Sec61s and Sec62/Sec63 Genes Are Essential for Survival by Regulating the Gut and Cuticle Development in Locusta migratoria

In eukaryotes, a lot of proteins are transported across the endoplasmic reticulum by the heterotrimeric Sec61 channel. And post-translational transport needs another Sec62/Sec63 complex. However, functions of these genes are poorly explored in insects. In this study, we first identified five Sec genes, named <i>Sec61α</i>, <i>Sec61β</i>, <i>Sec61γ</i>, <i>Sec62</i> and <i>Sec63</i>, in <i>Locusta migratoria</i>. Quantitative reverse-transcription polymerase chain reaction (RT-qPCR) analysis showed that these five genes were expressed in muti-tissues, including wing pad, leg, foregut, midgut, gastric cecum, hindgut, and highly expressed in the integument. Knockdown of <i>LmSec61α</i> and <i>LmSec61γ</i> by RNA interference (RNAi) lead to the feeding cessation with a mortality rate of 100%. However, there is only 13.4% of ds<i>LmSec61β</i>-injected nymphs died before molting. All nymphs injected with ds<i>LmSec61α</i> and ds<i>LmSec61γ</i> died before molting with the gut atrophy. Furthermore, hematoxylin-eosin staining indicated that the cells of the midguts and gastric caecum were defective, and the microvilli and peritrophic matrix were destroyed seriously after silencing <i>LmSec61α</i> and <i>LmSec61γ</i>. Knockdown of <i>LmSec62</i> and <i>LmSec63</i> resulted in high mortality before and during molting. The hematoxylin-eosin (HE) staining and transmission electron microscopy (TEM) results showed that both the formation of the new cuticle and the degradation of the old cuticle were inhibited in ds<i>LmSec63</i>-injected insects compared to the controls. Especially, there was no obvious plaques on microvillar tips of the epidermal cells after silencing of <i>LmSec63</i>. These results revealed that <i>Sec61s</i> and <i>Sec62</i>/<i>Sec63</i> genes are required in the gut and cuticle development of locusts. Therefore, these genes are potential targets for the control of locusts.