Multigenerational Heat Selection Enhancing Thermal Acclimation and Transcriptional Response of Hsps to Heat Stress in Spodoptera frugiperda Male Adults

In this study, using a multigenerational heat selection design, we investigated the possible pattern of thermal acclimation and the background mechanism in <i>Spodoptera frugiperda</i>. Results show that heat selection significantly shortened the larval and pupal developmental duration, which was maintained in the four tested generations. Significant costs to reproduction were found in the first two generations, but they recovered in the following generations. Heat-selected adults exhibited significantly higher survival rates under extremely high temperatures, and the survival rate increased with subsequent generations. Transcriptomic analysis between heat-selected and non-selected male adults from the first generation showed that heat stress did not induce the upregulation of any heat shock protein (Hsp) genes; in the fourth generation, however, heat stress resulted in the upregulation of a great number of Hsps, indicating a positive correlation between Hsp expression and heat tolerance. Further analysis also found differential expression in other genes associated with heat resistance, such as cuticle-, antioxidant-, and detoxification-related genes. Moreover, quite a number of stress response GO terms were enriched, such as response to heat and other abiotic stimuli. GO enrichment also showed that DEGs were enriched to many more terms related to metabolism. KEGG enrichment revealed that relatively more disease-, metabolism-, and immunity-associated pathways were enriched. The number of disease pathways increased with the selection temperature in the first generation, whereas it decreased with subsequent generations. This study offers new information for the understanding of the thermal acclimation process and mechanism of moth species, and facilitates the prediction and management of this major pest.