Metabolic changes during larval-pupal metamorphosis of Helicoverpa armigera

Energy metabolism is essential for insect metamorphosis. The accumulation and utilization of energy is still not completely clear during larval-pupal metamorphosis of holometabolous insects. We used metabolome and transcriptome analysis to reveal key metabolic changes in the fat body and plasma and the underlying metabolic regulation mechanism of Helicoverpa armigera, an important global agricultural insect pest, during larval-pupal metamorphosis. During the feeding stage, activation of aerobic glycolysis provided intermediate metabolites and energy for cell proliferation and lipid synthesis. During the non-feeding stages (the initiation of the wandering stage and the prepupal stage), aerobic glycolysis was suppressed, while, triglyceride degradation was activated in the fat body. The blocking of metabolic pathways in the fat body was probably caused by 20-hydroxyecdysone-induced cell apoptosis. 20-hydroxyecdysone cooperated with carnitine to promote the degradation of triglycerides and the accumulation of acylcarnitines in the hemolymph, allowing rapid transportation and supply of lipids from the fat body to other organs, which provided a valuable reference for revealing the metabolic regulation mechanism of lepidopteran larvae during the last instar. Carnitine and acylcarnitines are first reported to be key factors that mediate the degradation and utilization of lipids during larval-pupal metamorphosis of lepidopteran insects.

Automated summary

Energy metabolism is crucial in insect metamorphosis, particularly in the larval-pupal stage of holometabolous insects. In this study, metabolome and transcriptome analyses were conducted to elucidate the metabolic changes and regulatory mechanisms during larval-pupal metamorphosis of the cotton bollworm, Helicoverpa armigera. The findings revealed that aerobic glycolysis supported cell proliferation and lipid synthesis during the feeding stage, while triglyceride degradation and acylcarnitine accumulation were activated during non-feeding stages. This study provides valuable insights into the metabolic regulation mechanism of lepidopteran larvae during their final stage of development.