Ecdysis triggering hormone is essential for larva–pupa–adult transformation in Leptinotarsa decemlineata

Abstract

In Drosophila melanogaster, ecdysis triggering hormone (ETH) is the key factor triggering ecdysis behaviour and promoting trachea clearance. However, whether ETH plays the dual roles in non‐dipteran insects is unknown. In this survey, we found that Ldeth mRNA levels were positively correlated with circulating 20‐hydroxyecdysone (20E) titers in Leptinotarsa decemlineata. Ingestion of an ecdysteroid agonist halofenozide or 20E stimulated the transcription of Ldeth, whereas RNA interference (RNAi) of ecdysteroidogenesis (LdPTTH or LdSHD) or 20E signalling (LdEcR, LdUSP or LdFTZ‐F1) genes inhibited the expression, indicating ETH acts downstream of 20E. RNAi of Ldeth at the final instar stage impaired pupation. More than 80% of the Ldeth‐depleted beetles remained as prepupae, completely wrapped in the old larval cuticles. These prepupae became withered, dried and darkened gradually, and finally died in soil. The remaining Ldeth hypomorphs pupated and emerged as abnormal adults, bearing smaller and wrinkle elytrum and hindwing. Moreover, the tracheae in the Ldeth hypomorphs were full of liquid. We accordingly proposed that the failure of trachea clearance disenabled air‐swallowing after pupa–adult ecdysis and impacted wing expansion. Our results suggest that ETH plays the dual roles, initiation of ecdysis and motivation of trachea clearance, in a coleopteran.

Ecdysis Triggering Hormone, Eclosion Hormone, and Crustacean Cardioactive Peptide Play Essential but Different Roles in the Molting Process of Mud Crab, Scylla paramamosain

“…In insects such as Leptinotarsa decemlineata and Bactrocera dorsalis, ETH is mainly produced by Inka epithelial cells of the endotracheal gland in the trachea. The ETH expression level is the highest at the late premolt stage (Shi et al, 2017;Shen et al, 2021). In Drosophila, EH is expressed in the neuronal tissues and trachea, which participate in the regulation of molting behaviors (Scott et al, 2020).…”

“…Even the initiation of the molting process has started, there is no guarantee that the animal will molt successfully as the fulfillment of the subsequent events must be straightly followed. In insects, neuropeptides that induce molting behavior include ecdysis-triggering hormone (ETH) (Shi et al, 2019a;Minh Nhut et al, 2020;Shen et al, 2021), eclosion hormone (EH) (Hull et al, 2009;Zhou et al, 2017;Scott et al, 2020), crustacean cardioactive peptide (CCAP) (Veelaert et al, 1997;Arakane et al, 2008;Jackson et al, 2009), etc.…”

“…In this study, we have monitored the expression of several key molting-related genes ETH, EH and CCAP that induce the molting process the crab (Fort et al, 2007;Hull et al, 2009;Shen et al, 2021). Also, we have developed in vivo assays in juvenile crabs during the premolt stage of the molting crab.…”

RNA interference targeting Ras GTPase gene Ran causes larval and adult lethality in Leptinotarsa decemlineata

“…All dsRNAs were generated by Escherichia coli HT115 (DE3) competent cells lacking RNase III following the established method. 10,11 The bacterial solutions (at a dsRNA concentration of about 0.5 μg/mL) were used for the experiment.…”

Transcriptome responses of RNAi-mediated ETH knockdown in Scylla paramamosain at different premolt substages

“…Researchers have found that ETH has additional roles besides initiating ecdysis. In insects, ETH plays dual roles, initiation of ecdysis and trachea clearance ( 11 , 12 ). In Drosophila , the knockdown of ecdysis triggering hormone receptor ( ETHR ) revealed differential expression of genes involved in axon guidance, courtship behavior, and chemosensory functions, which indicated a role in the regulation of courtship behavior ( 13 ).…”