Fig. 1

Model for uptake of dietary sRNA from the digestive tract. To carry RNAi regulatory activity on gene expression in an ingesting organism, a sRNAs from the diet (potentially packaged in (1) ribonucleoprotein (RNP) complexes or (2) in vesicles) should cross the epithelial cell (white) barrier via transcellular or paracellular mechanisms or via conveyance by immune cells (gray). They should then be taken up by proximal cells, such as stromal cells (brown) or must gain access to the circulatory (red) or lymphatic system (light gray) for systemic dissemination. b Subsequently, after exit from the circulatory system (red), uptake of sRNAs would ensue by cells of various tissues and organs (gray, brown, and yellow). None of these putative steps are understood at the level of molecular mechanism