Metal toxicity in rice and strategies for improving stress tolerance

Abstract

Rice (Oryza sativa) is a staple food for the majority of world population. Contamination of rice fields with various types of metals and metalloids causes a serious threat to the cultivation of this crop. Persistent nature and biomagnification potential of metals cause great concerns to the agricultural soils. High concentrations of metals in the soil environment suppress growth, alter metabolism of plants, cause stress and toxicity symptoms, ultimately leading to decreased productivity. To avoid the direct damaging effects of metals, plants have adopted some strategies like binding of metals with the cell wall, organic acids, sequestration of metals within the tissues, etc. Excessive levels of metals in the tissues cause increased production of reactive oxygen species (ROS) which cause oxidative damage to the cellular molecules. To combat oxidative damage due to ROS, plants trigger antioxidant defense mechanism leading to high activities of antioxidative enzymes, increased synthesis of non-enzymic antioxidants and synthesis of stress-related proteins. Overexpression of stress-related proteins and components of antioxidative defense mechanisms can serve as potential strategy for conferring metal stress tolerance in rice plants. Our ever-growing knowledge in the fields of metabolomics, transcriptomics, proteomics, etc., has immensely helped in characterizing the metabolites, transcription factors, and stress-associated proteins involved in metal tolerance of rice plants. © 2019 Elsevier Inc. All rights reserved.