Molecular and physiological mechanisms of plant tolerance to toxic metals

Authors: MILNER, MATTHEW - Pennsylvania State University; Pineros, Miguel; Kochian, Leon

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 9/5/2013
Publication Date: 1/10/2014
Publication URL: http://DOI: 10.1002/9781118764374.ch7
Citation: Milner, M., Pineros, M., Kochian, L.V. 2014. Molecular and physiological mechanisms of plant tolerance to toxic metals. In: Jenks, M.A. and Hasegawa, P.M., editors. Plant Abiotic Stress, Second Edition. Hoboken, NJ: John Wiley & Sons, Inc. p. 179-196.

Interpretive Summary:

Technical Abstract: Plants have evolved a myriad of adaptive mechanisms based on a number of genes to deal with the different toxic metals they encounter in the soils worldwide. These genes encode a range of different metal and organic compound transporters and enzyme pathways for the synthesis of metal detoxifying ligands. Overall, our understanding of this field indicates that plants have evolved at least two main strategies to deal with toxic metal stress: 1) exclusion of the metal from the plant or from the shoot; and 2) tolerance mechanisms that allow the plant to accumulate or even in some cases hyperaccumulate the metal in the plant. Within these two general metal tolerance strategies, there are a number of variants and subtle adaptations that different plant species have made to adapt to different environmental niches. In this chapter, we provide an overview of these strategies by focusing first on plant tolerance to an essential micronutrient that is also a heavy metal, Zn. We also focus on a toxic metal, Al, which is very abundant in the soil and only becomes a problem to plants when the soil pH drops to pH 5 or below. It is interesting to note that both Zn and Al tolerance appears to depend on the integrated function of metal transporters and the synthesis and transport of metal detoxifying organic ligands. There is still much to be discovered about these tolerance mechanisms, particular with regard to how these processes are regulated and coordinated. Significant progress already has been made that should set the stage for further discoveries, and more importantly, the translation of the knowledge gained from this basic research into the generation of crops that can provide increased yields on metal intoxicated soils while minimizing metal entry into the food chain. Also, these discoveries may also allow for the generation of high biomass plants designed to remediate heavy metal contaminated processes via green technologies such as phytoremediation.