Study On The Mechanism Of Salicylic Acid Inhibiting Phytophthora Infestans

Pathogenic oomycetes can infect various organisms such as animals,plants and humans,causing great harm to global agriculture,aquaculture and human health.Phytophthora infestans(P.infestans)is the most destructive pathogenic oomycete among them,and the potato late blight caused by Phytophthora infestans is a major threat to potato production.At present,the late blight is mainly prevented and controlled by chemical pesticides,the long-term use of chemical pesticides not only reduced its effect on pathogens,but also caused serious environmental pollution and food safety problems.Therefore,it is urgent to find effective,safe and environmental protection methods.Target of Rapamycin(TOR)is a highly conserved protein kinase in eukaryotes.TOR can respond to signals such as external nutrition,energy and stress to regulate life activities,such as cell growth,metabolism and protein synthesis.Salicylic acid is an endogenous phytohormone that can induce plant immunity to resist pathogens.However,it is not clear whether salicylic acid can directly inhibit P.infestans.In this study,P.infestans was used as the experimental materials to study the inhibitory effect of salicylic acid on P.infestans.Firstly,the inhibition effects of salicylic acid on the mycelial growth,sporulation capacity,spore germination and the virulence of P.infestans were tested.Then the antibacterial mechanism was analyzed by transcriptome and phosphoproteome.Finally,it is speculated that salicylic acid may inhibit P.infestans by targeting on the TOR signaling pathway.The research have the following results:(1)Salicylic acid could inhibit the mycelial growth,sporulation capacity,spore germination and the virulence of P.infestans,and there was dose-dependent effect.The half maximal inhibitory concentrations IC50 of salicylic acid inhibiting the mycelial growth,spore germination and the virulence of strain T30-4 were: 500 ?M,500 ?M,700 ?M and 300 ?M;At the same time,the IC50 concentrations of the above phenotype of the strain 002 inhibited by salicylic acid was: 300 ?M,300 ?M,500 ?M and 100?M.(2)The transcriptome and phosphoproteome analysis results showed that SA mainly regulated the biological functions related to RNA transport,ribosomal biosynthetic and carbon metabolism by down-regulating the expression and phosphorylation level of differentially expressed genes(DEGs),and then inhibiting the growth and development of P.infestans.(3)The TOR inhibitor AZD was used as a positive control for comparative analysis.The results of dual-group analysis showed that SA down-regulated the phosphorylation of the downstream direct substrates S6 K and RPS6 of TOR protein kinase,thus inhibiting the downstream biological functions such as translation initiation,ribosomal biosynthesis and transcription.This is highly consistent with the results of omics analysis of AZD.Therefore,it was speculated that salicylic acid could inhibit the physiological activity of P.infestans.by targeting the TOR signal pathway.In summary,this study revealed the direct toxic effect of salicylic acid on P.infestans and its target,indicating that salicylic acid has the potential to develop into an anti-oomycetes drugs.