Suppression of glycerol biosynthesis-related genes decreases the effect of rapid cold hardening in Helicoverpa assulta

Abstract

Insects acquire cold hardiness for survival during the winter by increasing cryoprotectants concentration such as glycerol and trehalose after induction of rapid cold hardening (RCH). The oriental tobacco budworm, Helicoverpa assulta, is a freeze-tolerant species which increases glycerol level in the hemolymph after RCH induction. In this study, we identified two glycerol biosynthesis-related genes, glycerol-3-phosphate dehydrogenase (Has-GPDH) and glycerol kinase (Has-GK) in the fat body of H. assulta larvae. Has-GPDH harbored a conserved NAD+-dependent glycerol-3-phosphate dehydrogenase signature sequence, and Has-GK harbored two conserved FGGY carbohydrate kinase signature sequences. Phylogenetic analysis revealed both Has-GPDH and Has-GK were relatively close to those of Helicoverpa armigera. The expression levels of Has-GPDH and Has-GK were increased after RCH induction at 4°C for 6 h. After suppression of Has-GPDH and Has-GK by RNA interference, the survival rate of H. assulta at −10°C was much lower than the control after RCH induction. These results suggest that glycerol biosynthesized by Has-GPDH and Has-GK plays a crucial role in RCH-induced cold tolerance in H. assulta.