Differential transcriptome profiling of the diapause and cold-responsive genes in unfed adult Dermacentor silvarum Olenev (Acari: Ixodidae)

The tick Dermacentor silvarum mainly overwinters in northern China as an unfed adult entering diapause; however, little is known about the involvement of genes and pathways in summer diapause and overwintering adults of this species. Hence, we investigated the differential transcriptome profile of D. silvarum ticks' diapause and cold-responsive genes and pathways during its summer diapause, overwintering, and questing/active stages. Through transcriptomic sequencing, a total of 136,740 unigenes were assembled, and 1,549, 2,196, and 2,125 differentially expressed genes (DEG) were identified in active and diapause, diapause and overwintering, and active and overwintering ticks, respectively. Between active and diapause ticks, 875 genes were up-regulated, while 674 genes were found down-regulated in diapause ticks. When compared with active ticks, overwintering ticks had 993 up-regulated genes and 1,132 down-regulated genes. Comparison between diapause and overwintering ticks revealed 745 up-regulated and 1,451 down-regulated genes in overwintering ticks. Gene Ontology analysis revealed that, among the active, diapause, and overwintering ticks, most of the DEGs in molecular function were enriched in catalytic activity and hydrolase activity. In the cellular component, most DEGs were assigned to the integral component of the cell membrane, whereas the oxidation-reduction process was the most enriched among biological processes. In addition, the lysosome pathway was the most enriched pathway identified in KEGG pathway analysis. The above results deepened our understanding of the mechanism underlying diapause and overwintering adaptation of ticks, which is important for integrative prevention and control of ticks and tick-borne diseases.