Molecular cloning and functional identification of an insect odorant receptor gene in Spodoptera litura (F.) for the botanical insecticide rhodojaponin III

Specific behaviors of insects are stimulated by the recognition of chemicals in the external environment by sensilla on chemoreceptive organs. Rhodojaponin III is a nonvolatile natural botanical insecticide, which has an intense effect of deterring oviposition activity against many insects. This study aimed to determine whether the Or83b protein is involved in the recognition of rhodojaponin III. The SlOr83b protein has a conserved seven-transmembrane domain and a putative receptor/receptor interaction loop. The Or83b mRNA is first transcribed in 1st larvae, and expressed in later larval stages. A high level of Or83b mRNA is expressed in pupal and adult stages. Knockdown of SlOr83b expression was achieved through RNAi by injecting double-stranded RNA (dsRNA) into the 8th day pupae, and oviposition significantly increased on rhodojaponin III treated cabbage leaves. These results suggest that Or83b is critical for insects to identify the nonvolatile the insecticide rhodojaponin III.