Studies On Identification And Regulation Of Secondary Metabolites In Cordyceps Fungi.

Cordyceps spp.is a categories of fungi.And as many as 600 have been found and named,yet less than 30 of it was researched.In this field,most of research work remained in separation of compound,not much in molecular level.The fungus attract scientists' attention because of producting secondary metabolites or chemical component which have pharmacological action and cytotoxicity in process of growth.Cordyceps militaris and beauveria bassiana which have been sequenced the entire genome,were selected for reseaching.First,Crude extracts from the fruiting bodies of C.militaris were separated and purified by chromatographic technology such as macroporous resin,silica gel,Sephadex LH-20 and HPLC.The structures of isolated compounds were determined as cordycepin(1),tryptophan(2)and 5,5'-dibuthoxy-2,2'-bifuran(3)by analysis of the spectroscopic data.Compound(3),the metabolite originally identified from the plants,was isolated for the first time from C.militaris.Compound(1)and(3)showed antibacterial activity against Bacillus subtilis and Escherichia coli,while they displayed no inhibition to Saccharomyces cerevisiae.Research for filamentous fungi of B.bassiana which is asexual type of cordyceps bassiana,was also carried out.It is an extensive pathogenic bacterium and used widely in controlling insect disease as chemical pesticides.A new type of nucleoprotein transcription factor LaeA,a methyltransferase in B.Bassiana was selected for furhrer study.This study obtained B.bassiana WT,?LaeA,WT::LaeA by molecular biology experiment for the necessary research.First,we detected sporulation of strains by hemocytometer and growth phenotype.A LaeA and WT::LaeA can decrease the formation of mycelial and conidia.Meanwhile we put strains in different liquid medium for fermentation and detected the changes of the secondary metabolites via utilizing HPLC.The results showed that ?LaeA reduced the oosporein production when fermented,but raise the beauvericin production in mycelium,compared to the WT.Whereas WT::LaeA not only hindered to produce oosporein and beauvericin,but also obvious reduced UV absorbing compounds in mycelium.So we test biological activity of strains by injecting galleria mellonella,and we found that WT::LaeA cell toxicity was higher than that of the WT strains.In addition,oosporein has effect of resistance to bacterial infection by testing of antibacterial activity.Above research showed that ALaeA and WT::LaeA not only effected growth development of B.bassiana,but also hindered the expression of related gene clusters,thus have a significant impact on the secondary metabolites.All these results indicated that LaeA was a global regulatory transcription factor,and produced diversified regulation effects on other fungi.