Uptake,flow,and digestion of casein and green fluorescent protein in the digestive system of lygus besperus knight

摘要

Selected compounds were used to study physiological processes associated with digestion inthe western tarnished plant bug,lygus hesperus Knight.Durations of passage and rates of absorption,digestion,and excretion were determined for a digestible protein(casein),a non-digestible protein (green fluorescent protein,GFP),and a non-digestible carbohydrate (dextran).Dextran was used as a control to monitor the non-absorptive flow rate ingesta through the digestive system.Fluorescent tracking of FITC-conjugates of cseinand dextran,as well as immunoblotting and immunofluorescent stining of casein and GFP,were used to monitro the degradation (in vitro)and ingestion,digestion,and distributioin (in vivo)of the respective compounds.Under our experimental conditions.L.hesperus took discrete meals,feeding and excreting at 2-3h intervals.Rate of food passage was vaiable.FITC-dextran was recovered from all insects.FITC-casein ws digested extensively in in vitro homogenates of gut,hemolymph,and salivary gland.In vivo,FITC-casein ws ingested and partially absorbed as a holoprotein into the hemolymph.Ingested FITC-casein was partially degraded in the gut and hemolymph within 2 h of ingestion,and no holoprotein was foun after 12h.In contrast,there was no detectable degradation of GFP in hemolymph,gut and salivary gland homogenates after 24h of incubation.Ingested GFP was not degraded in gut or hemolygical images confirmed that GFP bound to gut epithelial cell brush-border membranes.However,the mechanism by which GFP and casein gass as holoproteins into the hemolmph remains unknown.