Overexpression of DnaK from a halotolerant cyanobacterium Aphanothece halophytica enhances the high-temperature tolerance of tobacco during germination and early growth

DnaK 1 from a halotolerant cyanobacterium Aphanothece halophyica, was overe xpressed in the cytosol of tobacco. When the control and transgenic tobacco seeds were incubated at 27 degreesC, more than 95% of the control and tran sgenic tobacco seeds germinated. However, at a high incubation temperature, 40 degreesC, only 27% of the control seeds germinated whereas 82% of the t ransgenic seeds germinated. High temperature treatment during the imbibitio n of seeds delayed germination more in the control plants than in the trans formants although the maximum percentage of germination was similar in both plants. The quantum yields of electron transport and plant elongation were higher in the: transformant during high temperature treatment in young see dlings, but similar in older leaves. DnaK1 was detected in small amounts in seeds and its levels increased during germination. These data indicate tha t the expression of DnaK1 from a halotolerant cyanobacterium A. halophytica improved the tolerance to high temperature during germination and early gr owth. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.