Heat tolerance is a key parameter that affects insect distribution and abundance. Glyphodes pyloalis Walker (Lepidoptera: Pyralidae) is a devastating pest of mulberry in the main mulberry-growing regions and can cause tremendous losses to sericulture by directly feeding on mulberry leaves and transmitting viruses to Bombyx mori. Moreover, G. pyloalis shows a prominent capacity for adaptation to daily and seasonal temperature fluctuations and can survive several hours under high temperature. To date, the molecular mechanism underlying the outstanding adaptability of this pest to high temperature remains unclear. In this study, we performed comparative transcriptome analyses on G. pyloalis exposed to 25 and 40 °C for 4 h. We obtained 34,034 unigenes and identified 1275 and 1222 genes significantly upregulated or downregulated, respectively, by heat stress. Data from the transcriptome analyses indicated that some processes involved in heat tolerance are conserved, such as high expression of heat shock protein (HSP) genes and partial repression of metabolism progress. In addition, vitamin digestion and absorption pathways and detoxification pathways identified here provided new insights for the investigation of the molecular mechanisms of heat stress tolerance. Furthermore, transcriptome analysis indicated that immune and phosphatidylinositol signaling system have a close relationship with heat tolerance. In addition, the expression patterns of ten randomly selected genes, such as HSP and cytochrome P450, were consistent with the transcriptome results obtained through quantitative real-time PCR. Comparisons among transcriptome results revealed the upregulation of HSPs and genes involved in redox homeostasis, detoxication, and immune progress. However, many metabolism progresses, such as glycolysis/gluconeogenesis and fatty acid biosynthesis, were partially repressed. The results reflected that the heat tolerance of G. pyloalis is a fairly complicated process and related to a broad range of physiological regulations. Our study can improve understanding on the mechanisms of insect thermal tolerance.

Silkworm pupae (Bombyx mori) are a high-protein nutrition source consumed in China since more than 2 thousand years ago. Recent studies revealed that silkworm pupae have therapeutic benefits to treat many diseases. However, the ability of the compounds of silkworm pupae to inhibit tumourigenesis remains to be elucidated. Here, we separated the protein of silkworm pupae and performed alcalase hydrolysis. Silkworm pupa protein hydrolysate (SPPH) can specifically inhibit the proliferation and provoke abnormal morphologic features of human gastric cancer cells SGC-7901 in a dose- and time-dependent manner. Moreover, flow cytometry indicated that SPPH can induce apoptosis and arrest the cell-cycle in S phase. Furthermore, SPPH was shown to provoke accumulation of reactive oxygen species (ROS) and depolarization of mitochondrial membrane potential. Western blotting analysis indicated that SPPH inhibited Bcl-2 expression and promoted Bax expression, and subsequently induced apoptosis-inducing factor and cytochrome C release, which led to the activation of initiator caspase-9 and executioner caspase-3, cleavage of poly (ADP-ribose) polymerase (PARP), eventually caused cell apoptosis. Moreover, SPPH-induced S-phase arrest was mediated by up-regulating the expression of E2F1 and down-regulating those of cyclin E, CDK2 and cyclin A2. Transcriptome sequencing and gene set enrichment analysis (GSEA) also revealed that SPPH treatment could affect gene expression and pathway regulation related to tumourigenesis, apoptosis and cell cycle. In summary, our results suggest that SPPH could specifically suppress cell growth of SGC-7901 through an intrinsic apoptotic pathway, ROS accumulation and cell cycle arrest, and silkworm pupae have a potential to become a source of anticancer agents in the future.