Salivary enzymes are injected into xylem by the glassy-winged sharpshooter, a vector of Xylella fastidiosa

A few phytophagous hemipteran species such as the glassy-winged sharpshooter, Homalodisca vitripennis, (Germar), subsist entirely on xylem fluid. Although poorly understood, aspects of the insect's salivary physiology may facilitate both xylem-feeding and transmission of plant pathogens. Xylella fastidiosa is a xylem-limited bacterium that causes Pierce's disease of grape and other scorch diseases in many important crops. X. fastidiosa colonizes the anterior foregut (precibarium and cibarium) of H. vitripennis and other xylem-feeding vectors. Bacteria form a dense biofilm anchored in part by an exopolysaccharide (EPS) matrix that is reported to have a β-1,4-glucan backbone. Recently published evidence supports the following, salivation-egestion hypothesis for the inoculation of X. fastidiosa during vector feeding. The insect secretes saliva into the plant and then rapidly takes up a mixture of saliva and plant constituents. During turbulent fluid movements in the precibarium, the bacteria may become mechanically and enzymatically dislodged; the mixture is then egested back out through the stylets into plant cells, possibly including xylem vessels. The present study found that proteins extracted from dissected H. vitripennis salivary glands contain several enzyme activities capable of hydrolyzing glycosidic linkages in polysaccharides such as those found in EPS and plant cell walls, based on current information about the structures of those polysaccharides. One of these enzymes, a β-1,4-endoglucanase (EGase) was enriched in the salivary gland protein extract by subjecting the extract to a few, simple purification steps. The EGase-enriched extract was then used to generate a polyclonal antiserum that was used for immunohistochemical imaging of enzymes in sharpshooter salivary sheaths in grape. Results showed that enzyme-containing gelling saliva is injected into xylem vessels during sharpshooter feeding, in one case being carried by the transpiration stream away from the injection site. Thus, the present study provides support for the salivation-egestion hypothesis.     

Radiating on oceanic islands: patterns and processes of speciation in the land snail genus Theba (Risso 1826)

Island radiations have played a major role in shaping our current understanding of allopatric, sympatric and parapatric speciation. However, the fact that species divergence correlates with island size emphasizes the importance of geographic isolation (allopatry) in speciation. Based on molecular and morphological data, we investigated the diversification of the land snail genus Theba on the two Canary Islands of Lanzarote and Fuerteventura. Due to the geological history of both islands, this study system provides ideal conditions to investigate the interplay of biogeography, dispersal ability and differentiation in generating species diversity. Our analyses demonstrated extensive cryptic diversification of Theba on these islands, probably driven mainly by non-adaptive allopatric differentiation and secondary gene flow. In a few cases, we observed a complete absence of gene flow among sympatrically distributed forms suggesting an advanced stage of speciation. On the Jandía peninsula genome scans suggested genotype-environment associations and potentially adaptive diversification of two closely related Theba species to different ecological environments. We found support for the idea that genetic differentiation was enhanced by divergent selection in different environments. The diversification of Theba on both islands is therefore best explained by a mixture of non-adaptive and adaptive speciation, promoted by ecological and geomorphological factors.     

Temperature-triggered self-assembly of elastin-like block co-recombinamers:the controlled formation of micelles and vesicles in an aqueous medium

The possibility of obtaining different self-assembled nanostructures in reversible systems based on elastin-like block corecombinamers is explored in this work. The results obtained show how an evolution from a more common micellar structure to a hollow vesicle can be attained simply by changing the block arrangements and lengths, even when other molecular properties, such as molecular weight or mean polarity, remain essentially unchanged. This work sheds light on the possibility of obtaining hollow nano-objects, based on elastin-like recombinamers, which can assemble and disassemble in response to a change in their surroundings. This kind of system can be an example of how high precision in the genetic production of synthetic macro-molecules can be used, on an exclusive basis, to control the shape and size of their derived nano-objects.     

Host location and suitability of the armyworm larvae of Mythimna unipuncta for the tachinid parasitoid Exorista larvarum

This work evaluates the efficiency of Exorista larvarum (L.) (Diptera: Tachinidae) in localizing and parasitizing the larvae of the noctuid moth Mythimna unipuncta (Haworth) (Lepidoptera: Noctuidae) in laboratory conditions, in a wind tunnel and in PVC cages. The most important cue in host localization by E. larvarum females was host-induced plant volatiles. Visual cues, natural maize volatiles and artificially damaged plants were less efficient for host localization. Mortality in M. unipuncta larvae on which E. larvarum females laid eggs was high. This finding indicates that E. larvarum could effectively contribute to lowering the population size of M. unipuncta, even if only few parasitoids successfully complete their development in the host. Further studies with other possible hosts must be done to apply E. larvarum successfully against M. unipuncta larvae in maize fields.     

Development of pyridine-containing macrocyclic copper(II) complexes: potential role in the redox modulation of oxaliplatin toxicity in human breast cells

The unique redox and catalytic chemistry of Cu has justified the development of novel Cu complexes for different therapeutic uses including cancer therapy. In this work, four pyridine-containing aza-macrocyclic copper(II) complexes were prepared (CuL1-CuL4) varying in ring size and/or substituents and their superoxide scavenging activity evaluated. CuL3, the most active superoxide scavenger, was further studied as a modulator of the cytotoxicity of oxaliplatin in epithelial breast MCF10A cells and in MCF7 breast cancer cells. Our results show that CuL3 enhances the therapeutic window of oxaliplatin, by both protecting non-tumour cells and increasing its cytotoxic effect in breast carcinoma cells. CuL3 is thus a promising complex to be further studied and to be used as a lead compound for the optimization of novel chemotherapy sensitizers.