RNA interference of glycerol biosynthesis suppresses rapid cold hardening of the beet armyworm,Spodoptera exigua

Abstract

SUMMARYThe beet armyworm, Spodoptera exigua, is a freeze-susceptible species that overwinters in temperate zones without diapause. A rapid cold hardening (RCH) and supercooling capacity usually play crucial roles in survival during the overwintering period. This study identified a cryoprotectant as a RCH factor of S. exigua. Pre-exposure of S. exigua larvae to 4°C significantly increased survival at −10°C in all developmental stages from egg to adult. RCH was dependent on the duration of the pre-exposure period. RCH also significantly enhanced the supercooling capacity. Cryoprotectant analysis using HPLC showed that the pre-exposure treatment allowed the larvae to accumulate glycerol in the hemolymph. Two genes, glycerol-3-phosphate dehydrogenase (GPDH) and glycerol kinase (GK), were identified as being associated with glycerol biosynthesis, and were cloned from S. exigua larvae. Both GPDH and GK were expressed in all developmental stages of S. exigua. RNA interference (RNAi) of either GPDH or GK significantly inhibited glycerol accumulation in the hemolymph of S. exigua. Larvae treated with RNAi for GPDH or GK exhibited a significant decrease in RCH capacity. The glycerol accumulation in response to 4°C appeared to be under the control of a humoral signal, because a ligation experiment prevented glycerol accumulation in the other half of the body. This study indicates that glycerol is a RCH factor of S. exigua and its synthesis is in response to low temperature via humoral mediation. Supplementary material available online at

Regulation of hemolymph trehalose level by an insulin-like peptide through diel feeding rhythm of the beet armyworm, Spodoptera exigua

“…Sugars are primarily used for the metabolic Control (feeding) Starvation production of ATP energy and carbon source. Compared to glucose as the main blood sugar, trehalose is the principal hemolymph sugar in insects including S. exigua [41,54]. Our current study showed a fluctuation of trehalose levels in the hemolymph of S. exigua larvae in a diel rhythm according to feeding behavior.…”

“…Especially, its massive feeding activity during last instar allows the larvae to grow more than four times in body weight and gives serious economic damage to crops [30]. Its major sugar in hemolymph (= insect blood) is trehalose [41]. Like other insects to keep a constant level of hemolymph trehalose, S. exigua needs to control the fluctuating trehalose levels along with nutrient uptake from the gut to the hemolymph under a circadian feeding rhythm.…”

A Transformed Bacterium Expressing Double-Stranded RNA Specific to Integrin β1 Enhances Bt Toxin Efficacy against a Polyphagous Insect Pest, Spodoptera exigua

“…Several genes of S . exigua are modulated in their expressions by their specific dsRNA treatments and exhibit significant RNAi efficacies [ 19 – 24 ]. Moreover, oral feeding of dsRNA was effective to induce significant RNAi in S .…”

Transciptomic Analysis of Larval Fat Body of Plutella xylostella under Low Temperature

“…지방체는 척추동물의 간과 비 슷한 역할을 하며, 대사중심으로써 trehalose-6-phosphate synthase를 이용하여 trehalose를 생산한다 (Kern et al, 2012). 파밤나방에서 보고된 것처럼 (Park and Kim, 2013) * The expression level of each contig can be divided into upregulation (log 2 Fc>2), downregulation (log 2 Fc<-2), and not meaningful (-2<log 2 Fc<2), compared to the control. 2<log 2 Fc<10: ▲; 10<log 2 Fc<50: ▲▲; -10<log 2 Fc<-2: ▼; -50<log 2 Fc<-10: ▼▼ Note…”