Transcriptomic Analysis On Pathogenesis Of Ziziphus Jujuba Mill. Infected By Jujube Witches' Broom Phytoplasma

Jujube(Ziziphus jujube Mill.),belonging to the genus of Ziziphus in Rhamnaceae,which is the most important economic value species in China.The occurrence of jujube disease seriously affected the yield of jujube fruit and caused serious economic loss.Therefore,it is of great significance to study the pathogenesis of jujube witches' disease.This research used healthy and infected “Muzao”(collected in Baicun,Yanchuan country)to investigate the pathogenicity and mechanism of jujube witches' broom disease.Five endogenous hormones(IAA,Zeatin,SA,ABA,and GA3)content and three antioxidant enzymes(POD,SOD,CAT)activities were determined at 10~60 days after budding.The differentially expressed genes(DGEs)were screened by transcriptome sequencing,using the leaves of 30 d after budding.Genes associated with hormones and protective enzymes metabolic pathways were identified using qRT-PCR.The main research results were as follwos.(1)In the study of changes in hormone content and protective enzyme activity,Zeatin and SA contents of infected plants began to increase significantly at 30 d and 50 d,respectively,after budding;the CAT activity tended to decrease first,and increased significantly at 60 d after budding.The significant increase of the content of Zeatin leads to the symptoms such as bud,flower and leaf,and the interaction between salicylic acid and catalase,which can stimulate the plant disease resistance.(2)In the study of transcriptome sequencing,1669 DGEs were identified unique in the diseased plants,among which 1114 DGEs were up-regulated genes and 555 were down-regulated ones.GO analysis indicated significant enrichment in biological processes,metabolic processes and catalytic activities;and KFGG pathway analysis showed significant enrichment in secondary metabolites.(3)In the quantitative analysis of key genes,among the differentially expressed genes,15 key genes were screened to be related to the metabolism of hormones and protective enzymes.The results indicated that the expression of ZjNCED,ZjGA20,ZjPAL,ZjPOD and ZjPOD5 was consistent with the change of the hormone content and the protective enzyme activity shown by qRT-PCR,which suggested that they may play important roles in the dynamic changes of endogenous hormones content and protective enzyme activity in infected plants.In summary,the genetic expression associated with hormone and protective enzyme synthesis is altered after infection,causing the source of endogenous hormones and protective enzyme activity metabolic disorders.Changes in hormone content led to plant flora,flower leaves,pedicel extension and other symptoms,protective enzyme activity to stimulate plant disease resistance and defense response.It provides theoretical support for the JWB prevention and disease-resistant variety breeding.