Gene Inspired Regulation Of Fungal Secondary Metabolism

Natural products are chemical substances produced by living organisms,which typically maintain pharmacological or biological activity,and can be used in pharmaceutical research and drug design.However,with the development of natural product chemistry,the re-discovery ratio of known compounds has been rising and thus impeded the discovery of new compounds.In the post-genomic era,a variety of biological genome information has been uncovered.In the ongoing study of fungal genomics,fungi were found to be able to synthesize far more secondary metabolites than they did under laboratory conditions,indicating the presence of orphan or cryptic biosynthetic genes.Thus,induction of cryptic genes' expression was of great significance for maintaining new natural products.In this paper,three small-molucular modifiers were used to induce new natural products from filamentous fungi Daldinia eschscholzii IFB-TL01 and Chaetomium globosum 1C51.The regulation mechanisms of these modifiers were preliminary interpreted.Specifically;In the first chapter,briefly reviewed were the progresses in the induction of cyptic secondary metabolism pathways and the exploration of new natural products.In the second chapter,we introduced that the decarboxylase inhibitor,typtamine,induced D.eschscholzii IFB-TL01 to generate a novel polyketide,spirodalesol,with unprecedented skeletal.According to previous studies,the oxidation and decarboxylation were believed to play important roles in the biosynthesis of dalesconols.Herein,we screened a series of decarboxylase inhibitors,and tryptamine was found to suppressed eventually the decarboxylation of daeschol,affording a novel polyketide spirodalesol.The mechanism of this reaction were further studied.With intermediates captured,details of this reaction were elucidated.By gene knockout and in vitro transformation,we figured out that the biosynthesis of spirodalesol was catalyzed by monooxygenase and carboxyl esterase.Spirodalesol A showed significant anti-inflammasome activity.The reconstruction of D.eschscholzii IFB-TL01 secondary metabolites caused by procaine was described in the third chapter.Procaine,a DNA methyltransferase inhibitor,changed the fungal secondary metabolism by epigenetic modulations.In this chapter,the secondary metabolites of D.eschscholzii IFB-TL01 underwent significant changes in the presence of procaine.The analysis of secondary metabolic profiles showed that the expression of laccase gene lacTL and polyketide synthase genepksTL were specifically up-regulated,which was supported by qRT-PCR analysis.To take advantage of this phenomenon,we carried out scaled-up fermentation with procaine and isolated new polyketides dalescones A-D and daeschol B,which were too scant to obtain before.The last chapter described the activation of fungal Pictet-Spenglerase gene(FPS)in C.globosum 1C51.The whole genome sequence revealed that there was a gene coding for Pictet-Spenglerase in C.globosum,but no product was detected.Tryptophan analogs were screened for the activator of FPS gene,and 1-methyl-tryptophan was found to be capable of upregulating the FPS gene,producing the corresponding Pictet-Spengler reaction products.The gene-implied enzyme inhibition strategy(GIEI)was introduced to facilitate understandings of the key diversification steps.