As shown in Figure 6 , EM analysis of representative midguts from alpha-COPI and Fluc dsRNA injected mosquitoes showed that while large characteristic RER whorls were present in the midguts of unfed Fluc dsRNA injected mosquitoes ( Figures 6A, 6B) , the RER present in unfed alpha-COPI dsRNA injected mosquitoes was disorganized and RER whorl structures were absent ( Figures 6C,  6D) . RER reorganization at 120 min post-feeding in Fluc dsRNA . Western blot analysis using a KDEL-specific antibody shows differential expression of four ER resident midgut proteins in response to amino acid feeding in Ae. aegypti mosquitoes. Total midgut protein extracts were prepared from three day old female mosquitoes that were unfed, or amino acid fed and dissected at 30 min. or 120 min. post-feeding. Proteins were resolved by 12% SDS-PAGE gel and Western blotted as described in Materials and Methods. The four unique protein bands were labeled KDEL-1 through KDEL-4 to denote their relative molecular weight, with KDEL-1 being the largest protein. Western blotting with an antibody that recognizes the ubiquitously expressed glyceraldehyde-3P dehydrogenase protein (GAPDH) was performed to control for equal protein loading. doi:10.1371/journal.pone.0018150.g003 injected mosquitoes looked similar to that of uninjected mosquitoes at the same time point, in that few if any whorls were present (compare Figures 7B and 1D ). As shown in Figure 8 , by quantitating the number and size of whorls in midgut epithelial cells from alpha-COPI and Fluc dsRNA injected mosquitoes, it is clear that loss of alpha-COPI expression in unfed mosquitoes was associated with a significant decrease in RER whorl formation. Moreover, a similar quantitative analysis of midgut epithelial cells from amino acid fed alpha-COPI dsRNA injected mosquitoes, showed highly disorganized endosomal structures and extended regions of swollen RER ( Figures 7C and 7D ). Taken together, these data indicate that functional alpha-COPI protein is required for normal whorl formation in the midgut epithelial cells of unfed mosquitoes.