Analysis of the mechanism of hyperosmotic tolerance in Gracilariopsis lemaneiformis based on WGCNA

Abstract

Abstract The salt-tolerant mutants HAGL-X5, HAGL-X3, and the control were subjected to transcriptome assays after three weeks of treatment with artificial seawater of different salinities (30‰, 45‰ and 60‰). A large number of differential genes were obtained in the transcriptome, and we performed weighted co-expression network analysis (WGCNA) of these differential genes. The results showed that the samples that correlated well with salinity traits were mainly Ctr-60, X3-60 and X5-60, while the samples that correlated well with strain traits were mainly X5-30, X5-45 and X5-60. Then the modules that correlated well with salinity traits were mainly blue, red and tan modules. The modules that correlated well with strain traits were black, cyan, lightcyan, and yellows modules. KEGG enrichment of genes from the above modules revealed that the most significant enrichment pathways associated with salinity traits were the proteasome and carbon fixation by photosynthesis. The most significant enrichment pathways associated with strain traits were lipid metabolism, oxidative phosphorylation, and porphyrin and chlorophyll metabolism. From the expression analysis, the gene expression on the proteasome pathway and the carbon fixation pathway of photosynthesis was higher in all strains at a salinity of 60‰ than in all strains at other salinities. Also the gene expression of X5-60 was higher than that of Ctr-60 and X3-60 on the proteasome pathway. The expression of X5-30 genes was lower than that of Ctr-30 and X3-30 in oxidative phosphorylation as well as porphyrin and chlorophyll metabolism in strain-related enrichment pathways, where the low expression of genes of porphyrin and chlorophyll in X5-30 may be related to the higher NPQ value of X5-30. Finally, correlation analysis identified candidate genes with well correlation with salinity in proteasome and carbon fixation by photosynthesis, and with strain traits in lipid metabolism, oxidative phosphorylation, and porphyrin and chlorophyll metabolism.