Fitness Costs of Chlorantraniliprole Resistance Related to the <i>SeNPF</i> Overexpression in the <i>Spodoptera exigua</i> (Lepidoptera: Noctuidae)

• Main Authors: Changwei Gong, Xinge Yao, Qunfang Yang, Xuegui Wang, Yuming Zhang, Yumeng Wang, Litao Shen
• Format: Article
• Language: English
• Published: MDPI AG 2021-05-01
• Series: International Journal of Molecular Sciences
• Subjects: ryanodine receptors; vitellogenin; post-mating response; mating rate; oviposition
• Online Access: https://www.mdpi.com/1422-0067/22/9/5027
• ISSN: 1661-6596; 1422-0067

<i>Spodoptera</i><i>exigua</i>, a multifeeding insect pest, has developed a high level of resistance to chlorantraniliprole, which is a benzoylurea insecticide that targets the ryanodine receptors (RyRs). Herein, the resistant strain (SE-Sel) and sensitive strain (SE-Sus) were obtained by bidirectional screening for six generations. The potential oviposited eggs and oviposition rate of the SE-Sel strain were dramatically lower than those of the SE-Sus strain; on the contrary, the weights of prepupae and preadult were significantly increased. As a post-mating response, the higher number of non-oviposited eggs in the SE-Sel strain was caused by a lower mating rate. In addition, the expression levels of <i>vitellogenin</i> (<i>SeVg</i>) and its receptor (<i>SeVgR</i>) in the SE-Sel strain were consistently lower than those in the SE-Sus strain. An RyR^I4743M mutation, contributing to the resistance to chlorantraniliprole, was located in the S3 transmembrane segments and might have affected the release of calcium ions; it led to the upregulated expression of the neuropeptide <i>SeNPF</i> and its receptor <i>SeNPFR</i>, and the mating and oviposition rate were significantly recovered when the <i>SeNPF</i> was knocked down though RNA interference (RNAi) in the male adult of the SE-Sel strain. Moreover, the expression of the juvenile hormone-binding proteins <i>SeJHBWDS3</i> and <i>SeJHBAN</i> in the male adult of the SE-Sel strain was significantly decreased, which proved the existence of a fitness cost from another angle. Therefore, these results indicate that the fitness cost accompanied by chlorantraniliprole resistance in <i>S. exigua</i> may be related to the decrease in mating desire due to <i>SeNPF</i> overexpression.