|WULFF, JUAN - Texas A&M University|
|Lohmeyer, Kimberly - Kim|
|PEITROANTONIO, PATRICIA - Texas A&M University|
Submitted to: Parasites & Vectors
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/24/2022
Publication Date: 10/6/2022
Citation: Wulff, J.P., Temeyer, K.B., Tidwell, J.P., Schlechte, K.G., Lohmeyer, K.H., Peitroantonio, P.V. 2022. Periviscerokinin (Cap2b; CAPA) receptor silencing in females of Rhipicephalus microplus reduces survival, weight, and reproductive output. Parasites & Vectors. https://doi.org/10.1186/s13071-022-05457-7.
Interpretive Summary: Cattle fever ticks vector pathogens that cause serious diseases in cattle, worldwide. Although the ticks were considered to be eradicated from the United States, they remain endemic in Mexico and recurrent outbreaks within South Texas are increasingly difficult to eradicate or control, presenting a serious threat to U.S. cattle producers. Ticks have developed resistance to nearly all available acaricides and there is an urgent need to develop new and effective methods for tick control. G-protein coupled receptors (GPCRs) in ticks are involved in regulating tick development and reproduction and offer significant potential for development of novel chemical acaricides. New research utilizing gene silencing of tick GPCRs conducted by scientists at the U.S. Department of Agriculture and Texas A&M University revealed the potential of several GPCRs to alter tick physiological processes resulting in reduced tick fitness and reproduction. One of these GPCRs, known as a type of kinin receptor, appeared to be involved in tick development, feeding, growth, and reproduction, providing substantial evidence that this system may have strong potential as a promising target for novel tick control.
Technical Abstract: Background: The cattle-fever tick, Rhipicephalus (Boophilus) microplus, is a vector of pathogens causative of babesiosis and anaplasmosis, both highly lethal bovine diseases that affect cattle worldwide. In metazoans, neuropeptides and their G protein-coupled receptors (GPCRs) play a critical integrative role in the regulation of all physiological processes. However, the physiological activity of many neuropeptides is still unknown in ticks. Periviscerokinins (CAP2b/PVKs) are neuropeptides associated with myotropic and diuretic activities in insects. These peptides have been identified only in a few tick species, such as Ixodes ricinus, Ixodes scapularis and R. microplus, and their cognate receptor only characterized for the last two. Methods: The periviscerokinin receptor (Rhimi-CAP2bR) expression was investigated throughout stages of R. microplus, and silenced by RNA interference in the females. In a first experiment, three dsRNAs named ds680-805, ds956-1109 and ds1102-1200 were tested in vivo, and while the three caused phenotypic effects, the last one was chosen for subsequent experiments. Resulting RNAi phenotypic variables were compared to those of negative controls, both non-injected and dsRNA beta-lactamase-injected ticks, and to positive controls injected with beta-actin dsRNA. Rhimi-CAP2bR silencing was verified by quantitative reverse-transcriptase PCR (qRT-PCR) in whole females and dissected tissues. Results: Rhimi-CAP2bR transcript expression was detected throughout all developmental stages. Rhimi-CAP2bR silencing was associated with increased female mortality, decreased weight of surviving females and of egg masses, a delayed egg incubation period, and decreased egg hatching (P < 0.05). Conclusions: CAP2b/PVKs appears to be associated with the regulation of female feeding, reproduction and survival. Since the Rhimi-CAP2bR loss of function was detrimental to females, the discovery of antagonistic molecules of the CAP2b/PVK signaling system should cause similar effects. Our results point to this signaling system as a promising target for tick control.