Cowpea aphid performance and behaviour on two resistant cowpea lines

In a series of laboratory and climate chamber tests we compared the growth and behaviour of Aphis craccivora on one susceptible (ICV-1) and two aphid-resistant (ICV-11 and ICV-12) cowpea lines. The aphids' growth rates were much lower on the resistant cowpea lines than on the susceptible one, indicating strong antibiosis. In addition, the aphids invariably settled in higher numbers on the susceptible line than on either of the resistant. Compared to ICV-1, damaged leaves of the resistant line ICV-12 were settled upon to a higher degree than undamaged leaves, and leaf discs from the same line were even less resistant.On resistant lines individual aphids waited a significantly longer time before making their first test probe. Total probing time as well as the time preceding a decision to stay or leave was also longer.These results are discussed in relation to the possible mechanisms involved, and we also consider the effects of previous leaf feeding on the expression of resistance in the field.

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Résumé Au cours d'expériences au laboratoire et en chambres climatisées nous avons comparé la croissance et le comportement de A. craccivora sur une lignée sensible (ICV-1) et deux lignées résistantes (ICV-11 et ICV-12) de V. unguiculata. Les vitesses de croissance des pucerons ont été beaucoup plus lentes sur les lignées résistantes que sur la lignée sensible, ce qui révèle une forte antibiose. De plus, les pucerons atterrissent invariablement en plus grand nombre sur la variété sensible. Par comparaison avec ICV-1, les atterrissages sur lignée résistante ICV-12 étaient plus nombreux sur les feuilles endommagées que sur les feuilles intactes; les disques de feuilles de cette même lignée étaient encore moins résistants.Les pucerons ont séjourné individuellement un temps plus long sur les lignées résistantes avant de faire leur premier sondage. Le temps consacré aux sondages ainsi que le temps précédant de choix entre départ ou maintien sur la feuille étaient plus longs avec les lignées résistantes.Ces résultats ont été discutés en fonction des mécanismes impliqués. Nous avons aussi examiné les effets de la consommation antérieure sur les manifestations de la résistance dans la nature.

     

An ana2/ctp/mud complex regulates spindle orientation in Drosophila neuroblasts

Drosophila neural stem cells, larval brain neuroblasts (NBs), align their mitotic spindles along the apical/basal axis during asymmetric cell division (ACD) to maintain the balance of self-renewal and differentiation. Here, we identified a protein complex composed of the tumor suppressor anastral spindle 2 (Ana2), a dynein light-chain protein Cut up (Ctp), and Mushroom body defect (Mud), which regulates mitotic spindle orientation. We isolated two ana2 alleles that displayed spindle misorientation and NB overgrowth phenotypes in larval brains. The centriolar protein Ana2 anchors Ctp to centrioles during ACD. The centriolar localization of Ctp is important for spindle orientation. Ana2 and Ctp localize Mud to the centrosomes and cell cortex and facilitate/maintain the association of Mud with Pins at the apical cortex. Our findings reveal that the centrosomal proteins Ana2 and Ctp regulate Mud function to?orient the mitotic spindle during NB asymmetric division.     

Liposomal encapsulation of glucocorticoids alters their mode of action in the treatment of experimental autoimmune encephalomyelitis

Glucocorticoids (GCs) are widely used to treat acute relapses of multiple sclerosis (MS). In this study, we demonstrate that liposomal encapsulation augments the therapeutic potency of GCs as they ameliorate experimental autoimmune encephalomyelitis (EAE) to the same extent as free GC, but at strongly reduced dosage and application frequency. Importantly, this is accompanied by an altered mode of action. Unlike free GCs, which mainly target T lymphocytes during EAE therapy, liposomal GCs only marginally affect T cell apoptosis and function. In contrast, liposomal GCs efficiently repress proinflammatory macrophage functions and upregulate anti-inflammatory genes associated with the alternatively activated M2 phenotype. The GC receptor (GR) per se is indispensable for the therapeutic efficacy of liposomal GC. In contrast to free GCs, however, the individual deletion of the GR either in T cells or myeloid cells has little effect on the efficacy of liposomal GCs in the treatment of EAE. Only the combined deletion of the GR in both cellular compartments markedly compromises the therapeutic effect of liposomal GCs on disease progression. In conclusion, encapsulation of GC does not only enhance their efficacy in the treatment of EAE but also alters their target cell specificity and their mode of action compared with free GCs.     

The Botrytis cinerea phytotoxin botcinic acid requires two polyketide synthases for production and has a redundant role in virulence with botrydial

The grey mould fungus Botrytis cinerea produces two major phytotoxins, the sesquiterpene botrydial, for which the biosynthesis gene cluster has been characterized previously, and the polyketide botcinic acid. We have identified two polyketide synthase (PKS) encoding genes, BcPKS6 and BcPKS9, that are up-regulated during tomato leaf infection. Gene inactivation and analysis of the secondary metabolite spectra of several independent mutants demonstrated that both BcPKS6 and BcPKS9 are key enzymes for botcinic acid biosynthesis. We showed that BcPKS6 and BcPKS9 genes, renamed BcBOA6 and BcBO9 (for B. cinerea botcinic acid biosynthesis), are located at different genomic loci, each being adjacent to other putative botcinic acid biosynthetic genes, named BcBOA1 to BcBOA17. Putative orthologues of BcBOA genes are present in the closely related fungus Sclerotinia sclerotiorum, but the cluster organization is not conserved between the two species. As for the botrydial biosynthesis genes, the expression of BcBOA genes is co-regulated by the Gα subunit BCG1 during both in vitro and in planta growth. The loss of botcinic acid production does not affect virulence on bean and tomato leaves. However, double mutants that do not produce botcinic acid or botrydial (bcpks6Δbcbot2Δ) exhibit markedly reduced virulence. Hence, a redundant role of botrydial and botcinic acid in the virulence of B. cinerea has been demonstrated.     

