Metal hyperaccumulation: a model system for coevolutionary studies

Abstract

Recent years have seen a flurry of research activity concerning the hyperaccumulation of heavy metals by plants. Much of the interest in hyperaccumulation has been fueled by the commercial potential of phytoremediation, the use of plants to clean up contaminated soils (Baker et al., 1994; Salt et al., 1995; Chaney et al., 1997, 2000). These applications have in turn spurred many studies of the genetics and physiology of metal uptake (e.g. Krämer et al., 1996; Lasat et al., 1996; Salt & Krämer, 1999; Baker et al., 2000; see also Krämer, 2000; Lombi et al., 2000). Although phytoremediation provides an intriguing and potentially profitable backdrop, the ecology and evolution of hyperaccumulation in natural populations are interesting subjects in their own right. Two papers in this issue (Ghaderian et al., pp. 219–224; Davis & Boyd, pp. 211–217) are exciting contributions to the growing consensus that hyperaccumulation may act as a defense against herbivores and pathogens, and suggest that hyperaccumulation may become a model system for research in this area.

Local adaptation is associated with zinc tolerance inPseudomonasendophytes of the metal-hyperaccumulator plantNoccaea caerulescens

“…Metal-hyperaccumulating plants maintain exceptionally high concentrations of metals in their aerial tissues [1][2][3][4], often exceeding 1% of tissue dry biomass for elements such as zinc, cadmium, nickel and manganese, a phenotype that is thought to protect them from herbivory [5][6][7][8][9][10][11][12] and disease [13][14][15]. There is evidence that the use of metals in defence has led to an evolutionary trade-off between metal hyperaccumulation and some pathogen-induced defences [16][17][18].…”

Spread of metals through an invertebrate food chain as influenced by a plant that hyperaccumulates nickel

“…Several hypotheses have been advanced to explain the evolution of this trait (Boyd & Martens 1992), with most attention focused on the hypothesis that hyperaccumulated metals may act as defenses against herbivory (Boyd 1998;Boyd & Martens 1998;Pollard 2000;Pollard et al 2000). With the exception of recent work by Wall and Boyd (2002), most studies to date have considered interactions between individual plants and herbivores, with little attention paid to the effects of hyperaccumulators on their communities or ecosystems.…”

Nickel in the Environment and Its Role in the Metabolism of Plants and Cyanobacteria

“…In this context it should also be mentioned that hyperaccumulated metals may be spread from hyperaccumulators back into the environment via those herbivores that are not deterred by the high heavy metal content [169]. Since the nickel content accumulated in the plant can easily be controlled by the nickel concentration in the growth medium, hyperaccumulators may be an ideal model for a systematic study of plant-pathogen/herbivore interactions, as discussed by Pollard [170].…”