Functional Characterization of Odorant Binding Protein 27 (RproOBP27) From Rhodnius prolixus Antennae

Abstract

Olfactory proteins mediate a wide range of essential behaviors for insect survival. Odorant binding proteins (OBPs) are small soluble olfactory proteins involved in the transport of odor molecules (=odorants) through the sensillum lymph to odorant receptors, which are housed on the dendritic membrane of olfactory sensory neurons also known as olfactory receptor neurons. Thus, a better understanding of the role(s) of OBPs from <i>Rhodnius prolixus</i>, one of the main vectors of Chagas disease, may ultimately lead to new strategies for vector management. Here we aimed at functionally characterize OBPs from <i>R. prolixus</i>. Genes of interest were selected using conventional bioinformatics approaches and subsequent quantification by qPCR. We screened and estimated expression in different tissues of 17 <i>OBPs</i> from <i>R. prolixus</i> adults. These analyses showed that 11 <i>OBPs</i> were expressed in all tissues, whereas six <i>OBP</i> genes were specific to antennae. Two OBP genes, <i>RproOBP6</i> and <i>RproOBP13</i>, were expressed in both male and female antennae thus suggesting that they might be involved in the recognition of semiochemicals mediating behaviors common to both sexes, such host finding (for a blood meal). Transcripts for <i>RproOBP17</i> and <i>RproOBP21</i> were enriched in female antennae and possibly involved in the detection of oviposition attractants or other semiochemicals mediating female-specific behaviors. By contrast, <i>RproOBP26</i> and <i>RproOBP27</i> might be involved in the reception of sex pheromones given that their transcripts were highly expressed in male antennae. To test this hypothesis, we silenced <i>RproOBP27</i> using RNAi and examined the sexual behavior of the phenotype. Indeed, adult males treated with <i>dsOBP27</i> spent significantly less time close to females as compared to controls. Additionally, docking analysis suggested that RproOBP27 binds to putative sex pheromones. We therefore concluded that RproOBP27 might be a pheromone-binding protein.