Endogenous viral element-derived piRNAs are not required for production of ping-pong-dependent piRNAs from Diaphorina citri densovirus

Partial integrations of DNA and non-retroviral RNA virus genomes, termed endogenous viral elements (EVEs), are abundant in arthropod genomes and often produce PIWI-interacting RNAs (piRNAs) speculated to target cognate viruses through the ping-pong cycle, a post-transcriptional RNA silencing mechanism. Here we describe a Diaphorina citri densovirus (DcDV)-derived EVE in the genome of Diaphorina citri. We found that this EVE gives rise to DcDV-specific primary piRNAs and is unevenly distributed among D. citri populations. Unexpectedly, we found that DcDV is targeted by ping-pong-dependent viral piRNAs (vpiRNAs) in D. citri lacking the DcDV-derived EVE, while four naturally infecting RNA viruses of D. citri are not targeted by vpiRNAs. Furthermore, a recombinant Cricket paralysis virus containing a portion of the DcDV genome corresponding to the DcDV-derived EVE was not targeted by vpiRNAs during infection in D. citri harboring the EVE. These results represent the first report of ping-pong-dependent vpiRNAs outside of mosquitoes.