title: Arabidopsis displays centromeric DNA hypomethylation and cytological alterations of heterochromatin upon attack by pseudomonas syringae.
abstract: Plant tissues display major alterations upon the perception of microbial pathogens. Changes of cytoplasmic and apoplastic components that sense and transduce plant defenses have been extensively characterized. In contrast, less information is available about modifications affecting the plant nuclear genome under these circumstances. Here, we investigated whether the Arabidopsis thaliana DNA methylation status is altered in tissues responding to the attack of Pseudomonas syringae pv. tomato DC3000. We applied amplified fragment length polymorphism analysis to monitor cytosine methylation at anonymous 5'-CCGG-3' and 5'-GATC-3' sites in naive and infected samples. Plant genomic fragments reducing methylation upon infection, including peri/centromeric repeats such as the 180-bp unit, Athila retrotansposon, and a portion of the nuclear insertion of mitochondrial DNA, were isolated and characterized. P. syringae pv. tomato-induced hypomethylation was detected by high-performance liquid chromatography assays and at the molecular level it did not seem to equally affect all 5-methyl cytosine (5-mC) residues. Nuclei from challenged tissues displayed structural chromatin alterations, including loosening of chromocenters, which also were stimulated by avirulent P. syringae pv. tomato, but not by the P. syringae pv. tomato hrpL- mutant. Finally, P. syringae pv. tomato-induced hypomethylation was found to occur in the absence of DNA replication, suggesting that it involves an active demethylation mechanism. All these responses occurred at 1 day postinfection, largely preceding massive plant cell death generated by pathogen attack.
authors.affiliation: CIQUIBIC-Departamento de Quimica Biológica, Facultad de Ciencias Quimicas, Universidad Nacional de Córdoba, 5000 Córdoba, Argentina.
authors.forename: Valeria
authors.initials: V
authors.lastname: Pavet
authors.forename: Cristián
authors.initials: C
authors.lastname: Quintero
authors.forename: Nicolás M
authors.initials: NM
authors.lastname: Cecchini
authors.forename: Alberto L
authors.initials: AL
authors.lastname: Rosa
authors.forename: María E
authors.initials: ME
authors.lastname: Alvarez
mesh_terms: D017360:Arabidopsis / Q000033:anatomy & histology / Q000235:genetics* / Q000382:microbiology*; D001483:Base Sequence; D002503:Centromere / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D019175:DNA Methylation; D004261:DNA Replication; D006570:Heterochromatin / Q000378:metabolism*; D008969:Molecular Sequence Data; D018515:Plant Leaves / Q000033:anatomy & histology / Q000378:metabolism / Q000382:microbiology; D011110:Polymorphism, Genetic; D044224:Pseudomonas syringae / Q000472:pathogenicity*; D016415:Sequence Alignment
chemical_list: D006570:Heterochromatin