Pyrosequencing the midgut transcriptome of the brown planthopper, Nilaparvata lugens

The brown planthopper, Nilaparvata lugens, is a serious pest threatening rice production across the world. To identify the main features of the gene expression and the key components of the midgut of N. lugens responsible for nutrition, xenobiotic metabolism and the immune response, we used pyrosequencing to sample the transcriptome. More than 190,000 clean sequences were generated, which led to about 30,000 unique sequences. Sequence analysis indicated that genes with abundant transcripts in the midgut of N. lugens were mainly sugar hydrolyases and transporters, proteases and detoxification-related proteins. Based on the sequence information, we cloned the candidate sucrase gene; this enzyme is likely to interact with the perimicrovillar membrane through its highly hydrophobic C-terminal region. Many proteases were identified, which supported the hypothesis that N. lugens uses the proteolysis system for digestion. Scores of detoxification genes were newly identified, including cytochrome P450s, glutathione S-transferases, caroxylesterases. A wealth of new transcripts possibly participating in the immune response were described as well. The gene encoding a peptidoglycan recognition protein was cloned. Unlike in Acyrthosiphon pisum, the immunodeficiency pathway may be present in N. lugens. This is the first global analysis of midgut transcriptome from N. lugens.