Preliminary Study On Immune Protection Mechanism Of Early Development Of Pomacea Canaliculata

Pathogenic bacteria infection and heat stress are two important threats to aquatic animals,which affect the survival and development of animals,especially larvae.Pomacea canaliculata,derived from South America,is the only freshwater mollusk of 100 malignant invasive species in the world.Its successful invasion and rapid spread benefit from its effective immune protection mechanism against the harm of pathogenic bacteria,and at the same time,the snail has the characteristics of high temperature tolerance,strong adaptability and less disease.The immune protection mechanism of its early development was analyzed.The contents of the study and the results obtained were as follows: 1 Immune related proteins of maternal transmission in Perivitelline fluid(PVF)of P.canaliculataThe protein composition of PVF of P.canaliculata was analyzed by liquid chromatography tandem mass spectrometry(LC-MS/MS)and 137 proteins were identified.By KEGG pathway analysis,it was found that 54% of the annotated protein was related to the metabolic pathway.It is confirmed that the substance in PVF mainly provides nutrition and energy for embryonic development.21 immune related proteins were detected,these proteins include lectins,hemocyanin,fibrinogen associated proteins(FREPs),scavenger receptor cysteine-rich(SRCR)and heat shock proteins(HSPs).These proteins provide protection for the smooth development of the embryo.The early development of P.canaliculata not only dependent on maternal proteins to protect the stability of the development environment of the embryo.In the early stage of embryonic development,Perivitellin ovorubin(PO: PO-1,PO-2,PO-3)and heat shock proteins(HSP40,HSP60,HSP90)related genes were detected high expression,and the expression level decreased gradually during the subsequent development.2 Effects of lipopolysaccharide and hyperthermia on the immune system of P.canaliculata juvenileThe effects of external stimuli on the immune system of P.canaliculata juvenile snail were analyzed by transcriptome techinique.402 differentially expressed genes(DEGs)were obtained after 48 h of lipopolysaccharide(LPS)stimulation,which were involved in pathogen recognition,immune stress,detoxification and oxidation.The genes associated with oxidation and detoxification are the most up regulated,including cytochrome C oxidase,cytochrome B oxidase,NADH dehydrogenase and cytochrome P450.Under heat stress,several immune related genes and signaling pathways were down regulated.Heat stress also inhibited the activity of animal DNA helicase.The result of gene enrichment indicated that oxidative dehydrogenase was stimulated by heat stress.The expression of transferase and apoptosis-related genes was up regulated.The expression of ROS and RNS related gene was not affected by heat stress.The results showed that the hemocytes of P.canaliculata juvenile still had the ability to produce ROS and RNS to kill the invading pathogens under heat stress,and the expression of HSPs(HSP70 and HSP90)was up regulated at a high level under the thermal shock.3 Immune responses in hemocytes of P.canaliculata after challenged with LPSAfter 24 hours of LPS treatment,a series of immune related genes were up regulated in hemocytes.These genes were related to the pattern recognition receptors(PRRs),cytokines,apoptosis,detoxification and hematopoiesis.Among them,cytochrome P450,Toll-like receptor 2(TLR2)and C-type lectin have the highest up regulation.LPS,as an effective pathogen associated molecular model,is often used in the study of innate immune mechanism.Through this study,we can better understand the mechanism of hemocytes in anti-infection immunity,and enrich the immunological knowledge of gastropods.4 Immune related genes expression patterns during early development of P.canaliculataIn order to cope with the complex and changeable environment,molluscs have enriched the function of their immune system genes in the course of evolution.These genes include: TLRs,Lectins,C1 q DC and FREPs.A number of genes related to superoxide synthesis and oxidation resistance have also been detected to expand to varying degrees.These genes include: gluthathione peroxidase(GPX),thioredoxin,catalase,nitric oxide synthase(NOS),glutathione synthase(GS)and cathepsin.The presence of these genes has confirmed the strong production and metabolism of ROS and RNS capabilities.It shows that the snail has an efficient response mechanism to kill and remove infected pathogens.261 P450 genes have been detected to detoxify harmful substances(pesticides ect.).The presence of P450 genes gives the snail a strong ability to survive in environments containing harmful substances.5 ConclusionsThe PVF of P.canaliculata contains a variety of maternal transferred immune related proteins,and these proteins play an important role in protecting the offspring at early stages.The snail not only depends on the proteins transmitted by its mother in PVF.It also expresses proteins related to PVF to deal with the adverse factors of the external environment.It shows that the snail has a perfect reproductive mechanism to protect the embryo from the harm of the environment.In the process of evolution,a set of immune mechanisms has been formed to cope with the changes in the external environment.In the early stage of development,several immune related genes have been identified to expand in varying degrees.It shows that the immune system of P.canaliculata has evolved to a very rich genetic resource to cope with complex and changeable external environment.A number of genes related to superoxide synthesis and oxidation resistance have been detected.The results showed that the snail had a strong ability to produce and metabolize ROS and RNS.