Transcriptomic analysis of differentially expressed genes and related pathways in Harmonia axyridis after sulfoxaflor exposure

Harmonia axyridis (Pallas) is a major biological control agent that is indirectly threatened by sulfoxaflor insecticide applications targeting pests in agro-ecosystems. However, the genome-wide response of H. axyridis to sulfoxaflor remains largely unknown. Here, we used high-throughput RNA-seq technology to characterize the variation in the transcriptomic profile of second-instar H. axyridis larvae after exposure to sulfoxaflor. Two libraries were generated, with 50,702,976 and 47,005,096 clean reads for the sulfoxaflor treatment and control, respectively; these were grouped into 112,497 transcripts and 52,229 unigenes, of which 33,820 and 25,175 unigenes were respectively matched to proteins in the NCBI (Nr) and Swiss-Prot databases. From these unigenes, 794 significant differentially expressed genes (DEGs) consisting of 446 up- and 348 down-regulated genes, namely P450s, GSTs, USTs, ESTs, and others, were identified between the sulfoxaflor-treated and control groups. Furthermore, these DEGs were involved in several KEGG pathways including drug metabolism and metabolism of xenobiotic pathways. For transcriptome validation, 10 specifically expressed genes were selected and verified by quantitative real-time PCR analysis. Together, these results demonstrated that sulfoxaflor induces notable variation in the transcriptome profile and pathways of H. axyridis, which establishes a basis for further molecular investigations.