Selection and Comparative Gene Expression of Midgut-Specific Targets for Drosophila suzukii

Abstract

Spotted-wing drosophila (SWD), Drosophila suzukii, is a destructive and invasive pest that attacks most small fruits and cherries. The current management for SWD involves the use of conventional insecticides. In an effort to develop a biologically based control option, the application of RNA interference (RNAi) has been investigated. To develop an RNAi approach, suitable targets must be identified, and an efficient delivery method must be developed for introducing the double-stranded RNA (dsRNA) in the midgut. In D. suzukii, we previously found that dsRNA nucleases actively degrade dsRNA molecules in the midgut. In this study, we focused on identifying biological targets focused on the midgut membrane. The profile of midgut-specific genes was analyzed and compared with the genes expressed in the whole-body using transcriptome analysis. Differential gene expression analysis revealed that 1921 contigs were upregulated and 1834 contigs were downregulated in the midgut when compared to genes from other body tissues. We chose ten midgut-specifically upregulated genes and empirically confirmed their expressions. We are particularly interested in the midgut membrane proteins, including G protein-coupled receptors (GPCRs) such as diuretic hormone 31 (DH31) receptor, neuropeptide F (NPF) recepror, toll-9, adhesion receptors, methuselah (mth), and gustatory receptor, because insect GPCRs have been offered great potential for next-generation pest management.

Keywords: Drosophila suzukii; GPCRs; differential gene expression; midgut transcriptome; spotted-wing drosophila.

Figure 1

Up- and down-regulated gene counts in Drosophila suzukii female midgut compared to its whole-body. 1921genes were up-regulated, and 1834 genes were down-regulated.

Figure 2

Gene ontology terms of Drosophila suzukii midgut-specific up-regulated genes for the three main biological categories.

Figure 3

Expression of dsRNase genes in the midgut of Drosophila suzukii as measured by RNA-Seq (A) and qRT-PCR (B). Ratios of FPKM (fragment per kilobase of transcript per million mapped reads) and FC (fold change) of the midgut (MG)/whole-body (WB).

Figure 4

Expression of membrane protein genes in the midgut of Drosophila suzukii as measured by RNA-Seq (A) and qRT-PCR (B). Ratios of FPKM (fragment per kilobase of transcript per million mapped reads) and FC (fold change) of the midgut (MG)/whole-body (WB). DH31-R: diuretic hormone 31 receptor; Adsn1&2-R: adhesion receptor1 and 2; Meth: methuselah; Gust-R: gustatory receptor; NPF-R: neuropeptide F receptor.

Figure 5

Scatter plot of the normalized gene expression levels of GPCRs between midgut and whole-body. Gene expression levels of different genes families are highlighted in different colors on the gray background scatter plot of total genes (8871) expressed in both midgut and whole-body. Two diagonal lines in the plot refer to │fold change (fc)│ = 2. Snakeskin is a midgut membrane protein, not a GPCR.