Antifungal Activity Of Secondary Metabolites Isolated From Streptomyces Ahygroscopicus Subsp.Wuzhouensis

Streptomyces ahygroscopicus subsp.wuzhouensis is an actinomycete that produces antibiotics.The preliminary basic research found that the strain showed significant antifungal activity.In this paper,the solid fermentation product of the strain was first extracted with methanol,and then extracted with petroleum ether,ethyl acetate,and n-butanol in turn.After that,the antifungal activity of these three extracts was investigated.It was found that the ethyl acetate extract displayed strongly antifungal activity,so the ethyl acetate extract continued to be further separated and purified.In current study,nine compounds((6S,14S)-7,15-dimethyl-3H,11H-6,14-epidioxyindeno[2,1-a] indene-3,11-diimine(1),N-Dodecylaniline(2),2,6-Piperidinedione,4-[2-Hydroxy-2-(2-hydroxy-3,5-dimethylcyclohexyl)ethyl]-2,6-piperidinedione(3),4-[2’-(3’’(R),5’’(S)-3’’,5’’-dimethyl-2’’-oxocyclohexylidene)ethyl]piperidine-2,6-dione(4),2-phenylacetamide(5),(3R,5S,6R)-3,5-Diisobutyl-6-isopropylpiperazin-2-one(6),(E)-1-phenyl-2-p-methoxyphenyl ethylene(7),2-methyl-1-(3-methyl-5,6-dihydrocyclopenta[c]pyrazol-1(4H)-yl)propan-1-one(8),Nocardamine(9))including a new compound(1)and eight known compounds(3 was fist time isolated as a natural product)were isolated from Streptomyces ahygroscopicus,and the HRESIMS and NMR data of 1 and 3 were provided first time.Among these compounds,1,2,3,5 and 9 showed strongly in vitro antagonistic activity against phytopathogenic fungi and compound 3 displayed in vivo antifungal activity against M.oryzae.In addition,compound 3 could induce remarkable mycelia morphological change of M.oryzae,and the cell membrane integrity and reactive oxygen species(ROS)accumulation of M.oryzae were affected in presence of compound 3.The antagonistic mechanism of compound 3 against M.oryzae was investigated by transcriptomics analysis.Volcano plot of differential expressed genes(DEGs)revealed that 2604 DEGs were identified,with 1392 up-regulated and 1212 downregulated.Based on GO functional classification,DEGs were divided into three categories,included molecular functions,cellular components and biological processes.In category of molecular functions,the most enriched were cofactor binding,transmembrane transporter activity,transporter activity,and coenzyme binding.Integral component of membrane,intrinsic component of membrane,and membrane part were most enriched in category of cellular components.In category of biological processes,the most enriched were transmembrane transport and sulfur compound metabolic process.KEGG pathways analysis revealed that inhibition of M.oryzae by compound3 downregulated the expression of genes involved in sugar metabolism,amino acid metabolism and biosynthesis of secondary metabolites.These results provided a basis for the potential application of compound 3 in future rice blast control.