Adaptation versus shock response to polyethylene glycol-induced low water potential in cultured potato cells |
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Authors: | Antonella Leone Antonello Costa Marina Tucci Stefania Grillo |
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Affiliation: | Research Centre for Vegetable Breeding, CNR, Parco Gussone, Via Università133. 1-80055 Portici, Italy;Dept of Agronomy and Plant Genetics, Univ. of Naples, Portici, Via Università100. 1-80055 Portici, Italy. |
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Abstract: | We compared long-term adaptation versus short-term or shock response of potato ( Solanum tuberosum ) cells to polyethylene glycol (PEG)-induced low water potential. Potato cells, which were allowed to adapt gradually to a decreasing water potential, were able to grow actively in a medium containing 20% PEG. In contrast, no appreciable gain in dry weight was observed in potato cells shocked by abrupt transfer to the same medium. PEG-adapted cells were also salt-tolerant, as they were able to proliferate in a medium supplemented with 200 m M NaCl. No visible ultrastructural changes of mitochondria or proplastids were observed in adapted cells at values of low water potential (about −2.0 MPa), which caused membrane disruption and appearance of lipid droplets in unadapted cells. ABA cellular content increased 5-fold in PEG-shocked cells but no significant increase was found in PEG-adapted cells. The intracellular content of free proline increased 12.5 times over the basal level in PEG-adapted cells and 6.5 times in PEG-shocked cells. As shown by in vivo protein labeling, shock conditions strongly inhibited protein synthesis, which was completely recovered in PEG-adapted cells. Osmotin, a protein associated with salt adaptation in tobacco, was constitutively expressed at a high level in PEG-adapted cells and accumulated in PEG-shocked cells only three days after the transfer in a medium supplemented with 20% PEG. Proline and osmotin accumulation were coincident with the increase in cellular ABA content in PEG-shocked cells, but not in PEG-adapted cells. These data suggest that this hormone is mainly involved in shock response rather than long-term adaptation. |
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Keywords: | ABA adaptation NaCl stress osmotic shock polyethylene glycol potato cells Solanum tuberosum water-stress |
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