Transcriptomic analysis reveals that high-protein artificial diet enhances reproductive performance of Protaetia brevitarsis (Lewis) (Coleoptera: Scarabaeidae).

Insects have emerged as promising sustainable alternative protein sources, among which Protaetia brevitarsis (Lewis) (Coleoptera: Scarabaeidae) exhibits considerable potential for valorizing lignocellulosic wastes (e.g. crop straw) into high-value proteins. The larvae of this species are traditionally used in medicine and as a health food, but the underdeveloped rearing technology for adults has impeded large‑scale commercialization and application. Thus, the development and optimization of artificial diets represent a critical breakthrough for overcoming this bottleneck. Herein, we integrated expression profile analysis to investigate the molecular mechanisms underlying nutritional digestion in P. brevitarsis and the regulatory effects of different diets on its growth and reproductive performance. Transcriptomic analyses further unveiled the core nutritional metabolic traits of P. brevitarsis: the larval midgut exhibited broad and high-level expression of genes involved in carbohydrate, fat, and vitamin digestion and absorption, supporting active metabolism of multiple nutrients; in contrast, adults displayed a pronounced demand for proteins. Notably, although adult intestines exhibited fewer total expressed genes, the protein digestion and absorption pathway was exceptionally active, highlighted by 7 core protease genes each displaying a Fragments Per Kilobase of transcript per Million mapped reads value exceeding 10,000. This pattern underscores the high protein demand of adults, laying a robust theoretical foundation for the artificial rearing of P. brevitarsis and the precise formulation of artificial diets. Feeding trials demonstrated that adults fed a high-protein artificial diet exhibited significantly increased body weight from the third week post-feeding, with cumulative egg production 1.62-fold higher than that of the apple-fed control group. Furthermore, this study provides valuable insights for the development of artificial diets for economically important insects and the sustainable advancement of the insect rearing industry, ultimately contributing to mitigating global protein demand pressures.