Sequential expression of heat shock proteins 70 contributing to the heat response of Haemaphysalis longicornis (Acari: Ixodidae).

The hard tick Haemaphysalis longicornis serves as a vector for multiple pathogens and can cause severe tick-borne diseases. Temperature is a key environmental factor influencing its population dynamics and disease transmission risk. As a crucial molecular mechanism underlying thermal adaptation, the upregulation of heat shock protein 70 (Hsp70) is generally regarded as an important adaptive response of organisms to heat stress. We systematically identified seven Hsp70s (designated as HlHsp70.1, HlHsp70.2, HlHsp70.3, HlHsp70.4, HlHsp70.5, HlHspa5, HlHspa9) in H. longicornis and comprehensively analyzed their physicochemical properties, phylogenetic relationships, and expression patterns. Quantitative real-time PCR results revealed that the expression patterns of HlHsp70s were significantly influenced by the duration and intensity of heat treatment. Under 35°C treatment, most HlHsp70 genes (except HlHspa9) were upregulated after 2 h. After 45°C treatment, most HlHsp70 genes reached their expression peaks within 1 h. Notably, HlHsp70.1, HlHsp70.2, and HlHsp70.3 exhibited particularly remarkable upregulation, with HlHsp70.2 showing a maximum increase of 1973.71-fold, while HlHspa9 expression remained unchanged. At 45°C, the mortality of H. longicornis was significantly increased after RNA interference of HlHsp70.1, HlHsp70.2, and HlHsp70.3 (p < 0.01). It indicates that HlHsp70.1, HlHsp70.2, and HlHsp70.3 play critical roles in the thermotolerance of H. longicornis. This study elucidates the important function of the Hsp70 gene family in the heat stress response of H. longicornis, providing a theoretical basis for understanding its environmental adaptation and exploring control strategies for tick-borne diseases.