Perturbing Dynamin Reveals Potent Effects on the Drosophila Circadian Clock

BACKGROUND: Transcriptional feedback loops are central to circadian clock function. However, the role of neural activity and membrane events in molecular rhythms in the fruit fly Drosophila is unclear. To address this question, we expressed a temperature-sensitive, dominant negative allele of the fly homolog of dynamin called shibire(ts1) (shi(ts1)), an active component in membrane vesicle scission. PRINCIPAL FINDINGS: Broad expression in clock cells resulted in unexpectedly long, robust periods (>28 hours) comparable to perturbation of core clock components, suggesting an unappreciated role of membrane dynamics in setting period. Expression in the pacemaker lateral ventral neurons (LNv) was necessary and sufficient for this effect. Manipulation of other endocytic components exacerbated shi(ts1)'s behavioral effects, suggesting its mechanism is specific to endocytic regulation. PKA overexpression rescued period effects suggesting shi(ts1) may downregulate PKA pathways. Levels of the clock component PERIOD were reduced in the shi(ts1)-expressing pacemaker small LNv of flies held at a fully restrictive temperature (29 degrees C). Less restrictive conditions (25 degrees C) delayed cycling proportional to observed behavioral changes. Levels of the neuropeptide PIGMENT-DISPERSING FACTOR (PDF), the only known LNv neurotransmitter, were also reduced, but PERIOD cycling was still delayed in flies lacking PDF, implicating a PDF-independent process. Further, shi(ts1) expression in the eye also results in reduced PER protein and per and vri transcript levels, suggesting that shibire-dependent signaling extends to peripheral clocks. The level of nuclear CLK, transcriptional activator of many core clock genes, is also reduced in shi(ts1) flies, and Clk overexpression suppresses the period-altering effects of shi(ts1). CONCLUSIONS: We propose that membrane protein turnover through endocytic regulation of PKA pathways modulates the core clock by altering CLK levels and/or activity. These results suggest an important role for membrane scission in setting circadian period

Skeletal Morphology of Opius dissitus and Biosteres carbonarius (Hymenoptera: Braconidae), with a Discussion of Terminology

The Braconidae, a family of parasitic wasps, constitute a major taxonomic challenge with an estimated diversity of 40,000 to 120,000 species worldwide, only 18,000 of which have been described to date. The skeletal morphology of braconids is still not adequately understood and the terminology is partly idiosyncratic, despite the fact that anatomical features form the basis for most taxonomic work on the group. To help address this problem, we describe the external skeletal morphology of Opius dissitus Muesebeck 1963 and Biosteres carbonarius Nees 1834, two diverse representatives of one of the least known and most diverse braconid subfamilies, the Opiinae. We review the terminology used to describe skeletal features in the Ichneumonoidea in general and the Opiinae in particular, and identify a list of recommend terms, which are linked to the online Hymenoptera Anatomy Ontology. The morphology of the studied species is illustrated with SEM-micrographs, photos and line drawings. Based on the examined species, we discuss intraspecific and interspecific morphological variation in the Opiinae and point out character complexes that merit further study

Potential exposure of a classical biological control agent of the soybean aphid, Aphis glycines, on non-target aphids in North America

In summer 2007, the Asian parasitoid Binodoxys communis (Hymenoptera: Braconidae) was released in North America for control of the exotic soybean aphid, Aphis glycines (Hemiptera: Aphididae). Despite its comparatively narrow host range, releases of B. communis may still constitute a risk to native aphid species. To estimate the risk of exposure of non-target aphids to B. communis, we merged assessments of temporal co-occurrence with projections of spatial overlap between B. communis and three native aphid species, and in-field measurements of the incidence of ecological filters that may protect these aphids from parasitism. Temporal co-occurrence was assessed between A. glycines and native aphids (Aphis asclepiadis, Aphis oestlundi, and Aphis monardae) at four different locations in Minnesota, USA. The degree of temporal overlap depended greatly on location and aphid species, ranging between 0 and 100%. All of the native aphids were tended by multiple species of ants, with overall ant-attendance ranging from 26.1 to 89.6%. During temporal overlap with A. glycines, 53 ± 11% of A. monardae colonies were partly found in flower heads of their host plant, with flowers acting as a physical refuge for this aphid. The extent of geographic overlap between B. communis and native aphids based upon Climex modeling was 17 28% for A. monardae, 13 22% for A. oestlundi, 46 55% for A. asclepiadis and 12 24% for the A. asclepiadis species complex. The estimated overall probability of potential exposure of B. communis on native aphids was relatively low (P = 0.115) for A. oestlundi and high (P = 0.550) for A. asclepiades. Physical and ant-mediated refuges considerably lowered probability of population-level impact on A. monardae, and could lead to substantial reduction of exposure for the other native aphids. These findings are used to make broader statements regarding the ecological safety of current B. communis releases and their potential impact on native aphid species in North America