Starvation Induces Endoplasmic Reticulum Stress and Autophagy in Malpighian Tubules of Two-Spotted Field Crickets Gryllus bimaculatus

ABSTRACT: We investigated gene expression related to endoplasmic reticulum (ER) stress, apoptosis, and autophagy to understand how Gryllus bimaculatus (two-spotted field cricket) overcomes starvation stress. Male adults were used in starvation experiments. Expression levels of genes related to ER stress, apoptosis, and autophagy were investigated for each tissue after starvation stress (consisting of 1, 3, and 6 days of starvation, and 1 and 2 days of refeeding after 6 days of starvation) by reverse-transcription PCR. Furthermore, Malpighian tubules were stained with LysoTracker Red to observe autophagy. Starvation significantly upregulated gene expression of ER chaperones in the Malpighian tubules of G. bimaculatus. Gene expression levels of BiP, ERap2, and SERCA were upregulated up to 2.5-fold, ATF6 was upregulated up to 2-fold, and PDI and Derl2 were upregulated up to 1.5-fold in the starvation group compared to controls. Although autophagy was induced by starvation, apoptosis was not. Notably, gene expression of ATG9 was upregulated up to 15-fold in the Malpighian tubules of G. bimaculatus, which is the highest among the autophagy-related genes. These results suggest that ER stress-induced autophagy appears to be acutely involved in the mechanism by which insects overcome starvation stress.