Analysis On Degeneration Mechanism Of Volvariella Volvacea During Mycelium Subculture Progress Based On Transcriptome

Volvariella volvacea was first cultivated in China and is the fifth most important edible fungus in the world.During the production process,it is easy to appear species degradation,which leads to the decline of yield and economic losses.The research group obtained 20strains?S1-S20?with different degrees of degradation,which were obtained by continuous subgeneration of V971?S0?for 20 months by the mycelium of the tip.In this study,transcriptome sequencing combined with physiological,biochemical and related enzymatic of mycelium analysis were used to study the degradation mechanism of V.volvacea.The main results are as follows:1.The effect of mycelia subculture on the physiological characters of V.volvacea was ascertained.The growth rate of mycelia increased obviously with passage times and decreased subsequently.Compared with S0,the growth rates and biomass of S20 mycelia decreased by47.33%and 42.67%.The LBL medium was used to stain the strain of V.volvacea,which showed that the decolorization ability of the LBL medium decreased with the degradation of the strain,and the decolorization ability was lost after S12.2.The main differential genes which were in the process of decomposition of matrix and scavenging of reactive oxygen species were obtained.Transcriptome studies showed that the number of differential genes among S4,S8,S12,S16,S20 and S0 were 1309,959,1439,1402and 1272,respectively,and the total number of differential genes were 245.The results of GO function analysis indicated that the DEGs were mainly enriched in biological adhesion,metabolic process and catalytic activity.KEGG pathway analysis revealed that DEGs were mainly in amino acid metabolism,carbohydrate metabolism,secondary metabolites synthesis,transport and catabolism.By further analysis,25 major DEGs related to Ros scavenging and45 major DEGs related to degradation matrix were obtained.RT-PCR results were basically consistent with transcriptome data.3.The effect of mycelia subculture on the content of reactive oxygen and antioxidant enzymes activity of V.volvacea was ascertained.The results showed that there was no significant difference in O₂^-·content in S0-S8,and S9-S20 increased gradually.The content of H₂O₂ increased gradually with the extension of succession time.Compared with S0,the content of S20 O₂^-·and H₂O₂ increased by 87.98%and 27.18%,respectively.The activities of SOD,CAT,GPX and GR.increased first and then decreased with the extension of the subgeneration time,and the enzyme activities of S20 decreased by 40.44%,87.60%,76.87%and 24.11%respectively compared with S0.4.The effect of mycelia subculture on the enzyme activity of decomposition matrix were clarified.The results showed that the activity of filter paper enzyme,endoglucanase,?-glucosidase,xylanase,laccase and manganese peroxidase in the substrains of V.volvacea decreased gradually.Compared with S0,the enzyme activity of S20 decreased by 60.00%,26.23%,63.69%,59.51%,68.51%and 20.66%,respectively.In summary,possible mechanisms of V.volvacea strains's degradation:continuous subculture of mycelium causes the down-regulation of gene expression related to the matrix degradated and active oxygen scavenged of the V.volvacea.Thus,these inhibited the acquisition of physical capacity of strains and the synthesis of nutrients,aggravated the toxic effect of reactive oxygen species on strains,further impedes the growth of strain and leads to the degradation of strain.The above results provide technical means and theoretical basis for identification and study of degradation mechanism of strains.