title: Targeted silencing of the Aquaporin 2 gene of Rhipicephalus (Boophilus) microplus reduces tick fitness.
abstract: BACKGROUND
  Ticks are blood-feeding arthropods that can affect human and animal health both directly by blood-feeding and indirectly by transmitting pathogens. The cattle tick Rhipicephalus (Boophilus) microplus is one of the most economically important ectoparasites of bovines worldwide and it is responsible for the transmission of the protozoan Babesia bovis, the etiological agent of bovine babesiosis. Aquaporins (AQPs) are water channel proteins implicated in physiological mechanisms of osmoregulation. Members of the AQP family are critical for blood-feeding arthropods considering the extreme osmoregulatory changes that occur during their feeding. We investigated the pattern of expression of a newly identified AQP2 gene of R. microplus (RmAQP2) in different tick tissues and stages. We also examined in vivo the biological implications of silencing expression of RmAQP2 silencing during tick feeding on either uninfected or B. bovis-infected cattle.
  
  
  METHODS
  In silico gene analyses were performed by multiple alignments of amino acid sequences and topology prediction. Levels of RmAQP2 transcripts in different tick tissues and stages were analyzed by reverse transcriptase quantitative PCR. Patterns of expression of RmAQP2 protein were investigated by immunoblots. Gene silencing was performed by RNA interference and in vivo functional analyses carried out by feeding ticks on either uninfected or B. bovis-infected cattle.
  
  
  RESULTS
  RmAQP2 transcripts were found in unfed larvae, engorged nymphs, and salivary glands and guts of partially engorged females; however, of all tick tissues and stages examined, RmAQP2 protein was found only in salivary glands of partially engorged females. RmAQP2 silencing significantly reduced tick fitness and completely abrogated protein expression. The effect of RmAQP2 silencing on fitness was more pronounced in females fed on a B. bovis-infected calf than in ticks fed on an uninfected calf and none of their larval progeny survived.
  
  
  CONCLUSIONS
  Collectively, considering the gene expression and tick fitness data, we conclude that RmAQP2 is critical for tick blood feeding and may be a suitable candidate target for the development of novel strategies to control R. microplus and tick-borne parasites.
authors.affiliation: Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, WA, 99164, USA. hala@vetmed.wsu.edu.|Department of Entomology, Faculty of Science, Cairo University, Giza, 12613, Egypt. hala@vetmed.wsu.edu.
authors.forename: Hala E
authors.initials: HE
authors.lastname: Hussein
authors.affiliation: Animal Disease Research Unit, USDA-ARS, Washington State University, 3003 ADBF, P.O. Box 646630, Pullman, WA, 99164, USA. scoles@vetmed.wsu.
authors.forename: Glen A
authors.initials: GA
authors.lastname: Scoles
authors.affiliation: Animal Disease Research Unit, USDA-ARS, Washington State University, 3003 ADBF, P.O. Box 646630, Pullman, WA, 99164, USA. massaro@vetmed.wsu.edu.
authors.forename: Massaro W
authors.initials: MW
authors.lastname: Ueti
authors.affiliation: Animal Disease Research Unit, USDA-ARS, Washington State University, 3003 ADBF, P.O. Box 646630, Pullman, WA, 99164, USA. ces@vetmed.wsu.edu.
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Suarez
authors.affiliation: Department of Entomology, Faculty of Science, Cairo University, Giza, 12613, Egypt. adhamfk@gmail.com.
authors.forename: Fatma K
authors.initials: FK
authors.lastname: Adham
authors.affiliation: USDA-ARS, Knipling Bushland US Livestock Insect Research laboratory, 2700 Fredericksburg Road, Kerrville, TX, 78028, USA. Felix.Guerrero@ars.usda.gov.|USDA-ARS Veterinary Pest Genomics Center, Kerrville, TX, USA. Felix.Guerrero@ars.usda.gov.
authors.forename: Felix D
authors.initials: FD
authors.lastname: Guerrero
authors.affiliation: School of Molecular Biosciences, Washington State University, Pullman, WA, 99164, USA. rgbastos@vetmed.wsu.edu.
authors.forename: Reginaldo G
authors.initials: RG
authors.lastname: Bastos
mesh_terms: D000818:Animals; D051399:Aquaporin 2 / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism*; D060829:Arthropod Proteins / Q000037:antagonists & inhibitors / Q000235:genetics* / Q000378:metabolism*; D001404:Babesiosis; D002417:Cattle; D002418:Cattle Diseases; D005247:Feeding Behavior; D020869:Gene Expression Profiling; D020868:Gene Silencing; D008969:Molecular Sequence Data; D048494:Rhipicephalus / Q000235:genetics / Q000502:physiology*; D017422:Sequence Analysis, DNA
chemical_list: D051399:Aquaporin 2; D060829:Arthropod Proteins