Molecular characterization and modulated expression of histone acetyltransferases during cold response of the tick Dermacentor silvarum (Acari: Ixodidae)

Abstract

Background Histone acetylation is involved in the regulation of stress responses in multiple organisms. Dermacentor silvarum is an important vector tick species widely distributed in China, and low temperature is a crucial factor restricting the development of its population. However, knowledge of the histone acetyltransferases and epigenetic mechanisms underlying cold-stress responses in this tick species is limited. Methods Histone acetyltransferase genes were characterized in D. silvarum, and their relative expressions were determined using qPCR during cold stress. The association and modulation of histone acetyltransferase genes were further explored using RNA interference, and both the H3K9 acetylation level and relative expression of KAT5 protein were evaluated using western blotting. Results Three histone acetyltransferase genes were identified and named as DsCREBBP, DsKAT6B, and DsKAT5. Bioinformatics analysis showed that they were unstable hydrophilic proteins, characterized by the conserved structures of CBP (ZnF_TAZ), PHA03247 super family, Creb_binding, and MYST(PLN00104) super family. Fluorescence quantitative PCR showed that the expression of DsCREBBP, DsKAT6B, and DsKAT5 increased after 3 days of cold treatment, with subsequent gradual decreases, and was lowest on day 9. Western blotting showed that both the H3K9 acetylation level and relative expression of KAT5 in D. silvarum increased after treatment at − 4, 4, and 8 °C for 3 and 6 days, whereas they decreased significantly after a 9-day treatment. RNA interference induced significant gene silencing, and the mortality rate of D. silvarum significantly increased at the respective semi-lethal temperatures. Conclusion These results imply that histone acetyltransferases play an important role in tick adaptation to low temperatures and lay a foundation for further understanding of the epigenetic regulation of histone acetylation in cold-stressed ticks. Further research is needed to elucidate the mechanisms underlying histone acetylation during cold stress in ticks. Graphical Abstract

Molecular characterization and induced changes of histone acetyltransferases in the tick Haemaphysalis longicornis in response to cold stress

“…Histone modifications and histone-modifying enzymes play pivotal roles in the regulation of transcription, which is highly dynamic in response to stress [ 31 ]. Several HAT genes have been cloned from species of ticks, including D. silvarum , Ixodes scapularis, and Amblyomma maculatum [ 32 – 34 ]. However, these genes belong to different gene families, and the functions in response to various environmental stresses of the histone-modifying enzymes that they encode are unclear.…”

“…HAT-B is the only known member of the type B histone acetyltransferases that exhibits specificity toward free H4 [ 40 ]. Three HATs, DsCREBBP , DsKAT6B and DsKAT5 , which belong to the p300/CBP (KAT protein family) have been characterized in D. silvarum [ 34 ]. Different expression patterns have been found for distinct categories of HAT genes in response to cold stress in ticks.…”

“…In the present study, the expression of HlGNAT and HlHAT-B initially decreased after 3 days of cold treatment, but then gradually increased with a prolonged period of exposure of H. longicornis to cold. In contrast, the expression of DsCREBBP , DsKAT6B , and DsKAT5 in D. silvarum initially increased in response to cold treatment before gradually decreasing [ 34 ].…”