Long-term effects and parental RNAi in the blood feeder Rhodnius prolixus (Hemiptera; Reduviidae)

RNA interference (RNAi) has been widely employed as a useful alternative to study gene function in insects, including triatomine bugs. However, several aspects related to the RNAi mechanism and functioning are still unclear. The aim of this study is to investigate the persistence and the occurrence of systemic and parental RNAi in the triatomine bug Rhodnius prolixus. For such, the nitrophorins 1 to 4 (NP1-4), which are salivary hemeproteins, and the rhodniin, an intestinal protein, were used as targets for RNAi. The dsRNA for both molecules were injected separately into 3rd and 5th instar nymphs of R. prolixus and the knockdown (mRNA levels and phenotype) were progressively evaluated along several stages of the insect's life. We observed that the NP1-4 knockdown persisted for more than 7 months after the dsRNA injection, and at least 5 months in rhodniin knockdown, passing through various nymphal stages until the adult stage, without continuous input of dsRNA. The parental RNAi was successful from the dsRNA injection in 5th instar nymphs for both knockdown targets, when the RNAi effects (mRNA levels and phenotype) were observed at least in the 2nd instar nymphs of the F1 generation. However, the parental RNAi did not occur when the dsRNA was injected in the 3rd instars. The confirmation of the long persistence and parental transmission of RNAi in R. prolixus can improve and facilitate the utilization of this tool in insect functional genomic studies.