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

## TL;DR

This study explores how the predatory mite Neoseiulus californicus adapts to extreme heat by analyzing its transcriptome and the role of a specific heat shock protein, HSP70.

## Contribution

The study identifies NcHSP70 as a key gene in heat tolerance and provides insights into molecular mechanisms of heat adaptation in phytoseiid mites.

## Key findings

- NcHSP70 gene showed the highest expression under high temperature exposure.
- RNAi suppression of NcHSP70 significantly reduced mite survival under heat stress.
- ATPase activity of NcHSP70 increased after heat treatment, indicating functional importance.

## Abstract

Neoseiulus californicus, a key biological control agent against phytophagous mites and small insects, is adapted to exposure to relatively high temperatures (HTs) (35–45 °C). Herein, transcriptome sequencing analysis was conducted on N. californicus under 25 °C and 45 °C exposures. Gene functional analysis illustrated that the DEGs were primarily participating in “catalytic activity”, “immune system process”, and the “Calcium signaling pathway”. Furthermore, we identified a heat shock protein 70 gene (NcHSP70) that displayed the highest expression under HT exposure. Functional analysis of RNAi and ATPase activity revealed the important roles of NcHSP70 involved in the heat tolerance of N. californicus. Our outcomes contribute to a deeper comprehension of the HT adaptation of phytoseiid mites and offer a reference for developing sustainable biocontrol strategies for small sap-feeding pests under a global warming environment.

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.