Insect cold hardiness: the role of mitogen‐activated protein kinase and Akt signalling in freeze avoiding larvae of the goldenrod gall moth, Epiblema scudderiana

Abstract

Larvae of the goldenrod gall moth, Epiblema scudderiana, use the freeze avoidance strategy of cold hardiness to survive the winter. Here we report that protein kinase-dependent signal transduction featuring mitogen-activated protein kinase (MAPK) signalling cascades (extracellular signal regulated kinase, c-jun N-terminal kinase and p38 MAPK pathways) and the Akt (also known as protein kinase B, or PKB) pathway could be integral parts of the development of cold hardiness by E. scudderiana. We used Luminex technology to assess the protein levels and phosphorylation status of key components and downstream targets of those pathways in larvae in response to low temperature acclimation. The data showed that MAPK pathways (both total protein and phosphorylated MAPK targets) were inhibited after 5°C acclimation, but not -15°C exposure, as compared with the 15°C control group. However, total heat shock protein 27 (HSP27) levels increased dramatically by ∼12-fold in the -15°C acclimated insects. Elevated HSP27 may facilitate anti-apoptotic mechanisms in an Akt-dependent fashion. By contrast, both 5 and -15°C acclimation produced signs of Akt pathway activation. In particular, the inhibitor phosphorylated Glycogen Synthase Kinase 3a (p-GSK3) levels remained high in cold-exposed larvae. Additionally, activation of the Akt pathway might also facilitate inhibition of apoptosis independently of GSK3. Overall, the current study indicates that both MAPK and Akt signal transduction may play essential roles in freeze avoidance by E. scudderiana.

Transcriptomic and proteomic analyses of the mechanisms of overwintering diapause in soybean pod borer (Leguminivora glycinivorella)

“…50 Up-regulated genes in diapause-destined insects were closely related to lipid metabolism, energy production and conversion, carbohydrate metabolism and transport, and molecular chaperones. 29,30,[50][51][52] In our work, RNA-Seq transcriptomics and TMT proteomics analysis showed similar results. Among the 15 synchronously up-regulated proteins in diapause-destined L. glycinivorella larvae, six proteins were involved in fat metabolism and molecular chaperones (Table S5).…”

“…19 To date, the function of FAS in insects has been thoroughly studied only in the cabbage beetle, German cockroach, and several Drosophila species. 35,40,51 In Drosophila serrata, silencing of FASN3 was lethal. 50 Silencing FAS2 with RNAi caused clumping of the fat body and reduced the total triacylglyceride content of diapause-destined female cabbage beetles.…”

“…30 Protein levels of Hsp70, Hsp60, and Hsp40 are consistently elevated over the winter months in the larvae of goldenrod gall moth, Epiblema scudderiana, which indicates that HSPs play significant roles in the winter-cold hardiness. 51 Recent studies have shown that sHSPs in insects may also play a critical role in development. [57][58][59][60] For instance, Hsp22 over-expression extended lifespan by 32%, and silencing of Hsp22 reduced lifespan by 40% in Drosophila melanogaster.…”

Amplification and quantification of cold‐associated microRNAs in the Colorado potato beetle (Leptinotarsa decemlineata) agricultural pest

“…Elevated levels of phosphorylated‐Akt were detected in −15 °C‐exposed Ep. scudderiana larvae when compared to control larvae (Zhang & Storey, ), whereas a transcriptomics approach in overwintering Chinese white wax scale insects, Ericerus pela , detected significant changes in levels of several transcripts associated with the PI3K‐Akt signalling pathway (Yu et al ., ). Expression levels and activity assessment of key PI3K pathway effectors in cold‐exposed Colorado potato beetles would provide additional leads as to the relevance of the bantam‐3p regulated Trbl‐PI3K/Akt pathway in these insects at low temperatures.…”

Elevated chaperone proteins are a feature of winter freeze avoidance by larvae of the goldenrod gall moth, Epiblema scudderiana

“…This suggests that the seasonal acquisition of HSPs by the larvae may be linked, at least in part, to declining ambient temperatures. Indeed, we have also recently reported a strong 11.6-fold upregulation of Hsp27 levels in E. scudderiana larvae after acute transfer to −15°C for 3 weeks, as compared with larvae held at 15°C or 5°C (Zhang and Storey, 2017). Other factors that may have substantial regulatory influences on the acquisition and maintenance of HSPs over the winter may include entry into diapause as well as changing photoperiod which is known to influence antifreeze protein production in freeze avoiding insects (Duman, 2001).…”