Sustaining Induced Heat Shock Protein 70 Confers Biological Thermotolerance In A High-Temperature Adapted Predatory Miteneoseiulus Barkeri(Hughes)

BACKGROUND In fluctuating climatic environments, heat acclimation in predatory mites is a superior adaptation strategy for effective agricultural pest management and can be used to enhance the abilities critical in biological control efficiency. We investigated the regulatory mechanism governing the remarkable plastic response of thermotolerance in a high-temperature adapted strain (HTAS) and discerned the differences in the defensive reactions between the HTAS and the conventional strain (CS) in the predatory miteNeoseiulus barkeri. RESULTS At 42 degrees C, the relative expression levels of four identified HSP70 genes increased rapidly in bothN. barkeristrains; meanwhile the expression ofNbHSP70-1andNbHSP70-2in CS sharply decreased after 4 h, displaying a distinct contrast with the remaining elevated expression in HTAS.Western blot analysis showed that the protein level ofNbHSP70-1in CS was dramatically elevated at 0.5 h and decreased at 6 h at 42 degrees C. Conversely, in HTAS,NbHSP70-1was constantly induced and peaked at 6 h at 42 degrees C. Furthermore, HSP70 suppression by RNAi knockdown had a greater influence on the survival of HTAS, causing a higher mortality under high temperature than CS. Finally, the recombinant exogenousNbHSP70-1protein enhanced the viability ofE. coliBL21 under a lethal temperature of 50 degrees C. CONCLUSION Sustained accumulation of HSP70 proteins results in predatory phytoseiid mites with the thermotolerance advantage that could promote their biological control function to pests. The divergent constitutive regulation of HSP70 to a thermal environment is conducive to the flexible adaptability of predators in the higher trophic level to trade off under extremely adversity stress.