Effects Of Selenium On Biological Characteristics And Substratre Bacterial Community Structure Of Ganoderma Lucidum And Auricularia Cornea

In this study,Ganoderma lucidum and Auricularia cornea were cultivated as selenium transformation carrier,and the effects of selenium enrichment on agronomic traits,active ingredients,transcriptional gene expression and substrate bacterial community were revealed,and the optimum selenium contents in the substrate of G.lucidum and A.cornea were determined.The results provide a theoretical basis for further study of selenium-enriched mushrooms and development of Se-enriched foodstuff,health products and medicines made from edible and medicinal fungi.Substrate physicochemical properties in different treatments showed:the lowest and highest substrate pH values were found at hyphal and budding stages of G.lucidum,respectively,and the substrate pH value generally increased first and then decreased with the increase of selenium content at different growth stages of G.lucidum.While,the substrate pH values were higher at hyphal and elongation stages,but was the lowest at budding stage of A.cornea.The substrate water content decreased along with the growth of G.lucidum,and was the lowest at mature stage,and it was significantly lower at mature stage than at budding stage in all the Se-treatments.However,the substrate water content of A.cornea,the substrate total nitrogen content,total phosphorus content and total potassium content of G.lucidum and A.cornea were all not significantly affected by the growth periods and selenium contents.In conclusion,both the growth period and the selenium content affected substrate physicochemical properties,and the growth period was the main factor.Agronomic traits and active ingredients of G.lucidum and A.cornea in different treatments showed:selenium promoted the mycelial growth rate of G.lucidum,and the highest was in the treatment with selenium content of 100μg/g,but the mycelial growth rate of A.cornea was significantly decreased by selenium.Selenium enrichment could increase the stipe length and the cap size,but decreased the cap thickness of G.lucidum.The yield of G.lucidum was not obviously affected by selenium,and the highest yield was gained in the treatment with selenium content of200μg/g.Moreover,the size of a single random auricular patch,the weight of a random cluster and the yield of A.cornea increased first and then decreased with the increase of selenium content in the substrate,and the biggest weight of a random cluster and the highest yield were both investigated in the treatment with selenium content of 100μg/g,significantly higher than those in control.However,selenium significantly reduced the thickness of a single random auricular patch.Selenium could greatly promote the formation of triterpene acids in G.lucidum and crude polysaccharides in A.cornea,but had no significant effect on G.lucidum polysaccharides.Furthermore,the total selenium content in the fruiting bodies of G.lucidum and A.cornea generally increased with the increase of selenium content in the substrate,suggesting their high selenium accumulation capacity.Substrate bacterial diversity analysis showed:Proteobacteria was the most abundant phylum in the G.lucidum substrate,and Firmicutes in the A.cornea substrate.The abundance of Proteobacteria decreased first and then increased with the growth of G.lucidum,and roughly decreased with the increase of selenium content in the substrate.Firmicutes showed the highest abundance at A.cornea budding stage,while,its abundance was not obviously affected by selenium.Other dominant phyla included Bacteroidetes,Acidobacteria and Actinobacteria.In addition,Lactococcus was the dominant genus in the G.lucidum substrate,and Brevibacillus in the A.cornea substrate.Furthermore,a total of 39 and 41 KEGG pathways were identified in substrate bacterial functional prediction of G.lucidum and A.cornea,respectively,and most of which were related to metabolism,environmental information process and genetic information process.PICRUSt analysis predicted that membrane transport was the most important biological pathway at different growth stages,and its abundance decreased at elongation and mature stages of G.lucidum,while was decreasing with the growth of A.cornea.What’s more,selenium enrichment had a significant impact on membrane transport pathway.A total of 16113 expressed genes were obtained from the transcriptome of G.lucidum,in which,the unigenes annotated to GO database were mainly involved in molecular functions.There obtained 2.56×10~5 genes in the A.cornea transcriptome,and the most unigenes were related to biological process.KEGG pathway annotation revealed that genes related to amino acid biosynthesis were highly expressed at budding and mature stages of G.lucidum.On the other hand,genes related to“translation”accounted for the largest proportion in the A.cornea transcriptome,and selenium enrichment exhibited an up-regulation effect on all the genes involved in“biological system”at budding and mature stages of A.cornea.Differential gene expression analysis showed that the highly expressed genes at budding stage were down-regulated at mature stage of G.lucidum and A.cornea.And the down-regulated genes at budding stage were at higher expression level at mature stage of G.lucidum.In addition,selenium-related genes in A.cornea were more active at budding stage than at mature stage.Furthermore,some potential selenium-related genes were uncovered and verified by real-time quantitative amplification in present study.Selenium-related genes in G.lucidum,such as GL23172-G,GL29881-G and GL28298-G,played a regulatory role in oxidoreductase,antioxidant activity and tryptophan synthesis.And other selenium-related genes c108476_g4 and c102698_g1in A.cornea were involved in the synthesis of various amino acids and exogenous metabolism of cytochrome P450.