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Int J Parasitol. 2018 Mar;48(3-4):211-224. doi: 10.1016/j.ijpara.2017.08.018. Epub 2017 Dec 16.

Identification and characterization of proteins in the Amblyomma americanum tick cement cone.

Author information

1
Department of Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, TX, USA.
2
Department of Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, TX, USA; Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
3
Centro de Pesquisas em Biologia Molecular e Funcional, Instituto Nacional de Ciência e Tecnologia em Tuberculose (INCT-TB), Pontifícia Universidade Católica do Rio Grande do Sul (PUCRS), Porto Alegre, RS, Brazil; Department of Chemical Physiology, The Scripps Research Institute, La Jolla, CA, USA; Mass Spectrometry Core, Salk Institute for Biological Studies, La Jolla, CA, USA.
4
Department of Chemical Physiology, The Scripps Research Institute, La Jolla, CA, USA; Mass Spectrometry Core, Salk Institute for Biological Studies, La Jolla, CA, USA.
5
Department of Chemical Physiology, The Scripps Research Institute, La Jolla, CA, USA.
6
Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil; Faculdade de Veterinária, Universidade Federal do Rio Grande do Sul, Porto Alegre, RS, Brazil.
7
Department of Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, TX, USA. Electronic address: amulenga@cvm.tamu.edu.

Abstract

The adaptation of hard ticks to feed for long periods is facilitated by the cement cone, which securely anchors the tick mouthparts onto host skin and protects the tick from being groomed off by the host. Thus, preventing tick cement deposition is an attractive target for the development of innovative tick control. We used LC-MS/MS sequencing to identify 160 Amblyomma americanum tick cement proteins that include glycine-rich proteins (GRP, 19%), protease inhibitors (12%), proteins of unknown function (11%), mucin (4%), detoxification, storage, and lipocalin at 1% each, and housekeeping proteins (50%). Spatiotemporal transcription analysis showing mRNA expression in multiple tick organs and transcript abundance increasing with feeding suggest that selected GRPs (n = 13) regulate multiple tick feeding functions, being classified as constitutively expressed (CE), feeding induced (FI), and up-regulated with feeding (UR). We show that transcription of CE GRPs is likely under the control of tick appetence associated factors in that mRNA abundance increased several thousand fold in 1 week old adult ticks, the time period that coincides with tick attainment of appetence. Given the high number of targets, we synthesized and injected unfed ticks with combinatorial (co) double stranded (ds)RNA and disrupted GRP mRNA in clusters according to similar transcription patterns: CE (n = 3), FI, (n = 4), and UR (n = 6) to streamline the work. Our data suggest that CE and FI GRPs are important for maintenance of the tick feeding site in that reddening and subsequent bleeding were observed around the mouthparts of CE and FI GRP co-dsRNA injected ticks during feeding. Furthermore, although not significantly different, indices for blood meal size and fecundity were apparently reduced in FI and UR ticks. We discuss our data with reference to A. americanum tick feeding physiology.

KEYWORDS:

Amblyomma americanum; Combinatorial RNAi silencing; LC-MS/MS sequencing; Tick attachment; Tick cement cone

PMID:
29258831
PMCID:
PMC5844823
DOI:
10.1016/j.ijpara.2017.08.018
[Indexed for MEDLINE]
Free PMC Article

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