Functional Study Of The Effector Pst11857 In The Stripe Rust Fungus And Resistance Evaluation Of Two High Generation Transgenic Wheat Materials

Wheat as the second largest cereal crop in China,is widely grown throughout the country.However,wheat stripe rust caused by Puccinia striiformis f.sp.tritici（Pst）seriously threatens the safety of crops,and has caused huge economic losses in China.Stripe rust is difficult to control because of its rapid spread,wide range and frequent variation.There are also problems such as lagging disease resistance breeding.Therefore,strengthening the functional study of stripe rust effectors can help further resolve the mechanism of stripe rust pathogenesis and create durable stripe rust resistant materials using host-induced gene silencing to provide theoretical basis and disease resistance resources for green control of stripe rust.The effector Pst11857 was identified in our laboratory,and it was significantly up-regulated in the parasitic/biotrophic stage of wheat stripe rust fungus.In addition,two transgenic wheat materials,PsFUZ7-RNAi and PsCPK1-RNAi,were created in our laboratory,and they showed high disease resistance in the field.In this study,we further analyzed the virulence function of effector Pst11857 on the one hand;on the other hand,we investigated and evaluated the agronomic traits and disease resistance of the two high generation transgenic materials in the field,and the main results are as follows.1.The effector Pst11857 is an important pathogenicity factor in Pst.Subcellular localization clarified its distribution in the nucleus and cytoplasm.Transient overexpression in tobacco revealed that Pst11857 could inhibit flg22-induced reactive oxygen species burst and suppress the expression of defense-related marker genes.Transient silencing of Pst11857 in wheat using virus-induced gene silencing technology resulted in restricted mycelial growth,increased reactive oxygen species accumulation,and reduced biomass in stripe rust compared to the control.To further clarify the virulence function of Pst11857,overexpression and RNAi stable genetic material of Pst11857 were created using transgenic technology.the Pst11857-RNAi transgenic plants were significantly more resistant to stripe rust,the Pst11857 overexpression material was significantly less resistant to stripe rust,the spore production of stripe rust was significantly increased,and the accumulation of reactive oxygen species caused by stripe rust infestation was significantly reduced.In summary,Pst11857 exerts an important contribution to the virulence level of strip rust,inhibits the accumulation of host reactive oxygen species,and is an important pathogenicity factor in Pst.2.PsFUZ7-RNAi and PsCPK1-RNAi plants of T₈ still have good resistance in the field.The RNAi transgenic materials of PsFUZ7 and PsCPK1 were created using host-induced gene silencing and transgenic techniques.In this study,the T₈ generation agronomic traits of the two transgenic materials were statistically analyzed,and the results showed that there were no significant differences in plant height,spike number,spike grain number and thousand grain weight between PsFUZ7-RNAi and PsCPK1-RNAi transgenic materials and the control XN1376.In addition,the theoretical yields of different strains under natural growth and artificial inoculation were statistically analyzed,and the results showed that the wheat yield of the two transgenic strains under artificial sterilization was significantly higher than that of the control group XN1376.The pathogenesis grade analysis showed that the pathogenesis grade of XN1376 in the control group was mainly distributed in grade 5 and grade 7,and the pathogenesis grade of the two high-generation transgenic materials was mainly distributed in grade 3.In conclusion,the PsFUZ7-RNAi and PsCPK1-RNAi transgenic plants maintained comparable agronomic shape indexes compared with XN1376,with less impact on yield,and both high generation transgenic plants still showed good resistance in the field.Taken together,this study has clarified the Pst11857 is an important pathogenicity factor in Pst and further analyzed the disease resistance in two high generation field materials.In the meantime,it can provide genetic resources and theoretical support for durable control of wheat resistance to stripe rust.