Identification And Difference Analysis Of Chemosensory Genes In The Asian Citrus Psyllid, Diaphorina Citri

The Asian citrus psyllid, Diaphorina citri is the principal vector of the highly destructive citrus disease called HuangLongBing(HLB) or citrus greening, which is a major threat to citrus cultivation worldwide. Effective pest control strategies against this pest can be better developed by identifying potential chemosensory proteins as molecular targets to develop attractants or repellents. However, the molecular basis of olfaction in the Asian citrus psyllid is not completely understood. Therefore, we performed this study to analyze the antennal and abdominal transcriptome of the Asian citrus psyllid.We identified a large number of chemoreception-related gene families and compared their expression in male and female adult antennae and terminal abdomen. Among them were genes encoding 9 odorant binding proteins(OBPs), 12 chemosensory proteins(CSPs), 46 odorant receptors(ORs), 20 gustatory receptors(GRs), 35 ionotropic receptors(IRs), 4 sensory neuron membrane proteins(SNMPs) and four different odorant-degrading enzymes(ODEs): 80 cytochrome P450 s, 12 esterases, 5 aldehyde dehydrogenases, and 1 carboxylesterase in the antennal and abdominal transcriptomes.We then mapped Illumina-sequenced transcriptome reads to unigenes to explore gene expression in male and female antennae and terminal abdominal segments. Our results revealed that a large proportion of chemosensory genes exhibited no distinct difference in their expression pattern in the antennae and terminal abdominal tissues. However, RNA-seq and RT-qPCR showed that the following chemosensory genes had significantly higher expression in antennae than terminal abdominal tissues; 4 DcitOBPs, 4 Dcit CSPs,4 Dcit IRs, 1 DcitSNMPs and 2 DcitCYPs. One DcitCYP had higher expression in the terminal abdominal tissues.Our findings showed that a large number of the chemosensory genes in the Asian citrus psyllid antennae and abdomen have sex- and tissue-specific expression profiles. These results provide the first insights into the molecular basis of chemoreception in this insect pest. Further studies on the identified differentially expressed genes would facilitate the understanding of insect olfaction and their role in the interactions between olfactory system and biological processes.