Studies On Identification Of Pathogenic Bacteria Causing Rice Panicle Blight And Precision Genome-wide DNA Methylation Characterization Of Burkholderia Glumae

Rice bacterial panicle blight disease is caused by two pathogens,Burkholderia glumae and B.gladioli.However,the B.glumae is the causal agent of this disease.The identification and comprehensive survey of the genetics and epigenetics characteristics are necessary to find sustainable control strategy.Hence,in this research study,the presence of a Burkholderia species is reported for first time,furthermore,the DNA methylation and gene expression of the B.glumae were elaborated.The Burkholderia gladioli was isolated from diseased rice plants exhibiting typical panicle blight symptoms using biochemical and molecular tests in China.DNA methylation is the most common form of epigenetic modification in prokaryotic and eukaryotic genomes and is catalyzed by DNA methyltransferase(MTase)enzymes.However,the involvement of DNA methylation in host-pathogen interaction and in pathogenicity remains largely unexplored for most of the plant pathogenic bacteria.The DNA methylation role of B.glumae genome have been not studied and detected yet.The main purpose of this project is to study the genome wide DNA methylation patterns(methylome pattern)of B.glumae strain LMG 2196 using SMRT sequencing.We identified 6mA and 4mC modification in genome of B.glumae.We used this approach to detect 11,450 putative 6mA residues and 12,049 putative 4mC residues in the pathogenic B.glumae genome.The results of DNA methylome revealed clear divergences,represented by the detection of shared and of strain-specific DNA methylation target motifs.Our findings bring key insight into bacterial methylomes and encourage further research to decipher the role of loci protected from DNA methylation in gene regulation.Interestingly,we identified the exact distribution of the 4mC and 6mA residues in whole genome.Methylome analysis by SMRT sequencing technology is the first step toward understanding the biology and functions of DNA methylation in this genus.Furthermore,most studies have assessed the transcriptome of the plant when it is exposed to pathogenic bacteria.In culture medium,most bacterial cells do not express most of the genes that are involved in pathogenicity,and it is difficult to investigate gene expression of bacterial cells in plant.Thus,we sought to simulate a patho-system similar to the real environment that would allow bacterial cells to express their pathogenic genes.For this reason,rice root exudates(as a host signal)and bacterial quorum sensing signaling molecules(as a pathogen signal)were used and their effects on bacterial gene expression were assessed using qRT-PCR and showed that enrichment medium(LB + RE + C8-AHL)was able to significantly induce all virulence genes compared with Luria Bertani(control)medium.Therefore,the data indicate that the artificial environment is very similar to the real patho-system.Bacterial cells exposed to either an artificial environment or LB medium amended with RE and C8-AHL behaved similarly to the natural environment in situ.It was observed that gene expression changes of bacterial cells are traceable in the infection process in this model system.