When the expression of immune response and 5 NUC genes Tofacitinib Citrate was silenced, higher fly mortality and reduced oviposition were obtained when com pared to controls. Interestingly, knockdown of FER light chain and vATPase genes resulted in lower fly mortality, and 6 and 16 fold decrease in oviposition when com pared to control dsRNA injected flies. Discussion The effective control of horn fly infestations requires the design of new control strategies. Genomics and func tional genomics studies are important to understand basic biological questions and to identify new targets for improved control strategies. Recently, gene expression analysis was reported in horn fly embryos, larvae and adult females. However, this is the first report of functional genomics studies in this species.

ESTs sequenced and assembled in this study provided new sequence information for horn fly. The assembled unigenes without sequence similarity to sequences in public databases probably represented unique transcripts for horn fly or corresponded to proteins that have not yet been identified in related organisms due to incom plete genomic information. However, it cannot be excluded that the identified ESTs represent parts of known proteins whose similarities are located in parts of the sequence that are not covered by the analyzed ESTs. The number of ESTs assembled into a certain unigene roughly reflected the relative abundance of corresponding mRNAs since the cDNA library from female horn flies used in this study was not normalized.

We found that 100 unigenes, containing 25% of the ESTs, corresponded to serine proteases, indicating that this group represented the most abundantly expressed genes in abdominal tis sues of partially fed female horn flies. In fact, the uni genes with the largest number of ESTs represented members of the serine protease family, thus suggesting that posttranslational modification and protein turnover were highly active in partially fed female flies. The high proportion of ESTs present as singleton sequences when compared to contigs reflected a low diversity in our dataset, probably due to the presence of paralogs and sequence polymorphisms for some unigenes. In fact, sequence analysis of serine protease unigenes makes at this point difficult to discriminate between paralogs and ESTs representing sequence poly morphisms within the horn fly population.

RNAi was used to functionally characterize selected horn fly genes in adult female flies. To our knowledge, this is the first report of RNAi in horn flies. RNAi has been used to study gene function in insects and other arthropods and to screen for candidate protec tive antigens in ticks. Although with some fly mortality Batimastat probably due to dsRNA injection with a Hamil ton syringe, the RNAi method used here produced repro ducible results in female horn flies.