P38 Signaling Pathway Participate In The Regulation Of Avoidance Behavior To PA14 In Caenorhabditis Elegans

The soil nematode Caenorhabditis elegans, which is a kind of simple multicellular organisms, feeds on the organic bacteria in the environment. Meanwhile, the bacteria food can also affect a variety of behaviors of nematodes, such as feeding, locomotion, thermotaxis and aerotaxis. In addition, there are a lot of pathogenic bacteria in the soil, some of which can even kill C. elegans and induce an aversive learning response. The p38 innate immune pathway, which is one of the most traditonal innate immune pathways, has multiple tissue-specie activities in the regulation of immune and behavioral responses to pathogenic bacteria. In the process of regulate innate immune, TIR-1, an ortholog of the mammalian TIR domain adaptor protein SARM, acts upstream of the NSY-1-SEK-1-PMK-1MAPK. However, in regulation to the avoidance behavior, the relationship between TIR-1 and NSY-1-SEK-1-PMK-1MAPK are unknown. Based on this research background, we directly detected the avoidance index of the mutant strains in P38 pathway, and find out their different roles in immunity. Furthermore, our study also suggested the molecular signaling pathway functioning downstream to PMK-1 MAPK.The main results were as follows:1.The different genes in P38 pathway have negative or positive regulation to the avoidance behavior of PAH. It is observed that there is a higher avoidance index in nsy-1(agS), sek-1(km4) and pmk-1 (km25) strains, but the lower avoidance index in tir-1(gk264) mutant. Therefore, the results here suggested that NSY-1, PMK-1 and SEK-1 restrain the avoidance behavior, but the opposite is TIR-1. After we have successfully constructed the double mutants of pmk-1 (km25);tir-1(gk264) and pmk-1 (km25);sek-1(km4) and then determined their avoidance, the results suggested SEK-1, PMK-1 functioned in the same pathway; however, TIR-1 and PMK-1 are localized in parallel pathway to regulate the avoidance behavior to PA14 in C.elegance. On the other hands, the learning ability had been found unchangable in nsy-1(ag3), sek-1(km4) and pmk-1 (km25) strains. Finally, atf-1 and skn-1, which are direct downstream to pmk-1, do not participate in the regulation of avoidance behavior.2. The PMK-1 expressed in ADF neurons regulate avoidance behavior to PA14 in C.elegans. The gene of pmk-1 is both expressed in the intestine and neurons. Actually, intestine expressive pmk-1 participated in regulation of innate immune. However, the function of PMK-1, which is expressed in neurons, is still unknown. Double immunofluorescent staining revealed co-localization of TPH-1 and PMK-1 in ADF neurons. In addition, the expression of PMK-1 in neurons could rescue the phenotype of pmk-1 mutant strain, suggesting that PMK-1 expressed in neurons plays a main role in the regulation of avoidance behavior to PA 14. Furthermore, the perception of PA 14 smell and physical pathogenic damage were shown to be required in regulation of avoidance behavior by PMK-1.3. The serotonin synthesis in ADF neurons and neuropeptide NPR-1 expression in RMG neurons act downstream of P38 pathway to regulate avoidance behavior in C.elegans. We have screened most of the genes that had been reported to involve the regulation of avoidance behavior in different pathways, and found out that tph-1 and npr-1 should be act downstream of PMK-1 MAPK via RT-PCR and RNAi testing. Furthermore, our date confirmed that in ADF neurons, the reduced expression of PMK-1 activated serotonin synthesis. Meanwhile, in RMG neurons, the expressional level of NPR-1 enhanced after pmk-1 was mutant. In addition, TPH-1 and NPR-1 were parallel in the regulation of avoidance behavior.4. Wnt signaling pathway and actin-related gene msi-1 act downstream to neuropeptide NPR-1 to regulate avoidance to PA14 in C.elegam. When the transcriptomics of N2 and npr-1(ad609) strains after PA 14 tanning was performed, the genes that had different expressional levels were determined. Then we selected some genes related to wnt signaling pathway, endoplasmic reticulum stress and actin. and assayed the avoidance via RNAi. We demonstrate that the genes mig-1, dsh-1, cfz-2 related to Wnt pathway and the actin-related gene msi-1 might participate in the regulation of avoidance downstream to neuropeptide NPR-1 in C.elegans.The innovations of our investigation are concluded as follows:1. It is firstly revealed that the genes of P38 are not in the same molecular pathways to regulate avoidance behavior to PA 14 in C.elegans.2. It is firstly confirmed that PMK-1 is both expressed in the intestine and neurons. Furthermore, intestine expressive PMK-1 participate in the regulation of innate immune, and the neurons expressive PMK-1 regulate the avoidance behavior to PA 14 in C.elegans.3. It is firstly reported that TPH-1 expressed in ADF neurons and NPR-1 expressed in RMG neurons act parallel downstream to PMK-1 regulate avoidance behavior to PA 14. Moreover, Wnt pathway related genes mig-1, dsh-1, cfz-2 and the actin related gene msi-1 are downstream target genes of NPR-1 in the regulation of avoidance behavior to PA 14 in C. elegans.