greater tolerance to multiple abiotic stresses as well as enhanced
expression of stress-responsive genes, suggesting that the two genes
encode negative regulators of Arabidopsis abiotic stress responses [16].
We therefore designated the genes, STRESS RESPONSE SUPPRESSOR
(STRS) 1 and STRS 2. Both genes encode members of the DEAD-box
RNA helicase family that possess RNA duplex unwinding activity, and
can promote duplex formation as well as displacement of proteins
from RNA [17]. DEAD-box RNA helicases are involved in virtually
all aspects of RNA metabolism, and are often part of supramolecular
complexes where they function in remodeling RNA and in assembly
of ribonucleoprotein structures. In a recent study, we demonstrated
that the STRS proteins are localized to the nucleolus, nucleoplasm and
chromocenters (regions of heterochromatic, transcriptionally inactive
DNA), and exhibit relocalization in response to abscisic acid (ABA)
treatment and various abiotic stresses [18,19]. We also presented strong
evidence suggesting that the STRSs are involved in RNA-directed DNA
methylation-mediated epigenetic silencing of gene expression to bring
about suppression of the Arabidopsis stress response.