The Response Mechanism Of Potato Late Blight Pathogen To H₂O₂ Stress

ROS（Reactive Oxygen Species）plays an important role in triggering plant immunity against pathogens attack,which is an integral part of organism and is necessary for the growth,differentiation,and resistance to biotic/abiotic stress.ROS is indispensable for the growth,development,proliferation and pathogenicity of pathogens,but excessive ROS is harmful to the pathogen.At present,little is known about the signaling cascades in response to ROS stress in Oomycete pathogens such as Phytophthora infestans,which is the causal agent of notorious potato late blight.Here,based on biochemical,molecular biology,genetics,and multi-omics analysis（transcriptome,proteomics,and phosporylationomics）,we analyzed the influence of H₂O₂ stress on the growth,development and pathogenicity of P.infestans T30-4,and illustrated the response mechanism of P.infestans to H₂O₂ stress.In the study,we analyzed the inhibition of H₂O₂ stress on the vegetative growth of P.infestans by adding exogenous H₂O₂,and performed a comprehensive analysis of the transcriptome,proteomics,and phosphorylation omics to analyze the relationship between ROS stress response and TOR-mediated autophagy pathway.The main conclusions are:（1）H₂O₂ stress inhibited the spore germination,mycelial growth,appressorium formation and pathogenicity of T30-4 strain.These phenotypes are highly similar to those of T30-4 treated with TOR inhibitor rapamycin,which are both in a dose-dependent manner.H₂O₂ and rapamycin showed strong synergy in inhibiting growth and pathogenicity of P.infestans,indicating that there is a close relationship between ROS stress response and TOR signaling pathway.（2）Transcriptome,proteomics and phosphorylation analysis were conducted after P.infestans T30-4 was treated with IC50 of H₂O₂ for 24 h.Multi-omics analysis showed that H₂O₂ stress induced the TOR-mediated autophagy pathway.MDC staining clearly showed that in the presence of H₂O₂ and rapamycin,the autophagosome increased in a dosa-dependent manner.q RT-PCR and western blot analysis further confirmed the results of omics.（3）The transgenic potatoes containing double strand RNA of Pi TOR displayed highly resistant to P.infestans.Through constructing RNAi transgenic lines targeting Pi TOR and pathogenicity test,the transgenic lines showed resistance to P.infestans.Moreover,the si RNA levels of Pi TOR in transgenic lines were significantly up-regulated during pathogen infection.Taken together,TOR was involved in H₂O₂ response,and TOR inhibition significanly decreased the vegetative growth and pathogenicity of P.infestans.Pi TOR can be used as a potential target for genetic breeding of resistant varieties.