Cold tolerance of potato plants transformed with yeast invertase gene

Our study was carried out with potato plants (<i>Solanum tuberosun</i> L.,cv. Désirée) transformed with the yeast invertase gene under the control of the B33 class I patatin promoter and with the proteinase inhibitor II leader peptide sequence providing for the apoplastic enzyme localization (B33-<i>inv</i> plants) and with the plants transformed with the reporter gene encoding bb-glucuronidase under the control of the 35S CaMV promoter (control plants). Exposure to 5°C during 6 days caused an increase in invertase activity and sugar content in B33-<i>inv</i> leaves in comparison with the control plants. Cell membranes of B33-<i>inv</i> plant cells showed greater cold tolerance under low temperature conditions than control plants that was recorded by electrolyte release. We supposed that higher cold tolerance of B33-<i>inv</i> plants was caused by stabilizing effect of sugar on the membranes, because B33-<i>inv</i> plants differ from the control plants in higher invertase activity, induced by expression of yeast invertase gene, and high content of sugars.