Expression patterns and binding properties of three pheromone binding proteins in the diamondback moth, Plutella xyllotella.

Pheromone binding proteins (PBPs) play a key role in transporting hydrophobic sex pheromone components emitted by con-specific female across aqueous sensillar lymph to the surface of olfactory receptor neurons. A number of PBPs have been cloned, however, details of their function are still largely unknown. Here three pheromone binding protein genes in the diamondback moth, Plutella xyllotella were cloned. The three PxylPBP genes are not only expressed in chemosensory tissues but also expressed in female reproductive organs and male legs. To better understand the functions of PxylPBPs in the initial steps of pheromone recognition, three PxylPBPs were expressed in Escherichia coli and the ligand-binding specificities of purified recombinant PBPs were investigated. Fluorescence binding assays indicate that three PxylPBPs not only robustly bound all four sex pheromone components but also significantly bound pheromone analogs with at least one double bond, while weakly bound tested plant volatiles. Although pheromone analogs bound PBPs, they could not elicit the moth's electrophysiological response. These experiments provide evidence that PxylPBPs have limited selectivity of pheromone components and analogs and some downstream components such as odor receptors might be involved in selectivity and specificity of pheromone perception in P. xyllotella.