An OBP gene highly expressed in non-chemosensory tissues affects the phototaxis and reproduction of Spodoptera frugiperda

Insect odorant binding proteins (OBPs) were initially regarded as carriers of the odorants involved in chemosensation. However, it had been observed that a growing number of OBP genes exhibited broad expression patterns beyond chemosensory tissues. Here, an OBP gene (OBP31) was found to be highly expressed in the larval ventral nerve cord, adult brain and male reproductive organ of Spodoptera frugiperda. An OBP31 knockout strain (OBP31^−/−) was generated by CRISPR/Cas9 mutagenesis. For OBP31^−/−, the larvae needed longer time to pupate, but there was no difference in the pupal weight between OBP31^−/− and wild type (WT). OBP31^−/− larvae showed stronger phototaxis than the WT larvae, indicating the importance of OBP31 in light perception. For mating rhythm of adults, OBP31^−/− moths displayed an earlier second mating peak. In the cross-pairing of OBP31^−/− and WT moths, the mating duration was longer, and hatchability was lower in OBP31^−/− group and OBP31^+/−♂ group than that in the WT group. These results suggested that OBP31 played a vital role in larval light perception and male reproductive process and could provide valuable insights into understanding the biological functions of OBPs that were not specific in chemosensory tissues.