Annotating the odorant receptors of Diaphorina citri

The Asian Citrus Psyllid (Diaphorina citri) is the vector for Candidatus liberibacter, the causative agent of Citrus Greening Disease. These insects have several different kinds of chemoreceptors, which are highly conserved among diverse insect species: odorant receptors (ORs), odorant-binding proteins (OBPs), gustatory receptors (GRs), and ionotropic receptors (IRs). Behaviors such as host-seeking, reproduction, and oviposition are influenced by the role these receptors play in chemoreception. ORs and IRs are transmembrane ion channels, whereas OBPs function as carrier proteins that deliver chemical odorants to the receptors, and the functionality of GRs is still in question. While there have been partial automatic annotations published, there is yet to be a complete catalog of any of these proteins. The automatic annotations are a helpful and occasionally necessary starting place but are often inaccurate and partial. Therefore, we are manually annotating the odorant receptors of this species using a variety of bioinformatic tools. The process begins with BLAST searching and using the Fgenesh++ genome annotation pipeline to find a region that likely contains a receptor. Crucial to ensuring the accuracy of these annotations is utilizing RNAseq data and mapping reads to contigs to identify exon coding regions. Once these annotations are complete, the information can be used within the two-electrode voltage clamp system to deorphanize receptors and determine potential chemical attractants or repellants. Ultimately, this project will aid in developing novel tools for surveillance and control of this devastating agricultural pest.