Data from: Metabolomic and transcriptomic responses of ticks during recovery from cold shock reveal mechanisms of survival

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.

蜱虫是吸血的外寄生虫（ectoparasites），但大部分生命周期处于宿主外环境，需耐受冬季低温。快速冷硬化（Rapid cold-hardening, RCH）是节肢动物（包括蜱虫）常用的过程，可提高其在急性低温暴露下的存活率。然而，蜱虫中与RCH、冷休克（cold shock）及这些应激恢复相关的潜在机制尚不清楚。本研究采用转录组学（transcriptomics）与代谢组学（metabolomics）联合方法，探究RCH对美洲犬蜱（Dermacentor variabilis）冷应激恢复过程中基因表达和代谢的影响程度。从RCH恢复后，蜱虫中有1860个基因差异表达，而直接冷休克恢复过程中仅99个基因产生响应。RCH恢复导致多种通路上调，涉及离子结合（ion binding）、转运、代谢及细胞结构——此类响应在其他节肢动物的冷应激反应中亦可见。多种代谢物（metabolites）（包括若干氨基酸（amino acids）和甜菜碱（betaine））的积累与这些分子相关通路中的转录变化一致，表明代谢组（metabolome）和转录组（transcriptome）存在协同变化。接受外源性（exogenous）甜菜碱和缬氨酸（valine）的蜱虫表现出增强的耐寒性，提示这些代谢物具有低温保护作用（cryoprotective effects）。总体而言，蜱虫冷休克恢复过程中的许多响应与其他节肢动物相似，但部分调节机制可能与当前研究的其他类群（taxa）存在差异。