Salt Tolerance-Related Protein: a new protein involved in plant adaptation to low temperatures.

Plants are constantly exposed to different environmental stresses such as extreme temperatures, high salinity, excess or lack of water, light and nutrients that strongly limit plant growth and significantly reduce crop yield. Plants exposed to environmental stress exhibit various phenotypic symptoms as poor germination, stunted seedlings, chlorosis, reduced leaf expansion and wilting. Plants respond with changes in their pattern of gene expression and protein products when exposed to these stresses. Thus, the ability to adapt has an impact on the distribution of the plant and crop yield. Understanding the mechanism of stress tolerance and genes involved in the stress signaling network is important for crop improvement. In a proteomic analysis of temperature stress-responsive proteins of Arabidopsis thaliana rosette leaves, an uncharacterized protein, known as salt-tolerant related protein (STRP), resulted to be strongly increased by cold treatment. The aim of this work was to clarify the role of this protein in Arabidopsis response to cold stress. By using polyclonal antibodies obtained against recombinant STRP protein, it was demonstrated that STRP is expressed in the cytosol but is also associated to the plasma membrane. Low temperature treatment greatly increased STRP levels in the cytosol and this effect was due to an enhanced protein stability rather than to activation of gene transcription. Moreover, STRP knock out mutant showed increased susceptibility to oxidative damage induced by cold stress, as demonstrated by the higher levels of lipid peroxidation and ion leakage. These results suggest that STRP may play a protective role in the plant response to cold stress.