Chapter 5 - Metabolomics-Guided Elucidation of Abiotic Stress Tolerance Mechanisms in Plants

Abstract

Plants thriving under abiotic stress conditions implement various strategies to combat the prevailing stress conditions. Abiotic stresses like high salinity; water stress like drought and water logging; temperature extremes such as high, chilling, and freezing temperatures; mineral deficiency; and contamination of the soil with lethal heavy metals disrupt the plant's normal metabolism, physiology, and growth. Among other stress management strategies, reconfiguration of the metabolite status is one of the most adopted stress tolerance mechanism in the plant. Abiotic stress induces multigene response, resulting in specific modulations in primary and secondary metabolite accumulation. Various metabolites, for instance, carbohydrates such as galactinol, gluconate, raffinose, and trehalose; amino acids like proline, glutamate, and asparagine; polyamines like putrescine, spermine, and spermidine; organic acids; flavonoids; intermediates of xanthophyll cycle like carotene, zeaxanthin, violaxanthin, and antheraxanthin; and tricarboxylic acid cycle intermediates like citrate and oxoglutarate, are modulated in response to various abiotic stresses. Among these metabolites, some are upregulated, whereas some are downregulated according to the need of the plant for confronting the prevailing stress conditions. Various metabolomic techniques have been implemented for the metabolomic elucidation of stress tolerance mechanism in plants. Recent advancements in the field of metabolomics provide a window of opportunity to decipher the abiotic stress tolerance mechanism of plants. With the advancement of the metabolomic techniques, identification, characterization, and quantification of both primary and secondary metabolites that are important in abiotic stress tolerance are now becoming possible. The modernization of traditional metabolomic techniques like mass spectrometry and nuclear magnetic resonance together with the combination of chromatographic separation steps is responsible for improved depiction of essential stress-associated metabolites from the complex metabolite profile of plants. The aim of this review is (1) to emphasize on modulation of different metabolites in plants under various abiotic stresses like high salinity, drought, temperature extremes, high light intensity, and heavy metal stress to get an insight into the mechanism of abiotic stress tolerance in plants and (2) to identify the key metabolites having potential role in stress tolerance for the development of stress-tolerant crops by metabolic/genetic engineering using metabolite biomarkers. Taken together the information provided in this article indicates that metabolomic study with the developed identification and interpretation techniques is paving the way for better understanding the complex metabolic pathways and their regulation during abiotic stress conditions. Successful integration of metabolomics with other “omics” studies will allow to effectively use the knowledge of metabolomics gained to generate stress-tolerant crops.