| Zooxanthellae is a kind of dinoflagellate that symbiotics with a variety of marine animals,and there is a stable relationship of mutualistic symbiosis between corals and zooxanthellae.As the zooxanthellae plays an important role in the growth of corals,the study of zooxanthellae is particularly important.In this study,zooxanthellae was used as the research object,and found that:(1)The growth status of Symbiodinium minutum(SM)was significantly better than that of Fugacium kawagutii(FK)under the optimal culture conditions of 25?,p H8.2,50?mol·photons·m-2·s-1.Furthermore,the chlorophyll fluorescence modulator(PAM)was used to determine the chlorophyll fluorescence value of zooxanthellae under different environmental stresses.The results showed that SM was more sensitive to abiotic environmental stresses than FK.The order of sensitivity was high temperature,high light and acidification.All results of physiological responses under stresses indicated that SM is more suitable as a model organism for further research than FK,therefore,SM was used in the subsequent experiments;(2)Based on the physiological responses of SM under the above three stress conditions,and combined with existing literatures and laboratories basis,there are still gaps in the transcriptome study of SM under the acidification condition.Therefore,the transcriptome analysis of treatment group(T)and control group(C)with acidification for 6h,12h,24h,and 120h was performed.A total of 38,790 genes were detected,of which 37,137were known genes and 1741 predicted new genes.Among the SM?6T-VS-SM?120T,there are 1371 differentially expressed genes.In terms of GO function classification,it mainly involves cellular processes,metabolic processes;cells,membranes,organelles;catalytic activity and binding functions.The enrichment results of the differential genes K EGG pathway showed that the most significant pathways involved photosynthesis,photosynthesis-antennary protein,fatty acid biosynthesis,and RNA transport,indicating that these pathways p lay a vital role in the response of SM to acidification stress.Among them,the hormone-related genes ABCG40and LOX2 have changed;they were verified by real-time fluorescent quantitative PCR using gene Actin as an internal reference.The results showed that the gene expression foldchanges of ABCG40 and LOX2 were 1.06 and 1.38 at 6h under acidification stress and0.93 and 1.18 at 12h,respectively.It shows that overall trend is consistent with the results of the transcriptome.(3)Then the proteomes of the control group(C)and the treatment group(T)samples of SM acidification stress for 24h were analyzed,it was found that the number of differential proteins between the sample groups was 142,among which 99 were up-regulated and 43 were down regulated.According to the GO functional classification,it was found that there were significant differences in functional classification and concentration of SM differential proteins under acidification stress.KEGG Pathway analysis found that differential proteins are involved in metabolic pathways,spliceosome,biosynthesis of secondary metabolite and aminoacyl-tRNA biosynthesis pathway.Among them,the proportion of down-regulated differential proteins was increased significantly in the biosynthesis of secondary metabolite.It is suggested that the secondary metabolites biosynthesis pathway plays an important role in the stress of SM acidification.Further metabolomics analysis is needed in order to obtain the hormone response mechanism of zooxanthellae under acidification stress.Therefore,the study of zooxanthellae will lay a theoretical foundation for understanding the stress response mechanism of zooxanthellae,and contribute to the research of coral bleaching mechanism,which provide targeted measures for the ecological restoration and protection of coral reef system in the future. |
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