2. NORIKA, Nordring- Kartoffelzucht- und Vermehrungs-GmbH, Parkweg 4, D-18190 Sanitz OT Groß Lüsewitz, Germany.
3. Stephan Klähn, University Freiburg, Inst. Biology III, Genetic and Experimental Bioinformatic, Schaenzlestr. 1, D-79104 Freiburg, Germany.
Plants and bacteria synthesize compatible solutes to adapt towards various environmental stress conditions. Moderate halotolerant cyanobacteria and some heterotrophic bacteria accumulate the compatible solute glucosylglycerol (GG), a compound not commonly found in higher plants. We aimed to investigate whether GG can be produced in potato and if it has an improving effect regarding stress tolerance. Potato plants were transformed with the ggpPS gene of Azotobacter vinelandii, which codes the bifunctional enzyme GG-phosphate phosphate/synthase (GgpPS) catalyzing the two-step synthesis of GG. Potato plants were generated expressing ggpPS under control of the constitutive CaMV-35S promoter or the stress-inducible rd29A promoter. The integration of T-DNA in transgenic clones was verified by PCR and transgene expression was detected on mRNA level. Transgenic potatoes with constitutive ggpPS expression accumulated GG up to 19 µmol/g fresh mass (FM) in leaves but no GG in tubers, while plants with rd29A-controlled ggpPS expression contained 10 µmol GG/g FM in leaves and up to 2.6 µmol GG/g FM in tubers. In greenhouse experiments, an increased shoot growth of the GG-accumulating potato plants was observed under salt and drought stress conditions. These results demonstrate that GG synthesis can be achieved in potato plants and might have a protective role on plant metabolism.
Keywords: Salt stress, drought stress, compatible solute, glucosylglycerol