No abstract

The brown dog tick, Rhipicephalus sanguineus (Latrielle) sensu lato, is an important ectoparasite of dogs and occasionally humans, capable of transmitting several pathogens, such as Rickettsia and Ehrlichia, which are of veterinary and medical importance. The brown dog tick is distributed worldwide and has an affinity for human habitations in much of its range. In some populations, lack of integrated pest management plans and overuse of pyrethroid pesticides and other sodium channel inhibitors has resulted in high levels of resistance to permethrin. Recently, a highly conserved region of the R. sanguineus sodium channel was sequenced, indicating that a single nucleotide polymorphism of thymine to cytosine on domain III segment VI of the sodium channel could confer resistance. A molecular assay targeting a point mutation in the sodium channel was developed and optimized to separate ticks expressing permethrin resistance from those from a susceptible colony. Thereafter, multiple field-collected phenotypically permethrin-resistant populations were evaluated using this molecular assay to determine genotype. As confirmed by DNA sequencing, a point mutation was present at a high rate in phenotypically resistant tick populations that was not present in the susceptible strain. These data suggest an additional permethrin resistance mechanism to metabolic resistance, which has been reported for this tick species, and confirm its association with phenotypic resistance. The results of this study further emphasize the need to preserve acaricide chemistry through rotation of active ingredients used to control ectoparasites.

BackgroundTick parasitism is a major impediment for cattle production in many parts of the world. The southern cattle tick, Rhipicephalus (Boophilus) microplus, is an obligate hematophagous parasite of domestic and wild animals that serves as vector of infectious agents lethal to cattle. Tick saliva contains molecules evolved to modulate host innate and adaptive immune responses which facilitates blood feeding and pathogen transmission. Tick feeding promotes CD4 T cell polarization to a Th2 profile usually accompanied by down-regulation of Th1 cytokines through as yet undefined mechanisms. Co-stimulatory molecules on antigen presenting cells are central to development of T cell responses including Th1 and Th2 responses. Tick induced changes to antigen presenting cell signal transduction pathways are largely unknown. Here we document the ability of R. microplus salivary gland extracts (SGE) to effect differential CD86 expression.ResultsWe examined changes in co-stimulatory molecule expression in murine RAW 264.7 cells in response to R. microplus SGE exposure in the presence of the toll-like receptor 4 (TLR4) ligand, LPS. After 24 hrs, CD86, but not CD80, was preferentially up-regulated on mouse macrophage RAW 264.7 cells when treated with SGE and then LPS, but not SGE alone. CD80 and CD40 expression was increased with LPS, but the addition of SGE did not alter expression. Higher concentrations of SGE were less effective at increasing CD86 RNA expression. The addition of mitogen or extracellular kinase (MEK) inhibitor, PD98059, significantly reduced the ability for SGE to induce CD86 expression, indicating activation of MEK is necessary for SGE induced up-regulation.ConclusionsMolecules in SGE of R. microplus have a concentration-dependent effect on differential up-regulation of CD86 in a macrophage cell line activated by the TLR4 ligand, LPS. This CD86 up-regulation is at least partially dependent on the ERK1/2 pathway and may serve to promote Th2 polarization of the immune response.

The giant reed, Arundo donax, is a perennial grass species that has become an invasive plant in many countries. Expansive stands of A. donax have significant negative impacts on available water resources and efforts are underway to identify biological control agents against this species. The giant reed grows under adverse environmental conditions, displaying insensitivity to drought stress, flooding, heavy metals, salinity and herbaceous competition, thus hampering control programs. To establish a foundational molecular dataset, we used an llumina Hi-Seq protocol to sequence the transcriptome of actively growing shoots from an invasive genotype collected along the Rio Grande River, bordering Texas and Mexico. We report the assembly of 27,491 high confidence transcripts (≥200 bp) with at least 70% coverage of known genes in other Poaceae species. Of these 13,080 (47.58%), 6165 (22.43%) and 8246 (30.0%) transcripts have sequence similarity to known, domain-containing and conserved hypothetical proteins, respectively. We also report 75,590 low confidence transcripts supported by both trans-ABBySS and Velvet-Oases de novo assembly pipelines. Within the low confidence subset of transcripts we identified partial hits to known (19,021; 25.16%), domain-containing (7093; 9.38%) and conserved hypothetical (16,647; 22.02%) proteins. Additionally 32,829 (43.43%) transcripts encode putative hypothetical proteins unique to A. donax. Functional annotation resulted in 5,550 and 6,070 transcripts with assigned Gene Ontology and KEGG pathway information, respectively. The most abundant KEGG pathways are spliceosome, ribosome, ubiquitin mediated proteolysis, plant–pathogen interaction, RNA degradation and oxidative phosphorylation metabolic pathway. Furthermore, we also found 12, 9, and 4 transcripts annotated as stress-related, heat stress, and water stress proteins, respectively. We envisage that these resources will promote and facilitate studies of the abiotic stress capabilities of this exotic plant species, which facilitates its invasive capacity.