Changes in Saccharide Content and the Role of the PI3K-Akt Signal Transduction Pathway in Silkworm Eggs Treated With HCL to Prevent or Break Diapause

Acid soaking with hydrochloric acid (HCl) is a common method used to prevent or break diapause in silkworm eggs and has been widely applied in production. However, its underlying mechanism remains to be explored. Few studies have reported on the metabolism of mono- or disaccharides, and the differential expression patterns of genes and proteins related to the phosphatidyl inositol 3-kinase (PI3K/)Akt signaling pathway across the stages of silkworm diapause eggs, non-diapause eggs, instant acid-soaked eggs, and red bean color acid-soaked (RBCAS) eggs. In this study, eggs from the silkworm 932 strain at different stages were used to explore the content of several saccharides and analyze the expression profiles of 4 diapause-related genes in the PI3K/Akt signaling pathway via qPCR. Results revealed that in addition to monosaccharides such as glucose and fructose, the contents of polysaccharides, maltose, trehalose, and sorbitol varied significantly at different stages and states of the eggs. The expression profiles of the genes were low but increased in instant acid-soaked and RBCAS eggs before hatching. Western blot analysis results showed that the ratio of phosphorylated Akt in diapause and RBCAS eggs was equivalent but significantly higher in RBCAS eggs after activation of the PI3K/Akt signaling pathway. These findings revealed that saccharides are basic energy sources, and that the activation of the PI3K/Akt signaling pathway plays an important role during acid soaking to prevent or break diapause in eggs.