Functional characterization of β-adrenergic-like octopamine receptors in planthopper reproduction and feeding

As an essential biogenic amine in invertebrates, octopamine (OA) regulates multiple physiological and behavioral processes via binding to octopamine receptors (OARs). The small brown planthopper Laodelphax striatellus is an important agricultural pest. However, little is known about OARs in L. striatellus. Herein, three β-adrenergic-like OARs (LsOA2s) were cloned, including LsOA2B1, LsOA2B2, and LsOA2B3. LsOA2s were expressed at the highest levels in egg stage and brain. Knockdown of LsOA2s significantly decreased the transcript levels of vitellogenin (LsVg) and Vg receptor (LsVgR), and reduced LsVg protein levels. LsOA2B2 knockdown shortened the oviposition period and inhibited the fecundity, while silencing LsOA2B1 and LsOA2B3 did not affect the reproduction performance including the preoviposition period, oviposition period, and fecundity. Ovary dissection indicated that LsOA2B2 knockdown decreased the ovary area and detained eggs. In addition, LsOA2s silencing prolonged the hatching period and reduced the hatching rate, and shortened the egg length on the fifth day of development. LsOA2B2 silencing also reduced egg width. Furthermore, LsOA2s knockdown decreased honeydew excretions of adults. Overall, these results provide evidence that LsOA2s play important roles in the reproduction and feeding behaviors of L. striatellus, and offer a reference for the exploration of potential molecular targets to control planthoppers.