A tyramine receptor gene LsTAR2 is involved in reproduction and feeding in the small brown planthopper Laodelphax striatellus

Abstract

Tyramine (TA) is an important biogenic amine present in the central nervous system of insects, and mediates a variety of physiological and behavioral functions via tyramine receptors (TARs). However, TARs have not yet been characterized in planthoppers, and their physiological functions remain poorly understood in rice pests. Here, we cloned a tyramine receptor gene (LsTAR2) from the small brown planthopper Laodelphax striatellus, one of the most destructive rice pests. LsTAR2 shares high sequence identity with its orthologous receptors, and is closely related to its corresponding receptor groups. LsTAR2 transcript was expressed mostly in the egg stage and brain. RNAi-mediated knockdown of LsTAR2 significantly prolonged the preoviposition period and decreased the fecundity in females. Furthermore, LsTAR2 knockdown reduced the expression levels of vitellogenin (LsVg) in the fat body and ovary of L. striatellus, and changed the expressions of juvenile hormone (JH) and 20-hydroxyecdysone (20E) pathway genes. In addition, LsTAR2 knockdown significantly decreased the honeydew excretion of the adults, and affected the transcript levels of feeding-related neuropeptide signaling genes. These results provide critical information concerning the role of LsTAR2 in reproduction and feeding behavior in L. striatellus, and open the way for further investigations into novel strategies targeting TARs for pest control.