Abiotic tolerance of tobacco plants transformed with DnaK from a halotolerant cyanobacterium Aphanothece halophytica

Abstract

A. halophytica can grow at high external salinity up to 3 M NaCl. The DnaK1 from A. halophytica was shown to exhibit extremely high protein folding activity at high salinity conditions. To test the role of the heat shock protein DnaK/Hsp70 in salt tolerance, tobacco plants were transformed with DnaK1 from a halotolerant cyanobacterium A halophytica which was overexpressed in the cytosol. The growth rate and photosynthetic activities of the transgenic and control tobacco plants were similar under non-stressed conditions. After 3 days of treatment with 0.6 M NaCl, the CO2 fixation rate decreased to 40% of that in the non-stressed plants whereas its activity in the transgenic plants was about 85% of that in the non-stressed plants. When the control and transgenic tobacco seeds were incubated at 27°C, more than 95% seeds germinated in both the control and transgenic tobacco. However, at a high incubation temperature, 40°C, only the 27% control seeds germinated whereas the 82% transgenic seeds germinated. These data indicate that the expression of A halophytica DnaK in tobacco confers the tolerance of tobacco for salt- and high temperature-stresses.