The Arabidopsis STRESS RESPONSE SUPPRESSOR DEAD‐box RNA helicases are nucleolar‐ and chromocenter‐localized proteins that undergo stress‐mediated relocalization and are involved in epigenetic gene silencing

Abstract

SUMMARYDEAD-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 SUPPRESSOR1 (STRS1) and STRS2 were previously shown to exhibit tolerance to abiotic stresses and upregulated stress-responsive gene expression. Here, we show that Arabidopsis STRS-overexpressing lines displayed a less tolerant phenotype and reduced expression of stress-induced genes confirming the STRSs as attenuators of Arabidopsis 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 ATPase and RNA-unwinding activities. In particular, STRS2 showed mis-localization in three out of four mutants of the RNA-directed DNA methylation (RdDM) pathway while STRS1 was mis-localized in the hd2c mutant that is defective in histone deacetylase activity. Furthermore, heterochromatic RdDM 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 Arabidopsis stress response.

The DEAD-box RNA helicases and multiple abiotic stresses in plants: a systematic review of recent advances and challenges

“…Most of the RNA helicases may have sequence similarity or may have similar helicase core but they are functionally distinct . Besides conformational changes of RNA duplex, RNA helicases are also involved in abiotic stress responses in plants (Owttrim, 2006;Koroleva et al, 2009a;Khan et al, 2014;Liu et al, 2016). Recently, the DEAD-box RNA helicases have been extensively studied in model and crop plants to explore their functional utilities to develop multiple abiotic and biotic stress resistance.…”

“…Recent studies have shown that AtRH7 DEAD-box gene confers cold tolerance in Arabidopsis thaliana . Some of the DEAD-box genes mediate epigenetic gene silencing of the stress induced genes expression through RNA directed DNA methylation (RdDM) (Kant et al, 2007;Barak et al, 2014;Khan et al, 2014). Using model oilseed crop Brassica napus, our group has studied the differential expression analysis of genes involved in abiotic stresses (Havlickova et al, 2013;Keshavaiah et al, 2014).…”

“…Confers cold stress tolerance by interacting with CbGRP (cold responsive glycine rich RNA binding protein) Arabidopsis thaliana Negative (Kant et al, 2007;Khan et al, 2014) strs2 Arabidopsis thaliana Negative (Kant et al, 2007;Barak et al, 2014; …”

DEAD-box RNA helicases and epigenetic control of abiotic stress-responsive gene expression

“…6 Mutations in either gene caused increased tolerance to salt, osmotic and heat stresses, as well as enhancement of stress-induced gene expression, whereas overexpression yielded the opposite effect. 7 We therefore designated the genes, STRESS RESPONSE SUPPRESSOR1 (STRS1) and STRS2. We further demonstrated that STRS1 and STRS2 are part of the ABA-independent and ABA-dependent stress regulatory networks, and function to attenuate the stress-induced expression of transcriptional activator genes.…”

Analysis of the role of RNS2 and autophagy in the turnover of ribosomal RNA in Arabidopsis thaliana

“…AtHELPS seems to functions as a negative regulator during low potassium stress ). Other DEAD-box helicases have been implicated in a variety of physiological processes in plants including determination of cell fate, biotic and abiotic stress, gene silencing, and growth (Kobayashi et al 2007;Guan et al 2013;Gu et al 2014;Khan et al 2014;Tuteja et al 2014;Zhang et al 2014).…”