Short interfering RNA-mediated knockdown of drosha and pasha in undifferentiated Meloidogyne incognita eggs leads to irregular growth and embryonic lethality

Micro-(mi)RNAs play a pivotal role in the developmental regulation of plants and animals. We reasoned that disruption of normal heterochronic activity in differentiating Meloidogyne incognita eggs may lead to irregular development, lethality and by extension, represent a novel target for parasite control On silencing the nuclear RNase III enzyme drosha, a critical effector of miRNA maturation in animals, we found a significant inhibition of normal development and hatching in short interfering (sORNA-soaked M incognita eggs Developing juveniles presented with highly irregular tissue patterning within the egg, and we found that unlike our previous gene silencing efforts focused on FMRFamide (Phe-Met-Arg-Phe-NH2)-like peptides (FLPs), there was no observable phenotypic recovery following removal of the environmental siRNA. Aberrant phenotypes were exacerbated over time, and drosha knockdown proved embryonically lethal Subsequently, we identified and silenced the drosha cofactor pasha, revealing a comparable inhibition of normal embryonic development within the eggs to that of drosha-silenced eggs, eventually leading to embryonic lethality To further probe the link between normal embryonic development and the M. incognita RNA interference (RNAi) pathway, we attempted to examine the impact of silencing the cytosolic RNase III enzyme dicer. Unexpectedly, we found a substantial up-regulation of dicer transcript abundance, which did not impact on egg differentiation or hatching rates. Silencing of the individual transcripts in hatched J2s was significantly less successful and resulted in temporary phenotypic aberration of the J2s. which recovered within 24 h to normal movement and posture on washing out the siRNA. Soaking the J2s in dicer siRNA resulted in a modest decrease in dicer transcript abundance which had no observable impact on phenotype or behaviour within 48 h of initial exposure to siRNA. We propose that drosha, pasha and their ancillary factors may represent excellent targets for novel nematicides and/or in planta controls aimed at M incognita, and potentially other parasitic nematodes, through disruption of miRNA-directed developmental pathways. In addition, we have identified a putative Mi-en-I transcript which encodes an RNAi-inhibiting siRNA exonuclease We observe a marked up-regulation of MI-en-I transcript abundance in response to exogenously introduced siRNA, and reason that this may impact on the interpretation of RN/NI-based reverse genetic screens in plant parasitic nematodes. (C) 2010 Australian Society for Parasitology Inc. Published by Elsevier Ltd. All rights reserved.

The chemical composition of two supergiants in the dwarf irregular galaxy WLM

The chemical composition of two stars in WLM has been determined from high-quality Ultraviolet-Visual Echelle Spectrograph (UVES) data obtained at the VLT-UT2. The model atmospheres analysis shows that they have the same metallicity, [Fe/H] = - 0.38 +/- 0.20 (+/- 0.29). Reliable magnesium abundances are determined from several lines of two ionization states in both stars resulting in [Mg/Fe] = - 0.24 +/- 0.16 (+/- 0.28). This result suggests that the [alpha(Mg)/Fe] ratio in WLM may be suppressed relative to solar abundances ( also supported by differential abundances relative to similar stars in NGC 6822 and the Small Magellanic Cloud [SMC]). The absolute Mg abundance, [Mg/H] = -0.62, is high relative to what is expected from the nebulae though, where two independent spectroscopic analyses of the H II regions in WLM yield [O/H] = - 0.89. Intriguingly, the oxygen abundance determined from the O I lambda6158 feature in one WLM star is [O/H] = - 0.21 +/- 0.10 (+/- 0.05), corresponding to 5 times higher than the nebular oxygen abundance. This is the first time that a significant difference between stellar and nebular oxygen abundances has been found, and currently, there is no simple explanation for this difference. The two stars are massive supergiants with distances that clearly place them in WLM. They are young ( less than or equal to 10 Myr) and should have a similar composition to the ISM. Additionally, differential abundances suggest that the O/Fe ratio in the WLM star is consistent with similar stars in NGC 6822 and the SMC, galaxies where the average stellar oxygen abundances are in excellent agreement with the nebular results. If the stellar abundances reflect the true composition of WLM, then this galaxy lies well above the metallicity-luminosity relationship for dwarf irregular galaxies. It also suggests that WLM is more chemically evolved than currently interpreted from its color-magnitude diagram. The similarities between the stars in WLM and NGC 6822 suggest that these two galaxies may have had similar star formation histories.

An experimental and numerical investigation into the seismic performance of a multi-storey concentrically braced plan irregular structure

In this investigation, the seismic torsional response of a multi-storey concentrically braced frame (CBF) plan irregular structure is evaluated numerically and experimentally through a series of hybrid tests. CBF structures have become popular in seismic design because they are one of the most efficient types of steel structures to resist earthquake loading. However, their response under plan irregular conditions has received little focus mostly in part
due to their complex behaviour under seismic loading conditions. The majority of research on the seismic response of plan irregular structures is based purely on numerical investigations. This paper provides much needed experimental investigation of the seismic response of a CBF plan irregular structure with the aim of characterising the response of this class of structure. The effectiveness of the Eurocode 8 torsional effects provision as a method of designing for
low levels of mass eccentricity is evaluated. Results indicate that some of the observations made by purely numerical models are valid in that; torsionally stiff structures perform well and the stiff side of the structure is subjected to a greater ductility demand compared to the flexible side of the structure. The Eurocode 8 torsional effects provision is shown to be adequate in terms of ductility and interstorey drift however the structure performs poorly
in terms of floor rotation. Importantly, stiffness eccentricity occurs when the provision is applied to the structure when no mass eccentricity exists and results in a significant increase in floor rotations.

The Enemy of My Enemy is My Friend... The Dynamics of Self-Defense Forces in Irregular War: The Case of the Sons of Iraq

This article assesses the effect that leveraging civilian defense force militias has on the dynamics of violence in civil war. We argue that the delegation of security and combat roles to local civilians shifts the primary targets of insurgent violence toward civilians, in an attempt to deter future defections, and re-establish control over the local population. This argument is assessed through an analysis of the Sunni Awakening and ancillary Sons of Iraq paramilitary program. The results suggest that at least in the Al-Anbar province of Iraq, the utilization of the civilian population in counterinsurgent roles had significant implications for the targets of insurgent violence.