Transcriptomic and Physio-Biochemical Responses of the Fifth-Instar Larvae of Chilo sacchariphagus to High-Temperature Stress
Chilo sacchariphagus is a destructive sugarcane borer worldwide, and frequent extreme high temperatures disrupt its field populations. Clarifying larval thermal response mechanisms provides theoretical support for pest risk prediction under climate warming. Previous work has illustrated moderate heat induces canonical HSP activation, but the molecular responses of this pest to 41 °C extreme heat remain unclear. As such, we conducted non-reference transcriptome sequencing and 11 physio-biochemical assays on fifth-instar larvae exposed to 41 °C for 12 h (26 °C as control) to characterize its thermal regulatory network. De novo assembly yielded a comprehensive transcriptome resource, and analysis of differentially expressed genes revealed enrichment in energy metabolism, ER protein processing, MAPK signaling and autophagy pathways. Core HSP70/40 transcripts were significantly down-regulated while HSP80 showed stable transcription, suggesting that 41 °C may exceed the heat-shock protective threshold and potentially trigger heat damage. qRT-PCR validation of seven core stress genes confirmed the RNA-seq trends. Catalase (CAT) activity increased significantly; however, none of the annotated catalase genes showed transcriptional changes, whereas elevated CarE and AchE activities also lacked corresponding transcriptional shifts, implying post-translational or alternative regulatory mechanisms. Our data showed coordinated transcriptional and physiological changes under extreme heat. These findings provide a basis for further investigation into how C. sacchariphagus may respond to extreme heat under climate warming scenarios.