Niemann-Pick proteins type C2 are identified as olfactory related genes of Pardosa pseudoannulata by transcriptome and expression profile analysis

Abstract

In arthropods, the large majority of studies on olfaction have been mainly focused on insects, whereas little on Arachnida, even though olfaction is very important in arachnid behavior. Pardosa pseudoannulata is one of the most common wandering spiders in rice fields, as the important natural enemy against a range of pests. However, little is known about the potential chemosensory proteins involved in olfactory behavior of these spiders. Niemann-Pick proteins type C2 (NPC2) as a new class of binding and transport proteins for semiochemicals in arthropods especially ticks and mites has received more attention in recent years. In this study, six NPC2s namely PpseNPC1-6 were newly identified in the appendages of P. pseudoannulata based on transcriptome data. A phylogenetic analysis indicated that all of P. pseudoannulata NPC2s were clustered together forming one clade with high posterior probability values. In addition, the sequences shared the same subclade with the NPC2 sequences of ticks and scorpion. The motif-patterns indicated that PpseNPC2-5 had the common pattern with the two-spotted spider mite Tetranychus urticae and the ant Trachymyrmex cornetzi. Furthermore, quantitative real-time PCR (qPCR) measurements were conducted to evaluate the expression profile of these genes in various tissues of P. pseudoannulata. It was found that most NPC2s (PpseNPC2-1, PpseNPC2-2, PpseNPC2-5 and PpseNPC2-6) were highly expressed in adult pedipalps and chelicerae. Owing to the functional olfactory organs in Chelicerata of pedipalps, our results supported a putative role of NPC2s as new odorant carriers in P. pseudoannulata.