Identification and analysis of odorant-binding protein genes from the wolf spider Pardosa pseudoannulata (Araneae: Lycosidae) based on its transcriptome

Abstract

Pardosa pseudoannulata, one of the dominant predators in the paddy ecosystem, is a potential resource in the biological control of rice pests. Olfaction is crucial for insect behaviors such as feeding, mating and foraging, and odorant-binding proteins (OBPs) play a vital role in smell sensing, so we suppose that OBPs may be also important in spider behaviors. In this study, we identified two putative OBP genes and obtained their complete cDNA sequences. PpseOBP1 is 842 bp long and encodes a 188 amino acids protein. PpseOBP2 is 996 bp long and encodes a 213 amino acids protein. By our predictions and analysis, both of the PpseOBPs share some similar physicochemical and structural characteristics with insect classic OBP genes, but they do not strictly observe the cysteine pattern of OBPs in insects, in which there are three amino acid residues between the second and the third cysteine residues but 27 amino acid residues in P. pseudoannulata. Phylogenetic analysis showed that two PpseOBPs clustered together at the edge of the tree, indicating their distant relationship with insects. Regarding insects, PpseOBPs were most closely related to the Periplaneta americana OBP1. Both PpseOBPs are mainly expressed in appendages (pedipalps and legs). Expression of PpseOBP1 was significantly higher in female appendages than in male appendages, while PpseOBP2 showed an extreme expression level in male pedipalps. This is the first report of molecular characterization and expression patterns of OBPs in Lycosidae and will establish a foundation for better understanding of molecular mechanisms of P. pseudoannulata olfaction and facilitate its function in biological control.