No abstract

Ticks are blood-feeding ectoparasites but spend most of their life off-host where they may have to tolerate low winter temperatures. Rapid cold-hardening (RCH) is a process commonly used by arthropods, including ticks, to improve survival of acute low temperature exposure. However, little is known about the underlying mechanisms in ticks associated with RCH, cold shock, and recovery from these stresses. In the present study, we investigated the extent to which RCH influences gene expression and metabolism during recovery from cold stress in Dermacentor variabilis, the American dog tick, using a combined transcriptomics and metabolomics approach. Following recovery from RCH, 1,860 genes were differentially expressed in ticks, whereas only 99 genes responded during recovery to direct cold shock. Recovery from RCH resulted in an upregulation of various pathways associated with ion binding, transport, metabolism, and cellular structures seen in the response of other arthropods to cold. The accumulation of various metabolites, including several amino acids and betaine, corresponded to transcriptional shifts in the pathways associated with these molecules, suggesting congruent metabolome and transcriptome changes. Ticks receiving exogenous betaine and valine demonstrated enhanced cold tolerance, suggesting cryoprotective effects of these metabolites. Overall, many of the responses during recovery from cold shock in ticks were similar to those observed in other arthropods, but several adjustments may be distinct from other currently examined taxa.

As carriers of multiple human diseases, understanding the mechanisms behind mosquito reproduction may have implications for remediation strategies. Transfer RNA (tRNA) acts as the adapter molecule of amino acids and are key components in protein synthesis and a critical factor in the function of tRNAs is chemical modifications. Here, we provide an assessment of tRNA modifications between sexes for three mosquito species and examine correlated transcript levels underlying key proteins involved in tRNA modification. Thirty-three tRNA modifications were detected among mosquito species and most of these modifications are higher in females compared to males. Analysis of previous male and female RNAseq datasets indicated a similar increase in tRNA modifying enzymes in females, supporting our observed female enrichment of tRNA modifications. Tissues-specific expressional studies revealed high transcript levels for tRNA modifying enzymes in the ovaries for Aedes aegypti, but not male reproductive tissues. These studies suggest that tRNA modifications may be critical to reproduction in mosquitoes, representing a potential novel target for control.