AUTHOR=Schumann Ulrike , Lee Joanne , Kazan Kemal , Ayliffe Michael , Wang Ming-Bo 

TITLE=DNA-Demethylase Regulated Genes Show Methylation-Independent Spatiotemporal Expression Patterns

JOURNAL=Frontiers in Plant Science

VOLUME=8

YEAR=2017

URL=https://www.frontiersin.org/journals/plant-science/articles/10.3389/fpls.2017.01449

DOI=10.3389/fpls.2017.01449

ISSN=1664-462X

ABSTRACT=<p>Recent research has indicated that a subset of defense-related genes is downregulated in the Arabidopsis DNA demethylase triple mutant <italic>rdd</italic> (<italic><underline>r</underline>os1 <underline>d</underline>ml2 <underline>d</underline>ml3</italic>) resulting in increased susceptibility to the fungal pathogen <italic>Fusarium oxysporum</italic>. In <italic>rdd</italic> plants these downregulated genes contain hypermethylated transposable element sequences (TE) in their promoters, suggesting that this methylation represses gene expression in the mutant and that these sequences are actively demethylated in wild-type plants to maintain gene expression. In this study, the tissue-specific and pathogen-inducible expression patterns of <italic>rdd</italic>-downregulated genes were investigated and the individual role of <italic>ROS1, DML2</italic>, and <italic>DML3</italic> demethylases in these spatiotemporal regulation patterns was determined. Large differences in defense gene expression were observed between pathogen-infected and uninfected tissues and between root and shoot tissues in both WT and <italic>rdd</italic> plants, however, only subtle changes in promoter TE methylation patterns occurred. Therefore, while TE hypermethylation caused decreased gene expression in <italic>rdd</italic> plants it did not dramatically effect spatiotemporal gene regulation, suggesting that this latter regulation is largely methylation independent. Analysis of <italic>ros1-3, dml2-1</italic>, and <italic>dml3-1</italic> single gene mutant lines showed that promoter TE hypermethylation and defense-related gene repression was predominantly, but not exclusively, due to loss of ROS1 activity. These data demonstrate that DNA demethylation of TE sequences, largely by ROS1, promotes defense-related gene expression but does not control spatiotemporal expression in Arabidopsis.</p><p><bold>Summary</bold>: <italic>Ros1</italic>-mediated DNA demethylation of promoter transposable elements is essential for activation of defense-related gene expression in response to fungal infection in <italic>Arabidopsis thaliana</italic>.</p>