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Spodoptera frugiperda (J.E. Smith) is a crucial agricultural pest owing to its global impact on >300 crops. Among these, the corn strain of S. frugiperda causes significant damage to maize (Zea mays L.). However, limited research exists on the influence of maize nutrients on the metamorphosis of S. frugiperda and the underlying mechanisms. In this study, the effects of different growth stages of maize leaves, namely, tender leaves (tender) and mature leaves (mature), on various aspects of larval development, including body weight, body length, developmental age, pupation rate, and eclosion rate, were investigated. Additionally, we measured the levels of 20-hydroxyecdysone (20E) and three types of juvenile hormone (JH; i.e., JH I–III) in S. frugiperda larvae fed on tender or mature. The results revealed that larvae fed on Tender exhibited significantly prolonged instar duration, reduced body weight and length, and decreased pupation and eclosion rates, with the emergence of abnormal adults. Analysis of nutritional components in maize leaves revealed significantly higher levels of amino acids, soluble sugars, and sterols in mature than in tender. Hormone analysis in S. frugiperda larvae revealed higher 20E titers in individuals feeding on mature during prepupal and pupal stages. We demonstrated the crucial role of sterols in regulating the level of 20E and pupation rate of S. frugiperda. Based on these findings, we propose that isoleucine, arginine, glutamic acid, sucrose, campesterol, and β-sitosterol serve as key nutrients influencing the development of S. frugiperda. Moreover, β-sitosterol is a significant factor influencing the interaction between maize leaves and S. frugiperda. Our research results provide a reference for the control strategy of S. frugiperda based on breeding insect-resistant varieties by altering host nutrition. [ABSTRACT FROM AUTHOR]

[Display omitted] • Establishment of an UPLC-MS/MS method for the metabolism of chlorantraniliprole in Spodoptera frugiperda. • CYP337B5 accelerates the degradation of chlorantraniliprole in S. frugiperda while JH I and JH II are greatly enhanced. • CYP337B5 is overexpressed in female adults of S. frugiperda with high JH I and JH II titers. • CYP337B5 has the homology of exogenous metabolism and endogenous synthesis. Cytochrome P450 monooxygenase (P450) has been shown to be involved in the detoxification metabolism of exogenous drugs or regulates the endogenous synthesis of juvenile hormone III (JH III). However, it is not yet known whether a particular P450 gene involved in the metabolism also affects the synthesis of juvenile hormones. Fall armyworm (FAW, Spodoptera frugiperda) showed a significant increase in juvenile hormone I (JH I) and juvenile hormone II (JH II) under chlorantraniliprole stress, and 11 chlorantraniliprole resistance-related P450 genes were significantly up-regulated. Among them, CYP337B5 was not only overexpressed in the midgut and head of FAW larvae, but also significantly increased in the female and male adult stages with high JH I and JH II titers. Injecting double-stranded RNA significantly reduced the metabolism rate of chlorantraniliprole in FAW and inhibited the production of juvenile hormones. Additionally, the degradation rates of chlorantraniliprole were significantly increased along with the production of various metabolites when incubated in vitro using recombinant CYP337B5; and JH I and JH II were also increased to some extent by 1.2 and 0.5 times. The results show that CYP337B5 is efficiently involved in the metabolism of chlorantraniliprole and specifically involved in the synthesis of JH I and JH II. We show that some P450s may have dual functions of endogenous hormone synthesis and exogenous substance metabolism in insects, which may be the root cause of the cost of drug resistance in insects. [ABSTRACT FROM AUTHOR]

Allatostatin (AS) or Allatotropin (AT) is a class of insect short neuropeptide F (sNPF) that affects insect growth and development by inhibiting or promote the synthesis of juvenile hormone (JH) in different insects. III-2 is a novel sNPF analog derived from a group of nitroaromatic groups connected by different amino acids. In this study, we found that III-2 showed high insecticidal activity against S. frugiperda larvae with a LC 50 of 18.7 mg L−1. As demonstrated by ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS), III-2 particularly facilitated JH III and hindered 20E synthesis in S. frugiperda. The results of RNA-Seq and quantitative real-time polymerase chain reaction (qPCR) showed that III-2 treatment promoted the expression of key genes such as SfCYP15C1 in JH synthesis pathway and inhibited the expression of SfCYP314A1 and other genes in the 20E synthetic pathway. Significant differences were also observed in the expression of the genes related to cuticle formation. We report for the first time that sNPF compounds specifically interfere with the synthesis and secretion of a certain JH in insects, thus affecting the ecdysis and growth of insects, and leading to death. This study may provide a new plant conservation concept for us to seek the targeted control of certain insects based on specific interference with different JH. [Display omitted] • A short neuropeptide F (sNPF) analog III-2 has good insecticidal activity against S. frugiperda. • III-2 specifically promote the synthesis of JH III, but has no effect on the titers of JH I and JH II. • III-2 inhibited the synthesis of 20E in S. frugiperda. • It lays a theoretical foundation for the development of sNPF related JH targeted insecticides. [ABSTRACT FROM AUTHOR]