Comparative Study On Browning And Related Mechanisms Of Different Strains Of Tricholoma Giganteum

The life activities of edible fungis are still continuing during postharvest storage,and the increase of storage time will cause changes in their physiological and biochemical and quality,and different strains will show different storage characteristics during storage.Tricholoma giganteum is a rare edible and medicinal fungus,SCAU1 strain has unique anti-browning properties which can store 30 ds at 8~12 centigrade and doesn't change its colour.In this experiment,six strains of T.giganteum SCAU1,SCAU3,SCAU4,H49,H99 and H100 were used as experimental materials to compare the changes of browning degree and related physiological indexes of them during postharvest storage,and the genome number of the A6 mononuclear mycelium of the SCAU1 strain and the sequencing technology of high throughput two generation transcriptome were combined.The purpose of this study was to screen out the resistant storage strains of T.giganteum,and from the molecular level to explore the inherent reasons for the difference of browning degree between different strains of T.giganteum.The specific results are as follows:1.The changes of browning and browning related physiological indexes(PPO,tyrosinase,laccase and total phenol content)of six strains of T.giganteum were regularly measured,and the correlation between the indexes and browning degree was analyzed.The results showed that: The browning of six species of T.giganteum was on the rise during storage,the activity of PPO and laccase decreased,and TYR activity of H49 and SCAU3 strains increased frist and then decreased,while the other 4 strains decreased frist then increased and increased at last.The browning degree and PPO,TYR and laccase activity of the three strains of SCAU1,H49 and H100 were lower,and the browning degree and PPO activity of SCAU3 strain were the highest,but the total phenol content was not significant among the six strains(p>0.05).The correlation analysis showed that the browning degree of the six strains was significantly negatively correlated with the activity of PPO(p<0.05).In addition,only the browning degree of the SCAU3 strains had a significant negative correlation with the TYR activity(p<0.05).2.The activities of antioxidant enzymes(CAT,POD and SOD)of six strains of T.giganteum were measured regularly.The results showed that: The CAT activities of six T.giganthum strains was slow down,and the activity of POD decreased sharply in the first 6 d,followed by a slow rise and then decline,the SOD activity of the six strains in the early storage 12 d were all urgent,and then decreased at different rates.While the three antioxidant enzyme activities of the SCAU1 strains were relatively low during the whole storage period,while the SCAU3 strain was relatively high,and the difference was significant(p<0.05).3.The transcriptional data of six strains of T.giganteum were evaluated and the relationship between groups was analyzed.The results showed that: The transcriptional sequence quality of the six T.giganteum strains were good,which can be used as a follow-up bioinformatics analysis.In the correlation of gene expression level between the six strains,SCAU1,SCAU4,H99 and H100 were clustered into one group,and SCAU3 and H49 strains were respectively one of them.4.The differentially expressed genes of different strains of T.giganteum were analyzed,Four strains of SCAU1,SCAU3,H49 and H100 were selected to GO function annotation and KEGG metabolic pathways analysis.The results showed that the functional annotation of the four differentially expressed genes was mainly in metabolic process,cell component,cell process and catalytic activity.5.Differentially expressed genes and their expression patterns of the six T.giganteum strains were analyzed in the metabolic pathway of melanin formation.The results showed that the differentially expressed genes were mainly enriched in phenylalanine metabolism and tyrosine metabolic pathway in the 22 groups of different strains,and the six strains were in phenylalanine.The expression of related genes in metabolism was significantly different.The tyrosine metabolism of the six strains was mainly by oxidation decomposition pathway.In the tyrosine metabolism pathway related genes,the expression of SCAU3 strain was the highest,and the expression of SCAU1 strain was the lowest.From the above experimental results,we can see that among the six strains of T.giganteum,SCAU1 and H49 two strains showed good storage quality and market value,and the storage quality of SCAU3 strain was the least ideal.At the level of the transcriptiona,the SCAU1 and H49 strains were not easily browning may be related to the metabolic processes of the subsolid cells,the metabolic pathways of nucleoprotein,amino acids,and the gene differential expression of the melanogenesis pathway.