DHH1/DDX6-like RNA helicases maintain ephemeral half-lives of stress-response mRNAs

Defence genes must be switched off when pathogen pressure is weak to favour growth and development programmes. Three RNA helicases participate in this repression by controlling how stress-specific mRNAs are stabilized and translated. Gene transcription is counterbalanced by messenger RNA decay processes that regulate transcript quality and quantity. We show here that the evolutionarily conserved DHH1/DDX6-like RNA hellicases of Arabidopsis thaliana control the ephemerality of a subset of cellular mRNAs. These RNA helicases co-localize with key markers of processing bodies and stress granules and contribute to their subcellular dynamics. They function to limit the precocious accumulation and ribosome association of stress-responsive mRNAs involved in auto-immunity and growth inhibition under non-stress conditions. Given the conservation of this RNA helicase subfamily, they may control basal levels of conditionally regulated mRNAs in diverse eukaryotes, accelerating responses without penalty.