Recent progress in RNAi research in Lepidoptera: intracellular machinery, antiviral immune response and prospects for insect pest control

• Silkworm cell lines function as models for analysis of the basic RNAi machinery.
• Involvement of miRNAs and piRNAs in antiviral defense and transposon control.
• Involvement of miRNAs and piRNAs in regulation of physiology/development.
• DsRNases and dsRNA acting as PAMP may contribute to systemic RNAi response.
• RNAi as approach for lepidopteran pest control needs optimization.

An overview of recent RNAi research in Lepidoptera is presented here, with silkworm cell lines being recently proven to represent good models for analysis of the basic RNAi machinery. In animals, involvement of the miRNA and piRNA pathway in antiviral defense and transposon control, respectively, was analyzed. Both miRNA and piRNA pathways are also shown to be involved in the regulation of several physiological and developmental processes, such as sex determination. Furthermore, recent studies have focused on the search for factors that could explain the relative refractoriness of lepidopterans to systemic RNAi, while silkworm cell lines have been engineered for efficient extracellular dsRNA uptake, with biotechnological applications. Considerable optimization needs to be done for RNAi to succeed as a method for pest control, especially regarding efficient delivery of dsRNA.