Study On The Mechanism Of The Actinomycete Product CP515 Inhibiting Pyricularia Oryzae

Rice blast is one of the three major diseases of rice,and its severe occurrence can cause more than60%of rice yield loss.The use of chemical fungicides is the main means to effectively control the occurrence of rice blast,but long-term use has potential health and environmental risks.At the same time,pathogenic fungi are rapidly adapting to fungicides,leading to the emergence of drug resistance.Therefore,the discovery of new natural product fungicides is of great significance to effectively control the occurrence of fungal diseases and reduce the negative impact on the environment.Streptomyces sp.SN0246 is a strain preserved in our laboratory,and the compound CP515 is one of its main secondary metabolites.Preliminary experimental studies found that CP515 has good anti-fungal activity and has potential research value.In this paper,CP515 is used as the research material,and Pyricularia oryzae is used as the target fungi.The inhibitory effect of CP515 on P.oryzae is determined,and its mechanism of action is preliminarily explored.The main findings are as follows:The inhibitory effect of CP515 against P.oryzae in vitro is determined by mycelial growth rate method and concave glass slide method.The results show that CP515 has obvious inhibitory effects on the mycelial growth and conidial germination of P.oryzae,with EC₅₀values of 14.83μg/m L and 4.45μg/m L,respectively.At the same time,through section observation and microscopic counting,it is clarified whether the compound affected the P.oryzae conidia formation.The results show that CP515 treatment could inhibit the production of P.oryzae conidia,and the sporulation inhibition rate is 52.23%.The control effect of CP515 against P.oryzae on rice plants is determined by in vivo pot experiment.The results show that CP515 has protective and therapeutic effects on the control of P.oryzae on rice plants,with a protective effect of 83.87%and a therapeutic effect of 54.84%.It has potential to be developed as a protective fungicide.Through electron microscope observation,the effect of CP515 on the morphological structure of P.oryzae mycelia and conidia is clarified.Scanning electron microscope results show that the mycelia of P.oryzae are broken and the surface shrunken;the conidia are shriveled,with uneven surfaces.Transmission electron microscope results show that the intracellular material of P.oryzae mycelia are extravasated,and the mitochondrial inner cristae disappear,the conidia are hollow and the organelles are not obvious.After CP515 treatment,the cell wall enzyme activity,cell membrane integrity,reducing sugar content,ATP content and respiration of P.oryzae mycelia are determined.The results show that the cell wall of P.oryzae is degraded,the integrity of the cell membrane is destroyed,the content of reducing sugar in the cell decreased,the content of ATP in the mycelia decreased,and the respiration rate is inhibited.Therefore,it is speculated that CP515 may inhibit the growth of mycelia by degrading the cell wall and affecting the process of glucose metabolism and energy metabolism.The effect of CP515 on gene expression of P.oryzae mycelia is determined by next-generation sequencing technology.Perform differential gene screening on sequencing results,and perform KEGG enrichment analysis on differential genes.The results show that the differentially expressed genes are highly enriched in the glycolysis/gluconeogenesis pathway,amino sugar and nucleoside sugar metabolism pathways,and starch and sucrose metabolic pathways during carbohydrate metabolism.The results of this analysis are consistent with the inference that CP515 treatment affects the glucose metabolism in P.oryzae.The above research results lay the foundation for further exploring the mode of action of CP515 and developing it into a new type of fungicide.