Key role of juvenile hormone in controlling reproductive diapause in females of the Asian lady beetle Harmonia axyridis

Abstract

BACKGROUND The Asian lady beetle Harmonia axyridis is an important predator of several agricultural pests, including aphids and whiteflies, and thus can contribute to pest management. Commercial viability as a pest control method requires that the beetle can be mass‐reared, and that workable conditions for extended shelf‐life can be guaranteed. One of the features of Harmonia's life cycle is that it enters diapause in the adult stage when the length of the photophase starts shortening in late summer. Reduction of juvenile hormone (JH) titer has been demonstrated to be the common endocrine mechanism inducing reproductive diapause in insects. However, whether H. axyridis enters diapause dependent on JH shutdown and how the JH level is regulated before diapause remains unknown. RESULTS Like in other insects, the absence of JH triggers the induction and maintenance of reproductive diapause in H. axyridis, indicated by JH measurements and the knockdown of an intracellular JH receptor methoprene‐tolerant (Met). Methoprene, a JH analog, significantly reversed diapause into reproduction via Met. Combined with RNA‐sequencing and RNA interference, we also demonstrated that JH biosynthesis rather than the JH degradation pathway determines the reduction of JH titer in diapausing females. CONCLUSION Our results reveal the vital role of JH in regulating reproductive diapause in female H. axyridis. Harmonia axyridis diapause could thus be manipulated by targeting JH production and JH signaling. © 2021 Society of Chemical Industry.

Enhanced Degradation of Juvenile Hormone Promotes Reproductive Diapause in the Predatory Ladybeetle Coccinella Septempunctata

“…There is also some evidence that JH degradation has a role in regulating diapause. In C. bowringi and H. axyridis, JH degradation facilitates lipid storage and stress tolerance during diapause preparation (Guo et al, 2019;Gao et al, 2021). In addition, a previous study from our lab indicated that the transcript abundances of the genes encoding JHE and JHEH were both significantly increased in early diapause and decreased after diapause termination in female adults of C. septempunctata (Qi et al, 2015).…”

“…JH in the hemolymph and the tissues is mainly degraded by three enzymes, including JH esterase (JHE), JH epoxide hydrolase (JHEH) and JH diol kinase (JHDK) (Zhang et al, 2005) (Supplementary Figure S1). In many instances of reproductive diapause, a marked downregulation of genes encoding enzymes involved in JH biosynthesis is accompanied with the upregulation of genes involved in JH metabolism, suggesting that the JH titers during diapause are collaboratively regulated by the JH biosynthesis and degradation pathways (Chen H. et al, 2021;Ma et al, 2021a;Gao et al, 2021;Wu et al, 2021).…”

“…The shutdown of JH biosynthesis has been demonstrated to be critical in triggering the initiation of reproductive diapause in several species, including Colaphellus bowringi, Harmonia axyridis, and Culex pipiens (Sim et al, 2015;Gao et al, 2021;Tian et al, 2021). There is also some evidence that JH degradation has a role in regulating diapause.…”

CYP314A1‐dependent 20‐hydroxyecdysone biosynthesis is involved in regulating the development of pupal diapause and energy metabolism in the Chinese citrus fruit fly, Bactrocera minax

“…13,14 Many previous studies have revealed that juvenile hormone (JH) and 20E signaling pathways participate in the regulation of diapause. [14][15][16][17][18][19][20] The reduction of JH titer triggers female reproductive diapause in Harmonia axyridis, 21 and JH regulates reproductive diapause via the methoprene-tolerant (Met) gene in male H. axyridis. 22 Similar results also have been found in female Colaphellus bowringi.…”

Juvenile Hormone Synthesis Pathway Gene SfIPPI Regulates Sogatella furcifera Reproduction

“…The juvenile hormone (JH) is a sesquiterpenoid compound synthesized in the corpora allata of insects [1,2]. It is essential for regulating the physiological processes of insect growth, metamorphosis, reproduction, and immunity [3][4][5][6][7][8]. JH biosynthesis is associated with the expression of most JH biosynthetic enzymes in the corpora allata [9].…”