Characterization of epigenetic modifications in a plant-specific glutaredoxin-mediated repression of stress-responsive gene expression

In eukaryotic cells, epigenetic modifications of DNA and histone play an important role in the regulation of gene expression. ROXY19 is a member of the plant specific CC-type glutaredoxins (GRXs). We found previously that ROXY19, by association with the TOPLESS/TOPLESS-related (TPL/TPR) family, strongly repressed a subset of genes which were positively regulated by the class II TGA factors. Arabidopsis plants ectopic expressing ROXY19 (ROXY19OE) were hypersensitive to xenobiotic chemicals due to the silencing of detoxification pathway genes. Here, we confirmed in vivo the interaction between ROXY19 and TPL. In order to understand the molecular mechanism underlying ROXY19-TPL module mediated gene repression, DNA methylation and histone deacetylation inhibitors were applied to assess the involvement of epigenetic modifications in the silencing of detoxification pathway genes in ROXY19OE plants. Promoter regions of some ROXY19 repressed genes were not methylated in wild-type/Col-0, and the methylation status were not altered in ROXY19OE. Furthermore, we investigated the role of epigenetic modifications in the antagonistic interplay between ethylene/jasmonic acid (ET/JA) and salicylic acid (SA) signaling pathways, which were supposed to be regulated by ROXY19.