Surviveal or growth: plant acclimation versus shock response to osmo-stress

The plant response to osmotic stresses, intensively investigated thus far, appears to be driven by complex multicomponent signalling pathways, as revealed by studying plant molecular response to short and intense stress conditions, which are, however, irremediably associated with growth impairment and a consequent yield loss. From an ecological and breeding perspective, more informative are efforts aimed to uncovering the mechanisms underlying the plant response to mild and prolonged exposure to osmotic stress. To address this point, potato cells (Solanum tuberosum) were acclimated gradually to osmo-stress, and we demonstrated, by a transcriptomic analysis, that distinct regulatory gene networks from those induced upon acute stress were activated. In particular, we provided evidences that acclimation requires a major effort in terms of transcriptional regulation and that distinct transcription factors promote the differential response to short- or long-term water limiting conditions. Modulation of ethylene signalling network appear to be a distinctive trait of gradual acclimation to osmo-stress and may be part of a vast environmentally-driven epigenetic program, which needs further investigations. Gene expression patterns and functional analyses in potato plants confirmed that valuable information on primary acclimation response are achieved from using cell cultures (1, 2). Finally, we provide evidence that AtRGGA gene, coding for a glycine-rich RNA-binding protein, ortholog of StRGGA selected from the catalogue of genes specifically induced in cells acclimated to water limiting conditions, confers tolerance to osmotic stress when overexpressed in the model species Arabidopsis thaliana (3).