Metabolomics for crop improvement against salinity stress

In the post-genomic era, increasing efforts have been done to describe the relationship between genome and phenotype in plants. It has become clear that even a complete understanding of the state of the genes, messages, and proteins in a living system does not reveal its phenotype. Metabolites are the main readouts of gene vs environment interactions and represent the sum of all the levels of regula- tion in between gene and enzyme. Therefore, metabolome can be considered as the final recipient of biological information flow. Some metabolites have a very short lifetime and are indicators of specific metabolic reaction and of plant status. Indeed, it is well known that many of them are transformed during specific stresses and involved in plant stress response and resistance. Salinity provides an important example of the effectiveness of metabolic changes in response to stress. In fact, exposure to salinity triggers specific strategies for cell osmotic adjustment and control of ion and water homeostasis to minimize stress damage and to reestablish growth. A ubiquitous mechanism that plants have evolved to adapt to salinity involves sodium sequestration in the vacuole, as a cheap osmoticum, and synthesis and accumulation of compatible compounds, both for osmotic adjustment and oxidative stress protection in the cytosol. Metabolomics has been utilized for the study of plants in response to salinity stress in order to dissect particular patterns associated with stress tolerance. These studies have proven that certain metabolites are present in case of salt-induced met- abolic dysfunction and can act as effectors of osmotic readjustment or antioxidant response. Thus, the presence of particular metabolite patterns can be associated with stress tolerance and could serve as accurate markers for salt-tolerant crop selection in breeding programs