Comparative Transcriptome Analysis Of The Molecular Mechanisms Of Two Fungi During The Algicidal Processes

Cyanobacteria can cause algal blooms which pose significant adverse impacts on aquatic environments aquaculture,they also produce toxins which directly threaten aquatic biological safety and the health of human beings.A recent algicidal mode indicates that fungal mycelia can wrap and eliminate almost all co-cultivated algal cells within a short time span,and the color of algal media became transparent.However,the underlying molecular mechanism is still less investigated.In this study,the mycelia of Trametes versicolor F21 a and Bjerkandera adusta T1 co-cultivated with or without algal cells during the algicidal process were used as to investigate the mechanism of this new fungus-algae interaction by transcriptome analyses.Differentially expressed genes(DEGs)were further analyzed in GO term and KEGG pathway enrichment.The transcriptome of T.versicolor F21 a and B.adusta T1 during the algicidal process was compared to find the key pathway(s)and decomposition genes during the elimination of algal cells,and the results were further verified by addition of different commercial enzymes to the algal solutions.The main results are as follows:1.The T.versicolor F21 a mycelia can completely eliminated algal cells within 30 hours,while,B.adusta T1 need 48 hours.It certified that T.versicolor F21 a has the strongest algicidal ability.The mycelia of T.versicolor F21 a in 0 h,6 h,12 h and 30 h and the B.adusta T1 mycelia in 0 h,6 h,12 h,24 h,and 48 h co-cultured with algal(treatment)and pure mycelia(control)were sampled for transcriptome anaylses.Each sample had two biological repeats.2.After the cleaning of raw data,68%-73% of clean reads can be mapped to the reference genome of T.versicolor.The number of fungal DEGs were increased with the prolong incubation times.1091,1038,and 1019 fungal DEGs were detected in 6 hour,12 hour and 30 hour mycelia co-cultivated with algal cells compared with that of 0 hour.About half of the DEGs were up-regulated.69%-81% of B.adusta T1 clean reads can be mapped to B.adusta reference genome.444,555,568,647 genes were detected up-regulated and 660,817,796,929 genes were down-regulated during the co-incubation processes in the treat samples compared to that of 0 h.3.GO term enrichment analyses indicate that the DEGs of T.versicolor F21 a and B.adusta T1 were mainly related to hydrolase activity,transporter activity,oxidoreductase activity at molecular function level.At cellular component level,the DEGs were mainly associated with cell membrane,ribosome,etc.In terms of molecular function level,the DEGs of T.versicolor F21 a were primarily related to trehalose metabolic process and synthesis of several amino acids etc.The DEGs of B.adusta T1 are less than T.versicolor F21 a,including starch and sucrose metabolism,Carbon metabolism,etc.KEGG pathway enrichment analyses show that the DEGs were mainly related to Metabolism and Genetic information process.Both GO and KEGG enrichment analysis suggested that fungi probably first decompose the algal cells by several enzymes,and then transport the metabolites and energy into its own cells as raw materials for fungi growth and development via synthesis metabolism of organic acid biosynthesis and amino acid biosynthesis etc.Decomposition enzymes of fungi might play a major role in degradation algal cells.4.312 different proteins with biomass degradation capacities were predicted from the T.versicolor F21 a genome via bioinformatics analysis,249 of them could be detected by transcriptome.201 proteins of CAZymes were detected in B.adusta T1 transcriptome.28 differently expressed CAZymes families can be detected in two fungi.The results of transcriptome in two fungi showed that β-1,3-glucanase,α-glucosidase,manganese peroxidase were highly expressed,and the expression of treatment group were higher than control group.The activity of β-1,3-glucanase and the chondroitin lyase in treated samples were much higher than that in control.The activity of α-glucosidase in mycelia was slightly higher than that in control.5.Cellulase,pectinase,β-glucanase,pepsin and trypsin with different concentrations were added to algal media,and the results showed that the algal cells could be eliminated by different enzymes with different times,and pepsin showed the strongest degradation ability.The elimination of cyanobacteria is a complex process that requires a variety of enzymes to work together.Cellulase,pectinase,β-glucanase,protease may play key roles during the process.