Metabolites In Three Mutant Strains Deficient In Three Biosynthesis Genes Of Arthrobotrys Oligospora And Their Functions

Arthrobotrys oligospora Fresen.-is a model nematode-trapping fungus that produces,a class of unique hybrid arthrosporols consisting of a polyketide-derived cyclohexene oxide with a sesquiterpene,which show an important impact on regulating fungal morphology.Previous study revealed that transferase,isomerase,dehydrogenase,hydroxylase,terpene synthetase(TPS)and polyketide synthetase(PKS)might be involved in the biosynthesis of arthrosporols.To further verify their functions and uncover the intermediates in the pathway,metabolic profiles of three mutant strains were analyzed in this study.The compounds in the mutant strains were purification with high performance liquid chromatography(HPLC)and identified with nuclear magnetic resonance(NMR)spectroscopy.The effects of the obtained compounds on the formation of 3D networks and the fungal nematode-capturing ability were also evaluated.Key results and innovations:1.The metabolite profile of amidohydrolase mutant strain ?215g281 and wild-type strain displayeda specific peak with a large cumulative amount.The target compound was isolated and purified,and was identified as 6-methylsalicylic acid,the first precursor in the biosynthesis of the arthrosporols,indicating that the substrate of amidehydrolase 215g281 is 6-methylsalicylic acid.2.There specific peaks were found in the HPLC profile of polyprenyltransferase gene mutant ?215g276,and the target compounds were isolated elucidated as toluquinol,and its two new glycosides,indicating that the polyprenyltransferase 215g276 catalyzed the substrate toluquinol.3.Three compounds STY-280-1,STY-280-2 and STY-280-3 were obtained from cytochrome oxidase(P450)gene mutant strain ?215g280,and identified as novel arthrosporoltype of compounds.The difference of the three compounds came from the length of the polyprenyl chain and degree of oxidation.4.These five new compounds were tested for their anti-nematode activity.Compounds STY-280-1,STY-280-2 and STY-280-3 displayed significant toxic activity against Caenorhabditis elegans at 6 h,which were 5.51 times,2.82 times and 3.69 times more than avermectin,respectively.5.Four mutants were evaluated for their mycelial morphology,mycelial growth,sporulation,spore germination,3D network and nematode-capturing ability.The results showed that the number of 3D network and the ability of capture nematodes of A215g280 and ?215g278 of P450 mutant strains were significantly higher than those of wild-type.At 6 h,mutant ?215g280 and ?215g278 produced many traps(382/cm2 and 314/cm2,respectively)and showed significant nematicidal activity(85.9%and 93.7%)while traps and no dead nematodes in the wild-type stain.The metabolic profiles of three mutant strains of Arthrobotrys oligospora,which may be involved in the biosynthesis of arthrosporols,displayed seven specific peaks with a large cumulative amount.The seven target compounds were isolated and purified,of which five compounds in the biosynthesis of the arthrosporols were obtained,the 6-methyl salicylic acid was identified as the first precursor in the biosynthesis;five new compounds were also obtained,of which three compounds displayed significant toxic activity against C.elegans at 6 h.The four early steps of arthrosporols biosynthesis have been verified in this study,which provide insight into the elucidation of this biosynthetic pathway for these hybrid metabolites.