High salinity and drought act on an organ-dependent manner on potato glutamine synthetase expression and accumulation

Salt and drought stresses have toxic effects on plants and diminish crop productivity. In the majority of plants these stresses provoke changes in gene expression, leading to an increased synthesis of osmoprotectors and osmorregulators. Potato plants correspond to the fourth most cultivated crop in the world. They are characterised for having low to moderate tolerance to salinity and respond by accumulating proline which functions as an osmoprotector and as an osmorregulator. Glutamine synthetase (GS; E.C.6.3.1.2) occupies a key position in nitrogen metabolism similar to that RuBisCO does in carbon metabolism and has also been implicated in the regulation of proline levels in the plant. In this work experiments were performed in order to study the effect of high salinity (250 mM NaCl) and drought on GS activity and expression patterns in several potato organs (leaves, growing tubers and roots) and on several biochemical parameters (proline, soluble protein and chlorophyll content). The data obtained suggests that regarding GS protein and transcript accumulation potato plants have a differential response to these stresses, revealing a preferential expression of different GS-encoding genes in an organ-dependent manner.