JH degradation pathway participates in hormonal regulation of larval development of Bombyx mori following λ-cyhalothrin exposure.

λ-Cyhalothrin (λ-cyh), a widely utilized pyrethroid insecticide, poses serious threats to non-target organisms due to its persistence nature in the environment. Exposure to low concentrations of λ-cyh has been observed to result in prolonged larval development in Bombyx mori, leading to substantial financial losses in sericulture. The present study was undertaken to elucidate the underlying mechanisms for prolonged development caused by λ-cyh (LC ₁₀ ) exposure. The results showed that the JH Ⅲ titer was significantly increased at 24 h of λ-cyh exposure, and the JH interacting genes Methoprene-tolerant 2, Steroid Receptor Co-activator, Krüppel-homolog 1, and JH binding proteins were also up-regulated. Although the target of rapamycin (Tor) genes were induced by λ-cyh, the biosynthesis of JH in the corpora allata was not promoted. Notably, 13 JH degradation genes were found to be significantly down-regulated in the midgut of B. mori. The mRNA levels and enzyme activity assays indicated that λ-cyh had inhibitory effects on JH esterase, JH epoxide hydrolase, and JH diol kinase (JHDK). Furthermore, the suppression of JHDK (KWMTBOMO01580) was further confirmed by both western blot and immunohistochemistry. This study has offered a comprehensive perspective on the mechanisms underlying the prolonged development caused by insecticides, and our results also hold significant implications for the safe production of sericulture.
Competing Interests: Declaration of competing interest The authors declare the following financial interests/personal relationships which may be considered as potential competing interests: Haina Sun, Bing Li reports financial support was provided by National Natural Science Foundation of China. Bing Li reports financial support was provided by Earmarked Fund for China Agriculture Research System. Haina Sun reports financial support was provided by Natural Science Foundation of Jiangsu Province. Haina Sun reports financial support was provided by Science & Technology Support Program of Suzhou. Bing Li reports financial support was provided by Natural Science Foundation of the Jiangsu Higher Education Institutions of China. Bing Li reports financial support was provided by Jiangsu Agriculture Science and Technology Innovation Fund. Yixin Dai, Xinyu Liu reports financial support was provided by 25th College Student Extracurricular Academic Research Fund of Soochow University. Bing Li reports financial support was provided by Priority Academic Program Development of Jiangsu Higher Education Institutions.
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