Resistance to pathogens in terpene down-regulated orange fruits inversely correlates with the accumulation of D-limonene in peel oil glands

Volatile organic compounds (VOCs) are secondary metabolites acting as a language for the communication of plants with the environment. In orange fruits, the monoterpene D-limonene accumulates at very high levels in oil glands from the peel. Drastic down-regulation of D-limonene synthase gene expression in the peel of transgenic oranges harboring a D-limonene synthase transgene in antisense (AS) configuration altered the monoterpene profile in oil glands, mainly resulting in reduced accumulation of D-limonene. This led to fruit resistance against Penicillium digitatum (Pd), Xanthomonas citri subsp. citri (Xcc) and other specialized pathogens. Here, we analyze resistance to pathogens in independent AS and empty vector (EV) lines, which have low, medium or high D-limonene concentrations and show that the level of resistance is inversely related to the accumulation of D-limonene in orange peels, thus explaining the need of high D-limonene accumulation in mature oranges in nature for the efficient attraction of specialized microorganism frugivores.     

New Type of Papillomavirus and Novel Circular Single Stranded DNA Virus Discovered in Urban Rattus norvegicus Using Circular DNA Enrichment and Metagenomics

Rattus norvegicus (R. norvegicus) are ubiquitous and their presence has several effects on the human populations in our urban areas on a global scale. Both historically and presently, this close interaction has facilitated the dissemination of many pathogens to humans, making screening for potentially zoonotic and emerging viruses in rats highly relevant. We have investigated faecal samples from R. norvegicus collected from urban areas using a protocol based on metagenomic enrichment of circular DNA genomes and subsequent sequencing. We found a new type of papillomavirus, with a L1 region 82% identical to that of the known R. norvegicus Papillomavirus 2. Additionally, we found 20 different circular replication associated protein (Rep)-encoding single stranded DNA (CRESS-DNA) virus-like genomes, one of which has homology to the replication-associated gene of Beak and feather disease virus. Papillomaviruses are a group of viruses known for their carcinogenic potential, and although they are known to infect several different vertebrates, they are mainly studied and characterised in humans. CRESS-DNA viruses are found in many different environments and tissue types. Both papillomaviruses and CRESS-DNA viruses are known to have pathogenic potential and screening for novel and known viruses in R. norvegicus could help identify viruses with pathogenic potential.     

Insecticidal and Repellent Activity of Siparuna guianensis Aubl. (Negramina) against Aedes aegypti and Culex quinquefasciatus

This study investigated the toxic effects of essential oils isolated from Siparuna guianensis against Aedes aegypti, Culex quinquefasciatus (eggs, larvae, pupae, and adult) and Aedes albopictus (C6/36) cells. The oviposition-deterring activity, egg viability, and repellence activity in the presence of different essential oils concentrations were determined. The essential oils showed high toxicity to all developmental stages of A. aegypti and C. quinquefasciatus. Furthermore, the oils also showed high repellent activity towards the adult stage of mosquitoes (0.025 to 0.550 μg/cm2 skin conferred 100% repellence up to 120 min) and in contact with cultured insect cells (C6/36) induced death possibly by necrosis. The results presented in this work show the potential of S. guianensis essential oils for the development of an alternative and effective method for the natural control of mosquitoes in homes and urban areas.     

Efficient expression of a Trypanosoma cruzi antigen in Escherichia coli and Staphylococcus aureus and its rapid purification

A Trypanosoma cruzi antigen gene was closed into a fusion vector based on the IgG binding domain of Staphylococcus aureus protein A. This vector transformed into Escherichia coli or Staphylococcus aureus and produced about 12 mg fusion protein/l culture. In E. coli, the product remained intracellular while in S. aureus it was excreted into the growth medium. The hybrid protein was purified by IgG Sepharose affinity chromatography. The presence of a cleavage site for enterokinase between protein A and the T. cruzi antigen in the fusion protein allowed the efficient release of the unfused antigen by enzymatic treatment. Further affinity chromatography through IgG Sepharose resulted in the production of the T. cruzi antigen free of protein A.The authors are with the Department of Molecular Genetics, BioSidus S.A., Constitución 4234, 1254, Buenos Aires, Argentina.     

High T cell epitope sharing between two HLA-B27 subtypes (B*2705 and B*2709) differentially associated to ankylosing spondylitis.

HLA-B*2705 is strongly associated with ankylosing spondylitis (AS) and reactive arthritis. In contrast, B*2709 has been reported to be more weakly or not associated to AS. These two molecules differ by a single amino acid change: aspartic acid in B*2705 or histidine in B*2709 at position 116. In this study, we analyzed the degree of T cell epitope sharing between the two subtypes. Ten allospecific T cell clones raised against B*2705, 10 clones raised against B*2703 but cross-reactive with B*2705, and 10 clones raised against B*2709 were examined for their capacity to lyse B*2705 and B*2709 target cells. The anti-B*2705 and anti-B*2703 CTL were peptide dependent as demonstrated by their failure to lyse TAP-deficient B*2705-T2 transfectant cells. Eight of the anti-B*2705 and five of the anti-B*2703 CTL clones lysed B*2709 targets. The degree of cross-reaction between B*2705 and B*2709 was donor dependent. In addition, the effect of the B*2709 mutation (D116H) on allorecognition was smaller than the effect of the other naturally occurring subtype change at this position, D116Y. These results demonstrate that B*2705 and B*2709 are the antigenically closest HLA-B27 subtypes. Because allospecific T cell recognition is peptide dependent, our results imply that the B*2705- and B*2709-bound peptide repertoires are largely overlapping. Thus, to the extent to which linkage of HLA-B27 with AS is related to the peptide-presenting properties of this molecule, our results would imply that peptides within a relatively small fraction of the HLA-B27-bound peptide repertoire influence susceptibility to this disease.     

Relationship of different feeding groups of true bugs (Hemiptera: Heteroptera) with habitat and landscape features in Pannonic salt grasslands

Eastern European grasslands are still inhabited by a rich arthropod fauna, but the drivers and mechanisms influencing their communities have to be understood to ensure their future survival. Heteroptera communities were studied in 20 plot-pairs in Pannonic salt steppe–salt marsh mosaics in Hungary. The effects of vegetation characteristics, landscape diversity and the proportion of surrounding grasslands on the composition, species richness and abundance of different feeding groups of true bugs (carnivores, specialist and generalist herbivores) were examined using ordinations and mixed-effect models. We found distinct herbivorous assemblages corresponding to microtopography-driven differences in water regime and vegetation between steppe and marsh plots, but this pattern was less pronounced in carnivorous assemblages. A higher species richness of true bugs was found in the more diverse steppe vegetation than in the salt marsh vegetation, while the abundance pattern of true bugs was opposite. Landscape diversity had a positive effect on the species richness and abundance of generalist herbivores and carnivores. Our results suggested that generalist herbivores and carnivores appear to drive diversity patterns in the local landscape due to their high dispersal abilities and the broader range of resources they can utilize. Specialist herbivores strongly influence the local insect biomass in relation to the distribution and density of their host plants. The present study highlights the importance of both habitat and landscape diversity for local insect diversity in Pannonic salt grasslands and suggests that the main threats for arthropod diversity are those processes and activities that homogenize these areas.