation.