De Novo Transcriptome Identifies Olfactory Genes in Diachasmimorpha longicaudata (Ashmead).

Liangde Tang,Haiyan Zhao,Lihui Liu,Yonghao Yu,Wen Lu,Jimin Liu

doi:10.3390/genes11020144

Abstract

Diachasmimoorpha longicaudata (Ashmead, D. longicaudata) (Hymenoptera: Braconidae) is a solitary species of parasitoid wasp and widely used in integrated pest management (IPM) programs as a biological control agent in order to suppress tephritid fruit flies of economic importance. Although many studies have investigated the behaviors in the detection of their hosts, little is known of the molecular information of their chemosensory system. We assembled the first transcriptome of D. longgicaudata using transcriptome sequencing and identified 162,621 unigenes for the Ashmead insects in response to fruit flies fed with different fruits (guava, mango, and carambola). We annotated these transcripts on both the gene and protein levels by aligning them to databases (e.g., NR, NT, KEGG, GO, PFAM, UniProt/SwissProt) and prediction software (e.g., SignalP, RNAMMER, TMHMM Sever). CPC2 and MIREAP were used to predict the potential noncoding RNAs and microRNAs, respectively. Based on these annotations, we found 43, 69, 60, 689, 26 and 14 transcripts encoding odorant-binding protein (OBP), chemosensory proteins (CSPs), gustatory receptor (GR), odorant receptor (OR), odorant ionotropic receptor (IR), and sensory neuron membrane protein (SNMP), respectively. Sequence analysis identified the conserved six Cys in OBP sequences and phylogenetic analysis further supported the identification of OBPs and CSPs. Furthermore, 9 OBPs, 13 CSPs, 3 GRs, 4IRs, 25 ORs, and 4 SNMPs were differentially expressed in the insects in response to fruit flies with different scents. These results support that the olfactory genes of the parasitoid wasps were specifically expressed in response to their hosts with different scents. Our findings improve our understanding of the behaviors of insects in the detection of their hosts on the molecular level. More importantly, it provides a valuable resource for D. longicaudata research and will benefit the IPM programs and other researchers in this filed.

Highlights

Diachasmimoorpha longicaudata (Ashmead, D. longicaudata) is a solitary species of parasitoid wasp of several fruit fly species and has been introduced to many countries as a biological control agent.Its host, Bactrocera dorsalis Hendel, can attack many fruit species and some other plants, such as Caricaceae, Moraceae, Myrtaceae, Rosaceae, and Solaneaceae [1]
We identified a number of odorant-binding protein (OBP), chemosensory proteins (CSPs), odorant receptor (OR), ionotropic receptor (IR), sensory neuron membrane protein (SNMP), and gustatory receptor (GR) expressed in the Ashmead insects
We identified 43 OBPs, 69 CSPs, 60 GRs, 689 ORs, 26 IRs, and 14 SNMPs in D. longicaudata (Table 2, Table S2) and some of them were differentially expressed when they were maintained with fruit flies fed with different fruits (Figure 4C, Table S4)

Summary

Introduction

Diachasmimoorpha longicaudata (Ashmead, D. longicaudata) is a solitary species of parasitoid wasp of several fruit fly species and has been introduced to many countries as a biological control agent.Its host, Bactrocera dorsalis Hendel, can attack many fruit species and some other plants, such as Caricaceae, Moraceae, Myrtaceae, Rosaceae, and Solaneaceae [1]. Diachasmimoorpha longicaudata (Ashmead, D. longicaudata) is a solitary species of parasitoid wasp of several fruit fly species and has been introduced to many countries as a biological control agent. Genes 2020, 11, 144 insects can detect the fly larvae by sound in rotting fruit and that the attractant could be the fungal fermentation products rather than the chemical substances produced by the fly larvae [2,3]. Carrasco and colleagues reported that the presence of fly larvae was essential for the orientation of wasps [4]. Chemical compounds produced by the larvae can be detected by wasps to locate the host [6,7]. Once the female parasitoid is on the fruit, a specific chemical compound released by some Tephritidae species can be used to enhance the host search [7]. Much is unknown about the chemosensory system of parasitoid wasps in response to their hosts

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