Distinct microRNA and mRNA responses elicited by ecdysone, diapause hormone and a diapause hormone analog at diapause termination in pupae of the corn earworm, Helicoverpa zea

Authors: REYNOLDS, JULE - The Ohio State University; Nachman, Ronald; DENLINGER, DAVID - The Ohio State University

Submitted to: General and Comparative Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/19/2018
Publication Date: 5/15/2019
Citation: Reynolds, J.A., Nachman, R.J., Denlinger, D.L. 2019. Distinct microRNA and mRNA responses elicited by ecdysone, diapause hormone and a diapause hormone analog at diapause termination in pupae of the corn earworm, Helicoverpa zea. General and Comparative Endocrinology. 278:68-78.
DOI: https://doi.org/10.1016/j.ygcen.2018.09.013

Interpretive Summary: Insect pests have developed resistance to several conventional pesticides, and new approaches are needed for pest management. Although neuropeptides (short chains of amino acids) serve as potent messengers in insects to regulate vital functions, the neuropeptides hold little promise as pest control agents because they can be degraded in the target pest. New, selective control agents may be developed by designing mimics of these neuropeptides that resist degradation and either inhibit or over-stimulate critical neuropeptide-regulated life functions. Neuropeptides of the ‘diapause hormone’ class regulate the ability of crop pest insects to survive harsh winter conditions by entering the protective state of diapause, a type of ‘hibernation’. We report here that three distinctly different hormones or hormone mimics are capable of terminating diapause in the corn earworm, an important crop pest. A study of the mechanistic pathways initiated by these three hormonal agents reveal several common themes, though a number of the pathways chosen are unique to the specific agent used to break diapause. These discoveries indicate that different pathways and mechanisms can lead to the same final behavioral response in these pest insects and shed further light on how the process of diapause can be manipulated to their detriment. The study will aid in the design of neuropeptide-like compounds capable of disrupting the survival behaviors of these agricultural pests and lead to the development of novel control strategies.

Technical Abstract: Ecdysone, diapause hormone and a diapause hormone analog are all capable of breaking pupal diapause and prompting initiation of adult development in the cotton earworm, Helicoverpa zea. In this study we asked whether these three chemically-distinct diapause terminators elicit the same effect on expression of a collection of microRNAs and transcripts encoding components of the ecdysone signaling pathway. Injection of all three endocrine agents resulted in downregulation of one miRNA, miR-277-3p, a miRNA previously linked to the insulin/FOXO signaling pathway, and all three agents promoted upregulation of spook, a member of the ecdysone biosynthesis pathway, and iswi, an ecdysone-responsive transcript. Other miRNA and mRNA responses varied depending on the agent used to terminate diapause, thus suggesting that different endocrine pathways and mechanisms can lead to the same final developmental response.