Over-expression of PR-10a leads to increased salt and osmotic tolerance in potato cell cultures

The PR-10a protein (formerly STH-2) is known to be induced by biotic stress in potato. The present study demonstrates that transgenic suspension cells of the potato cultivar Desiree over-expressing the PR-10a protein exhibit significantly increased salt and osmotic tolerance compared to the respective wild type cells. A comparison of the proteome pattern of Solanum tuberosum suspension cultures cv. Desiree before and after the treatment with NaCl or sorbitol under equiosmolar conditions (740 mOs/kg) revealed the pathogenesis related protein PR-10a to be one of the predominant differentially expressed proteins in potato cell cultures. The pr-10a mRNA was confirmed to be present by RT-PCR from salt challenged suspension cells and was transcribed into cDNA. For PR-10a over-expression Agrobacterium tumefaciens mediated transformation of the potato cells and a dicistronic vector harboring the cDNA of the pr-10a gene linked to a luciferase gene by an IRES (Internal Ribosome Binding Site) was used. The IRES mediated translation leads to co-expression of PR-10a and luciferase in a fixed ratio. By non-invasive luciferase assay homologous PR-10a over-expressing callus was identified after selection on phosphinothricin supplemented medium. This callus was used for the setup of a transgenic suspension culture. Along with increased salt and osmotic tolerance the transformed culture showed changed proline and glutathione levels under abiotic stress conditions in comparison to the wild type.