Roles Of Actin Cytoskeleton In Nonhost Wheat Against Tomato Powdery Mildew And Expression Of Related Genes

Tomato powdery mildew harm seriously in the greenhouse facility of north protected land and open area in recent years,showing a spreading trend.Currently,resistant varieties of tomato powdery mildew are still quite shortage,the selection of resistant varieties is an ideal way of controlling tomato powdery mildew,and the study of the resistance mechanism of tomato powdery mildew is the basis and premise for resistance breeding.Non-host resistance is the most common resistance mechanism of plant to identify and defend potential pathogens,and the cytoskeleton acts an important role in the non-host resistance of plant.Histochemical methods were used to investigate the infection process and main resistance responses after inoculation of Oidium neolycopersici into non-host wheat,the roles of actin depolymerization in the main resistance responses of non-host wheat against O.Neolycopersici.Meanwhile,qRT-PCR was applied to analyze the expressions of the candidate gene related to microfilaments ADF4 and pathogenesis-related protein genes PR1,PR2 and PR3,the results can provide a further understanding of the non-host resistance mechanisms.The main results are as follows:1.The infection process of O.neolycopersici on non-host wheat: histochemical staining results showed that the germination rate of O.neolycopersici on non-host wheat were uninhibited,which were 77.5% at 12 h,and reaching above 85% at 24 h,spores produce the germ tubes,forming cracked disc shape appressorium,and the number of cracked disc were1~5,then papillae was found under the appressorium,the deposition rate of papillae growing overtime,peaking at 39.99% at 96 h.2.The main resistance responses in the non-host interaction of wheat against O.neolycopersici: the results of DAB and typan blue staining showed significant accumulation of reactive oxygen(H2O2)and production of hypersensitive response(HR)in the non-host interaction.H2O2 accumulation occured amount in the early period of non-host interaction,peaking at 24 h,while the number of hypersensitive gradually increased,and the necrosis rate reached 86.35% at 96 h,indicating that H2O2 accumulation and HR production remains the primary resistance mechanism of non-host wheat against O.neolycopersici.3.The effects of actin depolymerization on the main resistance responses in the non-host interaction between wheat and O.neolycopersici: Before inoculation,wheat leaveswere treated with actin cytoskeleton depolymerization agent CE,the results showed that the accumulation of H2O2 and production of HR were reduced and delayed.After the CE treatment,the amount of H2O2 accumulated and HR generated were less than the control treatment,which showed that the actin cytoskeleton polymerization plays an important role in wheat resistance against the infection of non-pathogenic.4.qRT-PCR was applied to analyze the expressions of the candidate gene related to microfilaments ADF4 and pathogenesis-related protein genes PR1,PR2 and PR3 in non-host interaction.The lower expression of ADF4 was detected at each time-point except 36 h.ADF can promotes actin depolymerization,and the lower expression of actin depolymerization factor indicates that the completion of actin cytoskeleton is necessary to the non-host resistance of plant.Meanwhile,the pathogenesis-related protein genes PR1,PR2 and PR3 were upregulated at the early infection period after inoculation,and reaching expression peak mainly at 12 h.The results indicated that PR genes are involved in the early period of non-host wheat against O.neolycopersici.