Gene expression during the early stages of host perception and attachment in adult female Rhipicephalus microplus ticks

Authors: Bendele, Kylie; Guerrero, Felicito; CAMERON, CONNOR - National Center For Genome Resources; Bodine, Deanna; Miller, Robert

Submitted to: Experimental and Applied Acarology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/12/2019
Publication Date: 9/24/2019
Citation: Bendele, K.G., Guerrero, F., Cameron, C., Bodine, D.L., Miller, R. 2019. Gene expression during the early stages of host perception and attachment in adult female Rhipicephalus microplus ticks. Experimental and Applied Acarology. 79(1):107-124. https://doi.org/10.1007/s10493-019-00420-1.
DOI: https://doi.org/10.1007/s10493-019-00420-1

Interpretive Summary: The cattle tick, Rhipicephalus microplus, is a serious pest of cattle, with significant economic consequences to the livestock industries of tropical and semitropical countries. R. microplus belongs to the Metastriata group of the Ixodidae family known as hard ticks. When adult hard ticks feed, mating has not yet occurred and the entire feeding process takes several days to complete. There is an initial phase of 1-2 days whereby the tick attaches to the bovine host. This attachment phase is followed by a slow blood feeding phase that can last several days until mating occurs. Upon mating, blood feeding concludes with a rapid engorgement phase that is completed in 12-36 hours. At this time, the replete female tick drops off the host and deposits her eggs. Our group's interest in mining the genome and transcriptome of R. microplus for novel targets for development of tick control technologies led us to investigate the early molecular events occurring upon tick attachment and subsequent feeding. We used a strategy designed to identify differential gene expression in the very early phase of tick attachment and feeding. We placed newly molted unfed adult R. microplus females upon a bovine host and harvested the attached ticks after 3, 6, 12, and 24 hr. We also placed a group of these ticks in a gas-permeable bag taped onto the side of the bovine host. These ticks were able to sense the host but unable to penetrate the bag to begin attachment and were ultimately harvested after 3 hr. This study reports results from RNASeq and differential gene expression analysis of these sample transcriptomes, identifying specific transcripts that were differentially expressed in the 3 hr attached ticks compared to unfed controls and also in the 3 hr attached ticks compared to 3 hr host-exposed ticks.

Technical Abstract: The cattle tick, Rhipicephalus microplus, is a serious pest of cattle, with significant economic consequences to the livestock industries of tropical and semitropical countries. R. microplus belongs to the Metastriata group of the Ixodidae family known as hard ticks. When adult hard ticks feed, mating has not yet occurred and an initial host attachment phase of 1-2 days is followed by a slow feeding phase that can last several days. Once mating occurs, feeding concludes with a rapid engorgement phase that is completed in 12-36 hours. Our group's interest in mining the genome and transcriptome of R. microplus for novel targets for development of tick control technologies led us to investigate the early transcriptional events occurring upon tick attachment and subsequent feeding. We used a strategy designed to identify differential gene expression in the very early phase of tick attachment and feeding. We placed newly molted unfed adult R. microplus females upon a bovine host and harvested the attached ticks after 3, 6, 12, and 24 hr. We also placed a group of these ticks in a gas-permeable bag taped onto the side of the bovine host. These ticks were able to sense the host but unable to penetrate the bag to begin attachment and were ultimately harvested after 3 hr. This study reports results from RNASeq and differential gene expression analysis of these sample transcriptomes, identifying specific transcripts that were differentially expressed in the 3 hr attached ticks compared to unfed controls and also in the 3 hr attached ticks compared to 3 hr host-exposed ticks.