Study On Changes Of DNA Methylation Of Paulownia Fortunei After Phytoplasma Infection

Paulownia,which is native to China,is an economically and ecologically important genus.The Paulownia witches’ broom caused by phytoplasma has seriously affected the cultivation and production of Paulownia,thus bringing serious economic losses to Chinese forestry.DNA cytosine methylation is one of the main epigenetic modification ways of eukaryotic genomes,and plays an important role in plant growth and development,and in response to biotic and abiotic stress.Therefore,in order to comprehensively analyze the mechanism of Paulownia witches’ broom,whole-genome methylation sequencing technology(WGBS)was performed to analyses the changes on DNA methylation levels of Paulownia fortunei before and after phytoplasma infection using healthy seedlings(PF)and phytoplasma-infected seedlings(PFI).Differentially expressed methylation regions(DMRs)were identified.The relationship between the DMRs and gene expression was analyzed to identify methylation-related genes that play important roles in the pathogenesis of Paulownia witches’ broom(Pa WB).After a series of studies,the following results were obtained:(1)After phytoplasma infection,the average methylation level of the whole genome of Paulownia fortunei was reduced.The average methylation level of cytosine changed from 14.53% to 12.47%,the average methylation level of CG decreased by about 5%,and the average methylation level of CHH decreased by about1.5%.(2)A total of 1,693 genes were obtained by combining the genes with DMRs in upstream 2k and transcriptome data.Among them,there were 748 genes with increased methylation levels,and methylation levels of 1011 genes were decreased.(3)The Pa WB-related methylation genes and their metabolic pathways were obtained,such as cytochrome P450(biosynthesis of flavonoids),chlorophyll a/b binding protein(Photosynthesis process),ARR(plant hormone signal transduction)and transcription factor WRKY33.The Expression and methylation level of these genes were both altered during the occurrence of Pa WB,indicating that changes on the photosynthesis and resistance of Paulownia were related to DNA methylation.In this study,we identified genes with DNA methylation level alteration afterphytoplasma infection,which might be of great significance for the research on Pa WB resistance and understanding of its pathogenic mechanism,and will also provide an effective reference for research on the pathogenic mechanism of other plants.