Comparative Analysis of Short- and Long-Term Changes in Gene Expression Caused by Low Water Potential in Potato (Solanum tuberosum) Cell-Suspension Cultures

Abstract

To dissect the cellular response to water stress and compare changes induced as a generalized response with those involved in tolerance/acclimation mechanisms, we analyzed changes in two-dimensional electrophoretic patterns of in vivo [35S]methionine-labeled polypeptides of cultured potato (Solanum tuberosum) cells after gradual and long exposure to polyethylene glycol (PEG)- mediated low water potential versus those induced in cells abruptly exposed to the same stress intensity. Protein synthesis was not inhibited by gradual stress imposition, and the expression of 17 proteins was induced in adapted cells. Some polypeptides were inducible under mild stress conditions (5% PEG) and accumulated further when cells were exposed to a higher stress intensity (10 and 20% PEG). The synthesis of another set of polypeptides was up-regulated only when more severe water-stress conditions were applied, suggesting that plant cells were able to monitor different levels of stress intensity and modulate gene expression accordingly. In contrast, in potato cells abruptly exposed to 20% PEG, protein synthesis was strongly inhibited. Nevertheless, a large set of polypeptides was identified whose expression was increased. Most of these polypeptides were not induced in adapted cells, but many of them were common to those observed in abscisic acid (ABA)-treated cells. These data, along with the finding that cellular ABA content increased in PEG-shocked cells but not in PEG-adapted cells, suggested that this hormone is mainly involved in the rapid response to stress rather than long-term adaptation. A further group of proteins included those induced after long exposure to both water stress and shock. Western blot analysis revealed that osmotin was one protein belonging to this common group. This class may represent induced proteins that accumulate specifically in response to low water potential and that are putatively involved in the maintenance of cellular homeostasis under prolonged stress.

Proteomics for genetic and physiological studies in plants

“…Protein response depends on the type of stress: Leone et al [98] showed that the protein response fo Solanum tuberosum cell suspensions abruptly submitted to low water potential was different from the response to gradual decrease of the water potential. ABA also induced most of proteins induced by abrupt treatment.…”

The Arabidopsis RNA-Binding Protein AtRGGA Regulates Tolerance to Salt and Drought Stress

“…Potato (Solanum tuberosum 'Desirèe') cell cultures were generated, maintained, and gradually or abruptly exposed to 20% (w/v) PEG 8000 as described previously (Leone et al, 1994;Ambrosone et al, 2011). Arabidopsis (Arabidopsis thaliana) MM2D cells (ecotype Landsberg erecta) were maintained as described (Menges and Murray, 2002) in continuous dark conditions.…”

Differential gene regulation in potato cells and plants upon abrupt or gradual exposure to water stress

“…Our data indicated that water stress imposed gradually is compatible with active cellular growth (Leone et al 1994a), primarily due to restored normal protein synthesis (Leone et al 1994b), proline and polyamine accumulation (Scaramagli et al 2000) and changes in membrane composition and fluidity (Leone et al 1996). Although a cell system is not representative of the whole plant's response, the data indicate that external conditions used to impose water stress are critical to infer whether the observed transcriptional changes are associated to cellular damage rather than to the plant's ability to sustain acceptable growth at otherwise non permissive water status.…”