Octopamine terminates sex pheromone biosynthesis by suppressing PBAN signal in moths

Abstract

The biosynthesis and termination of insect sex pheromones should be accurately regulated. In most moths, the biosynthesis and release of sex pheromones are regulated by a class of neuropeptides known as pheromone biosynthesis activating neuropeptides (PBANs). However, endogenous mechanisms underlying the termination of sex pheromone biosynthesis in moths remain elusive. In the present study, Helicoverpa armigera was employed as a model to investigate the role of octopamine (OA) in the inhibition of sex pheromone biosynthesis. Results demonstrated that the release of sex pheromones decreased with an increase in OA titres in older female moths. Moreover, OA treatment led to a significant decrease in sex pheromone production, female capability to attract male counterparts and subsequent female acceptance, indicating its inhibitory role in sex pheromone release. Subsequent qPCR and RNAi analyses revealed that OctβR was a key receptor of OA that regulated sex pheromone biosynthesis. In addition, the OA/OctβR signal suppressed intracellular Ca2+ levels and attenuated PBAN‐mediated increase in the enzyme activities of calcineurin and acetyl‐CoA carboxylase as demonstrated by OA treatment and OctβR‐RNAi. Altogether, these results revealed a mechanism underlying the inhibition of sex pheromone production by OA via suppression of PBAN signalling in moths.

Knockout of tyramine receptor 1 results in a decrease of oviposition, mating, and sex pheromone biosynthesis in female Plutella xylostella

“…A recent study revealed that OA/Oct⊎2 could terminate the biosynthesis of sex pheromone by suppressing the PBAN signal in Helicoverpa armigera. 44 The transcription of mRNA for the PxTAR1 gene in the sex pheromone gland was significantly lower than that of the PxOct⊎2 gene (Fig. S5).…”

“…45 Therefore, it can be inferred that the sex pheromone biosynthesis in the P. xylostella pheromone gland may also be mainly terminated by OA/Oct⊎2 rather than TA/TAR1. 44 This may be the reason why PxTAR1 knockout has a different effect from TA treatment on the pheromone gland. Moreover, consistent with our previous report, 18 the mRNA level of PxTAR1 was significantly higher in the head than in the reproduction system (Fig.…”

“…Besides, TA could be converted into OA in vivo 45 . Therefore, it can be inferred that the sex pheromone biosynthesis in the P. xylostella pheromone gland may also be mainly terminated by OA/Octβ2 rather than TA/TAR1 44 . This may be the reason why PxTAR1 knockout has a different effect from TA treatment on the pheromone gland.…”