Interaction of plant essential oil terpenoids with the southern cattle tick tyramine receptor: A potential biopesticide target

Abstract

a b s t r a c tAn outbreak of the southern cattle tick, Rhipicephalus (Boophilus) microplus, (Canestrini), in the United States would have devastating consequences on the cattle industry. Tick populations have developed resistance to current acaricides, highlighting the need to identify new biochemical targets along with new chemistry. Furthermore, acaricide resistance could further hamper control of tick populations during an outbreak. Botanically-based compounds may provide a safe alternative for efficacious control of the southern cattle tick. We have developed a heterologous expression system that stably expresses the cattle tick's tyramine receptor with a G-protein chimera, producing a system that is amenable to high-throughput screening. Screening an in-house terpenoid library, at two screening concentrations (10 mM and 100 mM), has identified four terpenoids (piperonyl alcohol, 1,4-cineole, carvacrol and isoeugenol) that we believe are positive modulators of the southern cattle tick's tyramine receptor.

Plant essential oils synergize various pyrethroid insecticides and antagonize malathion in Aedes aegypti

“…This in turn could lead to the higher percentage mortality and account for the synergism seen in this study. Multiple other studies have suggested that plant essential oils enhance the toxicity of various permethrin and natural pyrethrins (Joffe et al, 2012;Gross et al, 2017b). The mechanism of this enhancement has not been fully explored, but it has been suggested that various components within plant essential oils prevent the detoxification of pyrethroids and other insecticides.…”

“…Plant essential oils and their constituents represent promising additives to insecticides. Numerous studies have demonstrated that plant terpenoids act at a variety of molecular targets (Miyazawa & Kameoka, 1997;Mills et al, 2004;Lopez & Pascual-Villalobos, 2010;Tong & Coats, 2010;Anderson & Coats, 2012;Gross et al, 2017b). Many of these targets are distinct from mammalian targets and therefore these constituents should be safer for humans and non-target animals (Isman, 2000).…”

Rapid Immobilization of Adult Aedes aegypti Caused By Plant Essential Oils At Sublethal Concentrations

“…The bioactivity of plant essential oils is rooted in diverse molecular mechanisms of action that lead to rapid knockdown and/or mortality of exposed insects. These active sites include, but are not limited to, octopamine receptors, tyramine receptors, acetylcholinesterase, nicotinic acetylcholine receptors, and gamma-aminobutyric acid-gated chloride channels (Essam 2001, Anderson and Coats 2012, Tong et al 2012, Gross et al 2017b. Numerous other studies suggest that other sites of toxic action may be involved.…”

A Roadmap for Tick-Borne Flavivirus Research in the “Omics” Era

“…Microbial insecticides based on the fungi Metarhizium anisopliae and Beauveria bassiana have been proposed as environmentally benign alternatives (Benjamin et al, 2002 ; Hornbostel et al, 2004 , 2005 ; Ostfeld et al, 2006 ), and other “green” technologies are under consideration (Benelli et al, 2016 ). Insecticides based on plant-derived extracts are attracting attention as new classes of tick repellants and toxicants, and are the subject of ongoing mode of action studies (Gross et al, 2015 , 2017 ).…”

“…High throughout chemical screening (HTS), followed by “hit-to-lead” and structure-activity studies (SAR) were used to discover several chemistries with high in vitro potency for the receptor (Meyer et al, 2011 ; Ejendal et al, 2012 ) that may provide leads for new pesticides. Research has also focused on pharmacological characterization of the R. microplus octopamine receptor, a suspected target of botanical insecticides (Gross et al, 2015 , 2017 ), and an I. scapularis ligand-gated chloride channel considered the target of ivermectin (Gulia-Nuss et al, 2016 ). These proteins could be used in small molecule screens and targeted by genetic control strategies based on dsRNA/siRNA-mediated RNAi knock-down or Crispr/Cas9 knock out, although protocols for efficient tick transformation would be required for success of the latter.…”