Nuclear receptor ecdysone‐induced protein 75 is required for larval–pupal metamorphosis in the Colorado potato beetle Leptinotarsa decemlineata (Say). Issue 1 (6th November 2015)

• Record Type: Journal Article
• Authors: Guo, W.‐C.; Liu, X.‐P.; Fu, K.‐Y.; Shi, J.‐F.; Lü, F.‐G.; Li, G.‐Q.
• Is Part Of: Insect molecular biology. Volume 25:Issue 1(2016:Feb.)
• Page Start: 44
• Page End: 57
• Publication Date: 2015-11-06
• Subjects: Leptinotarsa decemlineata -- E75 -- 20‐hydroxyecdysone -- juvenile hormone -- development arrest; Insects -- Molecular aspects -- Periodicals; 595.7
• DOI: 10.1111/imb.12197
• Languages: English
• ISSNs: 0962-1075

Abstract

Abstract: 20‐hydroxyecdysone (20E) and juvenile hormone (JH) are key regulators of insect development. In this study, three Leptinotarsa decemlineata Ecdysone‐induced protein 75 ( LdE75 ) cDNAs ( LdE75A, B and C ) were cloned from L. decemlineata . The three LdE75 isoforms were highly expressed just before or right after each moult. Within the fourth larval instar, they showed a small rise and a big peak 40 and 80 h after ecdysis. The expression peaks of the three LdE75 s coincided with the peaks of circulating 20E levels. In vitro midgut culture and in vivo bioassay revealed that 20E and an ecdysteroid agonist halofenozide (Hal) enhanced LdE75 expression in the day 1 final larval instars. Conversely, a decrease in 20E by feeding a double‐stranded RNA (dsRNA) against an ecdysteroidogenesis gene, Shade (LdSHD), repressed the expression of LdE75 . Moreover, Hal upregulated the expression of the three LdE75 s in LdSHD ‐silenced larvae. Thus, 20E pulses activate the transcription of LdE75 s. Furthermore, ingesting ds E75‐ 1 and ds E75‐ 2 from a common fragment of the three isoforms successfully knocked down these LdE75 s, and caused developmental arrest. Finally, knocking down LdE75 s significantly repressed the transcription of three ecdysteroidogenesis genes, lowered the 20E titre and affected the expression of two 20E‐response genes. Silencing LdE75 s also induced the expression of a JH biosynthesis gene, increased JH titre and activated the transcription of a JH early‐inducible gene. Thus, Ld E75s are required for larval–pupal metamorphosis and act mainly by modulating 20E and JH titres and mediating their signalling pathways.