Functional Characterization of an Odorant Receptor Expressed in Newly Hatched Larvae of Fall Armyworm Spodoptera frugiperda.

Simple Summary: Odorant receptors (ORs) are essential to insects' highly efficient and sensitive olfactory system. ORs' stage-specific expression and precise functionality significantly influence insect behavior exhibited during particular developmental stages. Despite larvae possessing a relatively simplistic olfactory system with fewer expressed ORs than adult moths, larvae effectively employ ORs to navigate larval-specific survival challenges. This study investigated the OR SfruOR40 in newly hatched larvae of Spodoptera frugiperda, an invasive agricultural pest also known as the fall armyworm. Subsequent functional characterization indicated that SfruOR40 facilitates the detection of host plant volatiles. Our findings enhance understanding of the olfactory perception mechanisms in S. frugiperda and underscore the significance of OR expression in newly hatched larvae. In the past decade, Spodoptera frugiperda has emerged as a significant invasive pest globally, posing a serious threat to agriculture due to its broad diet, migratory behavior, and ability to cause extensive plant damage. While extensive research has focused on the olfactory capabilities of adult S. frugiperda, understanding of the olfactory process in larvae remains limited, despite larvae playing a crucial role in crop damage. To address this gap, we identified an odorant receptor (OR), SfruOR40, expressed in the first-instar larvae through phylogenetic analysis. Using quantitative real-time PCR, we compared SfruOR40 expression levels in larvae and adults. We then characterized the function of SfruOR40 against 67 compounds using the Xenopus oocyte expression system and found that SfruOR40 responded to three plant volatiles. Further, behavioral experiments revealed a larval attraction to (−)-trans-Caryophyllene oxide. This study elucidates SfruOR40's role in the olfactory recognition of newly hatched S. frugiperda larvae, expanding our knowledge of such mechanisms in Noctuid moths. Furthermore, it highlights the potential of plant-derived natural products for biological pest control from a behavioral ecology perspective. [ABSTRACT FROM AUTHOR]