Different approaches in metabolomic analysis of plants exposed to selenium: a comprehensive review

Numerous benefits related with adequate selenium supply are well-documented in all life domains; the most prominent comprise Se participation in antioxidant defense, chemopreventive activity, and alleviation of heavy metal stress. For higher plants both, favorable and toxic effects were reported, depending on the biological species, total Se concentration and on the variety/distribution of its physicochemical forms. Extensive studies focusing Se pathways and Se impact in plants have been carried out, providing data of high relevance for human health and nutrition as well as in the areas of agriculture, biotechnology, and phytoremediation. The influence of Se has been observed in all “omics” components; among them, metabolomics seems particularly interesting because the products of plant metabolism directly reflect its actual state and closely denote molecular phenotype. It should be emphasized that plant metabolites derived from Se exposure are of interest in clinical applications, in the production of dietary supplements and functional foods. In this review, recent advances in metabolomics studies of Se in higher plants are presented, primarily focusing on analytical methodology and briefly summarizing biological relevance of the obtained results. In the first part, principal research frameworks related with Se-exposed plants are presented and metabolomic approaches used in these studies are introduced. Selenium uptake and biotransformation processes are briefed, emphasizing the complexity of biological pathways and large variety of Se metabolites; analytical speciation schemes are described and located within targeted or semi-targeted approaches. Next, metabolomic analysis of plants affected by Se exposure is addressed; specific attention is given to metabolites related with stress response, and to products of primary and secondary metabolism (amino acids, fatty acids, and their oxidation products, antioxidants, glucosinolates, phenolic compounds, etc.). Finally, few examples of untargeted metabolomics are presented, highlighting multifaceted Se impact in plants. At the end, short conclusions and future prospective are furnished.