The Function Of PdtWRKY86 In The Interaction Of Populus Deltoides × Populus Trichocarpa And Melampsora Larici-populina

Poplar is the most adaptable and widely distributed trees in the world.With the increasing acreage of poplar afforestation,China has become the world's largest poplar plantation country.There are many kinds of diseases in poplars and they are very harmful.The leaf rust disease caused by M.larici-populina is the most widely distributed and most harmful poplar leaf disease.The symptoms of two poplar varieties inoculated by M.larici-populina E4 strong strain and its phloroglucinol staining confirmed the interaction between Populus deltoides x Populus trichocarpa and E4 rust as incompatible interaction,and P.nigra × P.deltoides and E4 rust as compatible interaction.Using P.deltoides × P.trichocarpa as main research object and P.nigra× P.deltoides as control,the transcriptome data of the two cultivars at 96 h after infection with E4 rust were analyzed and found that the transcription factor was involved in the cross-reaction of poplars in response to E4 rust,NAC,WRKY,MYB,AP2 and ERF account for a large proportion.Further analysis of the five important transcription factor families in the transcriptome data revealed that most of the WRKY transcription factors up-regulate expression at 12 h and 96 h in response to E4 rust in P.deltoides × P,trichocarpa and play a positive regulatory role.The WRKY transcription factor family belongs to a family of regulatory proteins and is a critical factor in plant defense against signal transduction.Based on the transcriptome data of P.deltoides × P.trichocarpa,100 PdtWRKY genes were identified,of which 99 PdtWRKY genes corresponded to 19 chromosomes of P.trichocarpa and PdtWRKY 100 was located in Scaffold₄1.Transcriptome data analysis showed that 53 genes were differentially expressed?8 genes were down-regulated and 45 genes were up-regulated?after inoculation with E4 rust in P.deltoides × P.trichocarpa,and up-regulated genes were selected for further study.Forty-five genes were used for target gene prediction.Among them,28 genes found corresponding target genes,and there were a total of 305 target genes,establishing a regulatory network.After classifying target genes,21 target genes were found to have transcription factor activity,including PdtWRKY64,and its upstream gene was PdtWRKY86.PdtWRKY86 was up-regulated after P.deltoides × P.trichocarpa inoculation with E4 rust,and had the only target genes PdtWRKY64.PdtWRKY64 were transcriptionally regulated and 18 genes were transcriptionally regulated,12 of which were related to plant disease resistance.This shows that PdtWRKY86 has a multi-level regulatory network,its target genes are also up-regulated after P.deltoides × P.trichocarpa inoculation with E4 rust,so the PdtWRKY86 gene was selected as the research object.In order to clarify the role of PdtWRKY86 gene in the interaction between P.deltoides × P.trichocarpa and E4 rust,the gene was cloned,and the expression at seven time points was analyzed and verified by transgenics.The CDS of PdtWRKY86 is 965 bp and encodes 311 amino acids.In addition,the expression of PdtWRKY86 was up-regulated during the six other time points,indicating that PdtWRKY86 plays a positive role in the incompatible interaction between P.deltoides × P.trichocarpa and E4 rust.The PdtWRKY86 transgenic Arabidopsis plants had a slower onset and smaller lesions than the wild-type Arabidopsis-infected Botrytis cinerea and Phytophthora infestans.PdtWRKY86 transgenic Arabidopsis was more resistant than that of the wild-type Arabidopsis,indicating that PdtWRKY86 transgenic plants can improve disease resistance of transgenic plants through multi-level regulation of disease-resistance-related gene expression.In summary,it was demonstrated that PdtWRKY86 is a positive regulator of the incompatible interaction process of P.deltoides × P.trichocarpa-E4 rust.