The Promoting Effect Of Intestinal Microbiota On The Growth And Development Of Red Palm Weevil(RPW),Rynchophorus Ferrugineus Olivier By Modulating Its Nutrition Metabolism

Red palm weevil(RPW),Rhynchophorus ferrugineus Olivier,is a destructive pest for palm trees worldwide.Recent evidence showed that RPW gut is colonized by microbes and altered gut microbiota can obviously modify its hemolymph nutrition content.However,the exact effects of gut microbiota on RPW phenotype and the underlying mechanisms remain elusive.Here,as compared with controls,the development duration of RPW from eggs to germ-free prepupae was markedly lengthened and their body mass was reduced as well.Furthermore,the content of hemolymph protein,glucose,and triglyceride were dropped significantly in axenic RPW larvae.Interestingly,the reintroduction of gut microbiota into the axenic treatment could significantly restore the levels of the three nutrition indices.Furthermore,it has also been demonstrated that RPW larvae mono associated with Lactococcus lactis restored the content of protein to the control ones while the feeding of Enterobacter cloacae to germ-free larvae increased the quantity of triglyceride and glucose markedly.Consequently,our evidence suggested that gut microbiota profoundly affect the development of this pest by regulating its nutrition metabolism and different gut microbes have distinct impact on host physiology.We also described IGFALS(Insulin-like growth factor binding protein acid-labile subunit)from RPW(RfIGFALS)and demonstrated how this gene is involved in regulation of nutrient metabolism during seventh instars larvae of RPW.RfIGFALS highly expressed in the gut,hemolymph,and in fat body as compared with head and epidermis.RfIGFALS was shown to be down-regulated in gut andfat body post one week dsRNA delivery,and this effect of down regulation is reflected to augmentation of glucose and TAG content in fat body.We also found that the expression level of RfIGFALS in gut was significantly downregulated by the elimination of gut microbiota.These findings suggest that gut microbiota trigger the induction of Insulin growth factor binding protein and hereby affect the nutrition metabolism in RPW.Taken together,the establishment of axenic and gnotobiotic RPW larvae will accelerate the elucidation of molecular mechanisms behind the interactions between RPW and its gut microbiota.