The <scp>A</scp>rabidopsis <scp>STRESS RESPONSE SUPPRESSOR DEAD</scp>‐box <scp>RNA</scp> helicases are nucleolar‐ and chromocenter‐localized proteins that undergo stress‐mediated relocalization and are involved in epigenetic gene silencing

Summary DEAD ‐box RNA helicases are involved in many aspects of RNA metabolism and in diverse biological processes in plants. Arabidopsis thaliana mutants of two DEAD ‐box RNA helicases, STRESS RESPONSE SUPPRESSOR 1 ( STRS 1) and STRS 2 were previously shown to exhibit tolerance to abiotic stresses and up‐regulated stress‐responsive gene expression. Here, we show that A rabidopsis STRS ‐overexpressing lines displayed a less tolerant phenotype and reduced expression of stress‐induced genes confirming the STRS s as attenuators of A rabidopsis stress responses. GFP – STRS fusion proteins exhibited localization to the nucleolus, nucleoplasm and chromocenters and exhibited relocalization in response to abscisic acid ( ABA ) treatment and various stresses. This relocalization was reversed when stress treatments were removed. The STRS proteins displayed mis‐localization in specific gene‐silencing mutants and exhibited RNA ‐dependent ATP ase and RNA ‐unwinding activities. In particular, STRS 2 showed mis‐localization in three out of four mutants of the RNA ‐directed DNA methylation ( R d DM ) pathway while STRS 1 was mis‐localized in the hd2c mutant that is defective in histone deacetylase activity. Furthermore, heterochromatic R d DM target loci displayed reduced DNA methylation and increased expression in the strs mutants. Taken together, our findings suggest that the STRS proteins are involved in epigenetic silencing of gene expression to bring about suppression of the A rabidopsis stress response.