Mass sequencing of cDNA libraries from salivary glands of triatomines has resulted in the identification of many novel genes of unknown function. The aim of the present work was to develop a functional RNA interference (RNAi) technique for Rhodnius prolixus, which could be widely used for functional genomics studies in triatomine bugs. To this end, we investigated whether double-stranded RNA (dsRNA) can inhibit gene expression of R. prolixus salivary nitrophorin 2 (NP2) and what impact this might have on anticoagulant and apyrase activity in the saliva. dsRNA was introduced by two injections or by ingestion. RT-PCR of the salivary glands showed that injections of 15 microg of NP2 dsRNA in fourth-instar nymphs reduced gene expression by 75+/-14% and that feeding 1 microg/microL of NP2 dsRNA into second-instar nymphs (approx. 13 microg in total) reduced gene expression by 42+/-10%. Phenotype analysis showed that saliva of normal bugs prolonged plasma coagulation by about four-fold when compared to saliva of knockdown bugs. These results and the light color of the salivary gland content from some insects are consistent with the knockdown findings. The findings suggest that RNAi will prove a highly valuable functional genomics technique in triatomine bugs. The finding that feeding dsRNA can induce knockdown is novel for insects.

Peanut seeds from different genotypes were evaluated for activities of trypsin inhibitors (serine protease), based on in vitro and in vivo assays, aiming to further selection of genitors in breeding programs for tolerance of stored grain pests. The in vitro assays were based on inhibition of insect digestive enzymes and also on thermal and pH stabilities of seed protein, while the in vivo assays were performed with insects Alphitobius diaperinus, Tribolium castaneum, Tenebrio molitor and Spodoptera frugiperda. Seed inhibitors of all genotypes inhibited bovine trypsin at 70 to 94%. The seed extract of BRS Havana inhibited T. castaneum and T. molitor up to 80% while the extract of BRS 151 L7 inhibited A. diapennus at nearly 20%. The seed inhibitors of both cultivars were stable at 80°C and also at different pH values. The two peanut genotypes are recommended as promising parents for breeding program aiming to selecting lines with tolerance to Tenebrio and Alphitobius insects.