Both clathrin-mediated endocytosis and two SID transmembrane proteins are involved in double-stranded RNA uptake in the Colorado potato beetle midgut

RNA interference (RNAi), the process in which double-stranded RNA (dsRNA) is responsible for the cleavage of complementary RNA, is a powerful tool in entomology and shows promise as a crop protection strategy. However there exists considerable variability in its efficiency across different insect species for which the underlying causes are still not fully known. For cellular uptake of the dsRNA, two different mechanisms are described: Sid-1 transmembrane channel-mediated uptake and clathrin-mediated endocytosis. So far, a wide range of experiments has been conducted in insects, confirming the involvement of one of the pathways in dsRNA uptake, but never both pathways in the same species.

We investigated the role of both pathways in the uptake of dsRNA by the midgut epithelial cells in the Colorado potato beetle, Leptinotarsa decemlineata, known to have an efficient RNAi response. Through RNAi-of-RNAi experiments, we demonstrated the contribution of two different sid-1-like genes, silA and silC in the response to oral RNAi. There are also strong indications that the endocytic pathway plays an important role through the involvement of vha16  and clathrin heavy chain. We report for the first time the involvement of both pathways in dsRNA uptake in an insect species.