Pharmacological Properties and Function of the PxOctβ3 Octopamine Receptor in Plutella xylostella (L.)

SIMPLE SUMMARY: The diamondback moth (Plutella xylostella) is a global migratory pest that primarily destroys cruciferous vegetables. Due to the extensive application of insecticides, P. xylostella has developed resistance to more than 90 types of active insecticidal ingredients, and this has exacerbated its control. Octopamine plays a key role in the neural activity of invertebrates because it regulates various physiological functions and behaviors in insects. The actions of octopamine have been shown to be mediated via the activation of octopamine receptors (OARs). In this study, we identified an OAR gene (PxOctβ3) in P. xylostella, analyzed its molecular characteristics and patterns of expression, and expressed it in HEK-293 cells to not only analyze the pharmacological properties of the encoded PxOctβ3 receptor but also identify its specific agonists and antagonists. RNA interference-mediated inhibition of the expression of PxOctβ3 resulted in shorter durations of pupation in the diamondback moth. These results indicate that PxOctβ3 plays an important role in the physiology of P. xylostella. ABSTRACT: The diamondback moth (Plutella xylostella) is one of the most destructive lepidopteran pests of cruciferous vegetables, and insights into regulation of its physiological processes contribute towards the development of new pesticides against it. Thus, we investigated the regulatory functions of its β-adrenergic-like octopamine receptor (PxOctβ3). The open reading frame (ORF) of PxOctβ3 was phylogenetically analyzed, and the levels of expression of the receptor mRNA were determined. This ORF was also cloned and expressed in HEK-293 cells. A series of octopamine receptor agonists and antagonists were tested against PxOctβ3. We showed that the receptor is a member of the Octβ3 protein family, and an analysis using quantitative PCR showed that it was expressed at all developmental stages of P. xylostella. Octopamine activated PxOctβ3, resulting in increased levels of intracellular cAMP. Furthermore, the agonists naphazoline, clonidine, 2-phenethylamine, and amitraz activated the PxOctβ3 receptor, and naphazoline was the most effective. Only metoclopramide and mianserin had significant antagonistic effects on PxOctβ3, whereas yohimbine, phentolamine, and chlorpromazine lacked obvious antagonistic effects. The injection of double-stranded RNA in an RNA interference assay indicated that PxOctβ3 regulates development in P. xylostella. This study demonstrated the pharmacological properties and functions of PxOctβ3 in P. xylostella, thus, providing a theoretical basis for the design of pesticides that target octopamine receptors.