Sequential expression of small heat shock proteins contributing to the cold response of Haemaphysalis longicornis (Acari: Ixodidae)

Abstract

BACKGROUNDHaemaphysalis longicornis is an important livestock pest and a serious threat to public health. Cold stress is a common form of stress affecting its survival and distribution. However, H. longicornis exhibits different physiological responses to cold stress. In this study, we systematically explored the regulation and functions of small heat shock proteins (sHsps) in H. longicornis during cold stress.RESULTSSeven sHsp genes (HlsHsp14.9, HlsHsp19.9, HlsHsp20.3, HlsHsp21.4, HlsHsp23.7, HlsHsp24.0, and HlsHsp26.1) with open reading frame lengths ranging from 408 bp (HlsHsp14.9) to 673 bp (HlsHsp26.1) were cloned from H. longicornis, which were featured with the typical α‐crystallin domain. Phylogenetic analysis revealed high similarity with the sHsps of arachnid species. Quantitative polymerase chain reaction revealed that the regulation of sHsp genes depended on the severity and duration of cold treatment. Moreover, the relative expression of each gene was largely dependent on the treatment periods (P < 0.01; 3, 6, and 9 d of treatment at 8, 4, 0, and –4 °C). Among all genes, HlsHsp14.9, HlsHsp19.9, HlsHsp20.3, and HlsHsp24.0 were most sensitive to rapid cold treatment. After RNA interference, the mortality of H. longicornis was significantly increased at –14 °C (P < 0.05), suggesting that the expression of sHsp genes is closely related to the cold tolerance of H. longicornis.CONCLUSIONOur results indicate that sHsps play an important role in the cold stress response of H. longicornis, which may enhance our understanding of the cold adaptation mechanisms in ticks.This article is protected by copyright. All rights reserved.