Abstract
BackgroundThe brown planthopper (BPH), Nilaparvata lugens (Stål), one of the most serious rice insect pests in Asia, can quickly overcome rice resistance by evolving new virulent populations. The insect fat body plays essential roles in the life cycles of insects and in plant-insect interactions. However, whether differences in fat body transcriptomes exist between insect populations with different virulence levels and whether the transcriptomic differences are related to insect virulence remain largely unknown.Methodology/Principal FindingsIn this study, we performed transcriptome-wide analyses on the fat bodies of two BPH populations with different virulence levels in rice. The populations were derived from rice variety TN1 (TN1 population) and Mudgo (M population). In total, 33,776 and 32,332 unigenes from the fat bodies of TN1 and M populations, respectively, were generated using Illumina technology. Gene ontology annotations and Kyoto Encyclopedia of Genes and Genomes (KEGG) orthology classifications indicated that genes related to metabolism and immunity were significantly active in the fat bodies. In addition, a total of 339 unigenes showed homology to genes of yeast-like symbionts (YLSs) from 12 genera and endosymbiotic bacteria Wolbachia. A comparative analysis of the two transcriptomes generated 7,860 differentially expressed genes. GO annotations and enrichment analysis of KEGG pathways indicated these differentially expressed transcripts might be involved in metabolism and immunity. Finally, 105 differentially expressed genes from YLSs and Wolbachia were identified, genes which might be associated with the formation of different virulent populations.Conclusions/SignificanceThis study was the first to compare the fat-body transcriptomes of two BPH populations having different virulence traits and to find genes that may be related to this difference. Our findings provide a molecular resource for future investigations of fat bodies and will be useful in examining the interactions between the fat body and virulence variation in the BPH.
Highlights
The insect fat body, which consists mainly of adipocytes, is a central storage depot for excess nutrients
We present here the first comprehensive evaluation of the fat body transcriptome of the brown planthopper (BPH) using high-throughput sequencing and a comparative expression analysis between two BPH populations with different virulence levels
Gene Ontology (GO) analysis of all annotated unigenes showed a similar distribution of gene functions between them
Summary
The insect fat body, which consists mainly of adipocytes, is a central storage depot for excess nutrients. The fat bodies in certain insect species, such as cockroaches, beetles, and some Hemiptera (e.g. planthoppers, aphids), contain mycetocytes [7] These mycetocytes have symbiotic microorganisms which are supposed to produce essential components that insects cannot produce alone and which may play a role in the formation of biotypes or virulent populations of host insects, such as whiteflies, aphids and the brown planthopper (BPH), Nilaparvata lugens (Stal) [7,8,9,10,11]. Whether differences in fat body transcriptomes exist between insect populations with different virulence levels and whether these differences are related to insect virulence remain unanswered questions. Whether differences in fat body transcriptomes exist between insect populations with different virulence levels and whether the transcriptomic differences are related to insect virulence remain largely unknown
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