Identification of Himetobi P virus in the small brown planthopper by deep sequencing and assembly of virus-derived small interfering RNAs

Profiling and assembly of virus-derived small interfering RNAs (siRNAs) using next-generation sequencing technologies have been very useful for identification and diagnosis of a number of plant and invertebrate viruses. In this work, we have conducted high-throughput pyrosequencing and bioinformatic analysis of the small brown planthopper (SBPH, Laodelphax striatellus), and these analyses unexpectedly showed that the Himetobi P virus (HiPV) was present in our laboratory cultures. HiPV was also found to infect our brown planthopper (BPH, Nilaparvata lugens) and the white-backed planthopper (WBPH, Sogatella furcifera) cultures. The majority of the HiPV-derived siRNAs (Hd-siRNAs) were 21 and 22 nucleotides in length and nearly two-thirds of the siRNAs originated from the HiPV genomic RNA strand. The Hd-siRNAs were evenly distributed across the genome and this indicates that the HiPV genome contributes uniformly to production of Hd-siRNAs. Although HiPV infection appeared to be innocuous to the SBPH, alterations of gene expressions involved in reproduction, cytoskeleton structure and defense responses such as RNA interference pathways (RNAi) genes were observed. Furthermore, we demonstrated that silencing Agronaute 2 in L. striatellus enhanced HiPV accumulation, and this observation provides evidence for the existence of RNAi defenses against HiPV in the SBPH.