Ecdysis Triggering Hormone (ETH) plays a role in the regulation of juvenile hormone synthesis in the mosquito Aedes aegypti

Juvenile hormone (JH) is a major hormonal regulator in insects. JH titer is determined by the rate at which the corpora allata (CA) synthesizes JH. The rate of CA activity is regulated by allatostatic (inhibitory) or allatotropic (stimulatory) factors. Ecdysis triggering hormone (ETH) is known for its critical role in orchestrating ecdysis, but its role in the regulation of JH synthesis is unknown. Here we describe the stimulatory effect of ETH on JH synthesis during the maturation process the CA undergoes during the last six hours before adult emergence; a time when genes encoding JH biosynthetic enzymes become transcriptionally active and the CA starts synthesizing basal levels of JH. ETH receptors (ETHr) are present in both the corpora allata  and the corpora cardiaca (CA-CC). Silencing of ETH receptors (ETHr) by RNA interference (RNAi) in pupa resulted in reduced JH synthesis in adults 24h after emergence. Our results suggest that ETH regulates JH synthesis directly through its receptors in CA as well as indirectly via the CC. We would like to propose that ETH should be included into the group of regulatory peptides controlling JH synthesis in insects.