Molecular physiology of insect midgut

New approaches have led to advances in the molecular knowledge of digestion and nutrient absorption in insects. Cell fractionation with proteomics revealed the molecular composition of the insect midgut microvill and associated with RNA interference supported a model of microapocrine secretion. The use of mainly transcriptomics confirmed the widespread occurrence of a midgut mucus layer and clarified the differences between peritrophic membrane peritrophins and cuticular proteins analogous to peritrophins. The use of recombinant enzymes and bioinformatic tools resulted in a better understanding of lysosomal enzymes as digestive enzymes in curculionidae beetles and hemipterans, the characterization of several plant cell wall-degrading enzymes and the finding of their origin by horizontal gene transference from bacteria. Proteomics, transcriptomics and in vivo experiments with inhibitors clarified aspects of midgut buffering, nutrient absorption and midgut fluid fluxes. In the last case, the results support a model of digestive enzyme recycling to avoid enzyme excretion.