Three groups of interneurons account for nearly 100% of neocortical GABAergic neurons

An understanding of the diversity of cortical GABAergic interneurons is critical to understand the function of the cerebral cortex. Recent data suggest that neurons expressing three markers, the Ca2+-binding protein parvalbumin (PV), the neuropeptide somatostatin (SST), and the ionotropic serotonin receptor 5HT3a (5HT3aR) account for nearly 100% of neocortical interneurons. Interneurons expressing each of these markers have a different embryological origin. Each group includes several types of interneurons that differ in morphological and electrophysiological properties and likely have different functions in the cortical circuit. The PV group accounts for ～40% of GABAergic neurons and includes fast spiking basket cells and chandelier cells. The SST group, which represents ～30% of GABAergic neurons, includes the Martinotti cells and a set of neurons that specifically target layerIV. The 5HT3aR group, which also accounts for ～30% of the total interneuronal population, is heterogeneous and includes all of the neurons that express the neuropeptide VIP, as well as an equally numerous subgroup of neurons that do not express VIP and includes neurogliaform cells. The universal modulation of these neurons by serotonin and acetylcholine via ionotropic receptors suggests that they might be involved in shaping cortical circuits during specific brain states and behavioral contexts.     

Structure of apolipoprotein A-I N terminus on nascent high density lipoproteins

Apolipoprotein A-I (apoA-I) is the major protein component of high density lipoproteins (HDL) and a critical element of cholesterol metabolism. To better elucidate the role of the apoA-I structure-function in cholesterol metabolism, the conformation of the apoA-I N terminus (residues 6-98) on nascent HDL was examined by electron paramagnetic resonance (EPR) spectroscopic analysis. A series of 93 apoA-I variants bearing single nitroxide spin label at positions 6-98 was reconstituted onto 9.6-nm HDL particles (rHDL). These particles were subjected to EPR spectral analysis, measuring regional flexibility and side chain solvent accessibility. Secondary structure was elucidated from side-chain mobility and molecular accessibility, wherein two major α-helical domains were localized to residues 6-34 and 50-98. We identified an unstructured segment (residues 35-39) and a β-strand (residues 40-49) between the two helices. Residues 14, 19, 34, 37, 41, and 58 were examined by EPR on 7.8, 8.4, and 9.6 nm rHDL to assess the effect of particle size on the N-terminal structure. Residues 14, 19, and 58 showed no significant rHDL size-dependent spectral or accessibility differences, whereas residues 34, 37, and 41 displayed moderate spectral changes along with substantial rHDL size-dependent differences in molecular accessibility. We have elucidated the secondary structure of the N-terminal domain of apoA-I on 9.6 nm rHDL (residues 6-98) and identified residues in this region that are affected by particle size. We conclude that the inter-helical segment (residues 35-49) plays a role in the adaptation of apoA-I to the particle size of HDL.     

Machupo virus glycoprotein determinants for human transferrin receptor 1 binding and cell entry

Machupo virus (MACV) is a highly pathogenic New World arenavirus that causes hemorrhagic fever in humans. MACV, as well as other pathogenic New World arenaviruses, enter cells after their GP1 attachment glycoprotein binds to their cellular receptor, transferrin receptor 1 (TfR1). TfR1 residues essential for this interaction have been described, and a co-crystal of MACV GP1 bound to TfR1 suggests GP1 residues important for this association. We created MACV GP1 variants and tested their effect on TfR1 binding and virus entry to evaluate the functional significance of some of these and additional residues in human and simian cells. We found residues R111, D123, Y122, and F226 to be essential, D155, and P160 important, and D114, S116, D140, and K169 expendable for the GP1-TfR1 interaction and MACV entry. Several MACV GP1 residues that are critical for the interaction with TfR1 are conserved among other New World arenaviruses, indicating a common basis of receptor interaction. Our findings also open avenues for the rational development of viral entry inhibitors.     

Comparison of two oxygen delivery systems for safe sedation and spinal anesthesia in sheep

Proper oxygenation is critical to prevent hypoxia and myocardial ischemia in animals during pharmacological sedation. The authors compared the efficacy of two oxygen delivery masks during sedation and spinal anesthesia for knee surgery in sheep.     

Anaphase specific auto-cleavage of separase

Sister-chromatid separation is triggered by a specific proteolytic cleavage of chromosomal cohesins catalyzed by the endopeptidase separase. Prior to anaphase, separase is inhibited independently by affinity binding to securin and by specific inhibitory phosphorylation. Here we show that separase itself is also subjected to proteolytic cleavages at three adjacent sites. The cleavages are auto-catalyzed and occur specifically at anaphase coincident with separase activation. The cleaved fragments remain associated with each other and are catalytically active. Mapping of the cleavage sites reveals that all three sites are conserved in vertebrates underlining a significant function for this regulation.