Trading common plant defences for metal accumulation New insights into the evolution of metal hyperaccumulation as a defence against diseases in plants could be useful for agricultural and bioremediation technologies. Climate Change and Environment © Shutterstock The Noccaea caerulescens plant is a hyperaccumulator of heavy metals, and seems to have evolved this trait to defend itself against pathogens. It also appears to have lost the ability to use defence mechanisms common to most plants, suggesting a trade-off. The EU-funded TRADEOFF METAL (Trade-offs in immunity in the metal hyperaccumulator Noccaea caerulescens) project aimed to study the processes involved in the gain of metal hyperaccumulation and loss of other defensive traits in N. caerulescens. The first step was to identify individual plants that exhibit signs of the trade-off. Researchers exposed plants to high and low concentrations of zinc, as well as a pathogen. Individual plants were then classified according to their ability to accumulate zinc and to exhibit common defence responses to the pathogen, such as cell death. They found that plants exposed to high levels of zinc were more resistant to pathogens, and those grown on low levels more susceptible. Plants with reliably reproducible differences were selected for further analysis. This involved identifying the genes involved in the trade-off between metal hyperaccumulation and inducible defences. The evolutionary information gained is useful for understanding how species adapt and persist in fragmented or damaged habitats such as industrial sites. TRADEOFF METAL's findings also shed light on how plant responses to biotic and abiotic stressors may be connected at the molecular level. Practically, this research can inform crop improvement strategies as well as efforts to clean up heavy metal pollution through phytoremediation. Keywords Metal hyperaccumulation, Noccaea caerulescens, pathogens, TRADEOFF METAL, immunity
