Omics approaches for understanding heavy metal responses and tolerance in plants

Abstract

Recent years have witnessed a gradual increase in the bioavailability and groundwater leaching of toxic heavy metals (HMs) in the environment, driven mainly by anthropogenic invasions. HMs, especially ranked as toxic/carcinogenic non-essential ones including Cadmium (Cd), Arsenic (As), Aluminium (Al), Mercury (Hg) and Lead (Pb) have emerged as the major soil, air and water contaminants affecting food production, quality and security worldwide. HMs affect plant growth and crop yield. Plants have developed intricate defense mechanisms for safeguarding themselves against the toxic effects imposed by HMs, including compartmentalization and sequestration in cell-organelles, inactivation by complex formation with the organic ligands and their exclusion using transporters, ion channels, transcription factors and signaling molecules, beside others. Omics approaches have generated significant resources and updates on the plant genome, transcriptome and metabolome plasticity against HM-induced stress stimuli. Omics technologies are pragmatic and seen as feasible approaches for characterizing the roles of genomes (genomics), coding (transcriptomics) and non-coding (miRNAomics) RNA transcripts, and metabolites (metabolomics) including metals (metallomics), which can ultimately be used for improving stress tolerance or generating resilience plant systems. This review aims to summarize the current understandings on the mechanistic insights of selected toxic (Cd, As, Al, Hg and Pb) HM-plant interactions, including their uptake, transport, toxicity and chelation/sequestration in cellular components, besides how plants respond and adapt to these stress factors. State-of-the-art in Omics approaches including genomics, transcriptomics, metabolomics, miRNAomics and metallomics for plant HM research have been presented. Present status, challenges and future prospects are also discussed.