A Proteomics Study On Coral Symbiont Response Under BaP Stress

Coral reef is an important part of the marine ecosystem,with extremely high biodiversity and resource productivity.Coral reefs not only provide spawning,reproduction,habitat and refuge places for marine organisms,but also provide marine products,marine drugs,and industrial materials for humans.In addition,it can also protect banks and dikes,optimize the marine environment,participate in the global carbon and nitrogen cycle,and maintain ecological balance.Coral reefs are facing increasing degradation due to changes in human activities and the natural environment.Benzo（α）pyrene（BaP）is a toxic environmental pollutant that exists widely in the environment.BaP is widely distributed,stable in nature,and has strong carcinogenicity.It can pass through surface runoff,sewage discharge,ocean dumping and the sinking of atmospheric dust are imported into the marine environment,posing a great threat to the coral reef ecosystem.Therefore,exploring the impact of BaP on coral symbiosis has great significance for the protection and management of coral reefs and the restoration of ecosystems.This study utilized the Acropora formosa,Pocillopora damicornis,and Montipora digitata from the Wanning of Hainan Province as materials to comprehensively analyze various physiological indicators of corals under stress.First,we compared the sensitivity of three corals to BaP.Secondly,the microbiological technology was used to detect the changes in the microbial colony structure of the control group and the stress 72 h group and the stress 120 h group of the Acropora formosa.In addition,The4D-DIA proteomics technology was also used to further explore the response of the Acropora formosa to BaP.We have revealed the toxicological effect mechanism of corals in response to BaP stress,providing an important scientific basis for the protection and restoration of coral reefs.This paper draws three conclusions:（1）In this experiment,the DMSO solvent control group and the BaP stress group of 1.0,12.5,25.0,50.0,100.0μg·L^-1 were set up.Samples were taken on the initial 0th day,the 3rd,5th,and 7th day of stress.The density of symbiotic zooxanthellae and the change of chlorophyll a content of coral symbionts were measured.The half effect concentration(EC₅₀)of the escape of symbiotic zooxanthellae was fitted by the"Logistic model".The results showed that when BaP stress was 3 d,5 d,and 7 d,the EC₅₀ of Montipora digitata was 750.4μg·L^-1,104.1（2）μg·L^-1,47.00μg·L^-1;the EC₅₀ of Pocillopora damicornis was 817.4μg·L^-1,97.47μg·L^-1,22.15μg·L^-1,and Acropora formosa were 59.37μg·L^-1,18.27μg·L^-1,5.38μg·L^-1.After comprehensively analyzing various physiological indicators,the results show that the Acropora formosa is more sensitive during the stress of BaP.The order of tolerance of the three corals is:Montipora digitata>Pocillopora damicornis>Acropora formosa.（3）After the Acropora formosa exposed in 50μg·L^-1 BaP for 0 h,72 h,120 h,the comparison between the control group and the treatment group showed that the coral symbionts had obvious changes in morphological characteristics.After that,metagenomics technology was used to detect the changes in the microbial colony structure of the control group and groups of under stress for 72 h and 120 h in Acropora formosa.After analyzing the microbial diversity of Acropora formosa,we found that at the phylum level,coral microorganisms are mainly Bacteroidetes,Firmicutes and Proteobacteria.In addition,Muribaculaceae and Bacteroidaceae are the main ones in the family.Although the stress has little effect on the colony structure of the dominant microorganisms,it also proves that the relative stability of the structure and function of the microbial community plays an important role in maintaining the health of Acropora formosa.（3）In order to detect the difference of the protein differential expression of the Acropora formosa between the control group and the stress for 72 h group and the stress for 120 h group,the 4D-DIA proteomics technology was used.266 differential proteins were identified in the control group and the 72 h stress group,of which 142 proteins were up-regulated and 124 proteins were down-regulated.The control group and the stress 120h group identified 272 differential proteins,of which 124 proteins were up-regulated,148 proteins were down-regulated.134 differential proteins were identified between the 72 h stress group and the 120 h stress group,of which 28 proteins were up-regulated and 106 proteins were down-regulated.In terms of molecular functions,these proteins are related to the production and metabolism of ATP,protein binding,lipid metabolism,antigen-antibody binding,in vivo enzyme activity,r RNA activity,structural molecules,etc.In terms of cell composition,some of them are related to organelles such as the Golgi apparatus and endocytosis,cell membrane functions,cell membrane structure,and cell-to-cell communication.From the perspective of biological function,it is related to detoxification process,cell self-regulation,biosynthesis,metabolism and regulation,self-regulation function,and cell autophagy function.Finally,the metabolic pathways related to carbohydrate metabolism and lipid metabolism were discovered by the KEGG metabolic pathway,which lays the foundation for further revealing the response of Acropora formosa to BaP stress.