Changes in Transcriptome and Functional Evaluation of Heat Shock Protein 70 in Predatory Mite Neoseiulus californicus (Hughes) in Response to Extreme High Temperature

Phytoseiid mites, as effective natural enemies, often experience various environmental stresses, especially extreme HTs under global warming and climate change. However, Neoseiulus californicus from the phytoseiid mite family could endure relatively HT (35–45 °C) exposure. To gain insights into its molecular mechanisms underlying heat adaptation, we conducted a comparative analysis of the transcriptomes exposed at 25 and 45 °C. There were 3117 and 7368 differentially expressed genes (DEGs) identified under the 0.5 and 4 h heat treatments, respectively. The functional enrichment analysis illustrated that DEGs were linked to “catalytic activity”, “metabolic process”, and the “Calcium signaling pathway”. Further DEG annotation and analysis illustrated that the expression of proteins encoding heat shock proteins (HSPs) and protein turnover were significantly induced. We also identified the unigene DN1689_c0 encoding the HSP70 gene (NcHSP70), which exhibited the strongest transcriptional response to heat stress. NcHSP70 inhibition by RNAi suppression had a significant impact on the survival of N. californicus. The ATPase effect of the purified recombinant NcHSP70 protein after HT treatment was significantly elevated. These findings increase our comprehension of the complex molecular mechanisms underlying HT adaptation and determine the important role of NcHSP70 in the heat resistance of N. californicus.