Trehalose is a major blood sugar in insects. It functions as carbohydrate nutrient source to all tissues with a relatively constant level and also serves as a cryoprotectant at high levels in some insects. Thus, its hemolymph levels need to be controlled according to physiological conditions. An insulin-like peptide, SeILP1, was identified and showed to mediate down-regulation of the hemolymph trehalose levels of Spodoptera exigua larvae. This study showed that hemolymph trehalose levels of S. exigua significantly increased upon immune-challenge and under starvation in a time-dependent manner. During up-regulation of the hemolymph trehalose, the gene expression of trehalose phosphate synthase significantly increased, but that of trehalase significantly decreased. Injection of biogenic monoamines, such as octopamine and serotonin, did not increase the hemolymph trehalose levels. Either treatment of arachidonic acid or eicosanoid biosynthesis inhibitor did not change the hemolymph trehalose levels. However, injection of adipokinetic hormone (AKH) of Manduca sexta significantly increased the trehalose levels. Interrogation of Spodobase identified an AKH-like gene of S. exigua. Its expression increased with starvation in the larvae. Its RNA interference significantly prevented the up-regulation of the hemolymph trehalose levels in S. exigua.

• Yonggyun Kim(Department of Bioresource Sciences, Andong National University)
• Sungjin Kwon(Department of Bioresource Sciences, Andong National University)
• Youngjin Park(Department of Bioresource Sciences, Andong National University)