Identification of a hypertrehalosemic factor in Spodoptera exigua

Abstract

Trehalose is a major blood sugar in insects with a range of physiological functions, including an energy source and a cryoprotectant. Hemolymph trehalose concentrations are tightly regulated according to physiological conditions. An insulin-like peptide, SeILP1, downregulates hemolymph trehalose concentrations in Spodoptera exigua. Here, we identified a factor that upregulates hemolymph trehalose concentration in S. exigua. Hemolymph trehalose concentrations were significantly increased after immune challenge or under starvation in a time-dependent manner. To determine endocrine factors responsible for the upregulation, stress-associated mediators, such as octopamine, serotonin, or eicosanoids were injected, but they did not upregulate hemolymph trehalose. On the other hand, injection with Schistocerca gregaria adipokinetic hormone (AKH) significantly increased hemolymph trehalose concentration in S. exigua. During upregulation of hemolymph trehalose by AKH injection, trehalose degradation appeared to be inhibited because expression of trehalase and SeILP1 were significantly suppressed while that of trehalose phosphate synthase was not significantly changed. Interrogation of a Spodoptera genome database identified an S. exigua AKH-like gene and its expression was confirmed. During starvation, its expression concentrations were increased, although RNA interference specific to the AKH-like hypertrehalosemic factor (SeHTF) gene significantly prevented the upregulation of hemolymph trehalose concentrations during starvation. A synthetic peptide of SeHTF was prepared and injected into S. exigua larvae. At nanomolar concentration, the synthetic SeHTF peptide effectively upregulated hemolymph trehalose concentrations. Here we report a novel hypertrehalosemic factor in S. exigua (SeHTF).

Invertebrate Trehalose-6-Phosphate Synthase Gene: Genetic Architecture, Biochemistry, Physiological Function, and Potential Applications

“…Anastrepha ludens larvae developed a protection mechanism based on the synthesis of trehalose by TPS to achieve greater survivability to stress caused by hydrostatic pressure (Vargas-Ortiz et al, 2013 ). Starvation and the injection of dsSeHTF—an Akh-like hypertrehalosemic factor—can significantly decrease TPS expression level (Park and Kim, 2017 ). Although no conspicuous phenotype changes were observed after TRE and TPS genes were silenced individually or simultaneously in the nematode A. besseyi , its survival under hypertonic osmotic pressure decreased significantly and the recovery was delayed.…”

The Molecular Characterization and Gene Expressions of Trehalase in Bumblebee, Bombus lantschouensis (Hymenoptera: Apidae)

“…A high temperature not only breaks the moisture balance of the internal environment and interferes with normal metabolism but it also causes body temperature to rise and affects enzyme activity and protein function in insects (Du et al, 2007). Previous studies showed that trehalase optimizes temperature in the range of 40-65°C (Zou et al, 2013;Shukla et al, 2014;Youngjin & Yonggyun, 2017). At a high temperature, the parasitic nematode Aphelenchoides besseyi improves its resistance by upregulating the trehalase gene (Chen et al, 2016).…”

“…Trehalose is a feedback-regulating substance involved in the feeding behavior and nutrient intake of insects (Wyatt, 1967). Trehalose provides energy when insects are starving; thus, it has a role in the regulation of insect functions under starvation conditions (Tang et al, 2014;Youngjin & Yonggyun, 2017). In H. axyridis adults, the stored food reserves can provide energy to sustain vital activities for 8 h, but energy limitations have a direct impact on the desire to find food (Tang et al, 2014).…”

Toll/IMD signal pathways mediate cellular immune responses via induction of intracellular PLA2 expression

“…Immature development of insects depends on trehalose availability (Matsuda, Yamada, Yoshida, & Nishimura, ). Its hemolymph titers in S. exigua are tightly regulated by insulin‐like peptide and hypertrehalosemic hormone (HTH; Kim & Hong, ; Park & Kim, ). Sun and Steele () have reported iPLA 2 ‐like activity in fat body cell extracts of American cockroach ( Periplaneta americana ).…”