When grown in the absence of metal, however, these plants are defenseless against diseases like powdery mildew, a common fungal infection that most other plants fight off with ease.
In most plants, exposure to powdery mildew and other pathogens triggers the plant defense pathway, a series of biochemical events that occur in succession and help the plant resist infection. A molecule called salicylic acid - a common plant compound and the active ingredient in pharmaceuticals like aspirin and acne medications - governs this pathway.
When faced with a fungus or bacteria, most plants turn up their production of salicylic acid, which then interacts with other molecules in the plant, eventually turning on the genes that produce the proteins involved in fighting infection. These infection-fighting proteins also turn off salicylic acid production, a phenomenon known as negative feedback. In this way, plants can turn the pathogen defense pathway on and off as needed.
Most plants maintain very low levels of salicylic acid in their tissues unless they are fighting an infection. Metal hyperaccumulators, however, have significantly elevated salicylic acid in their tissues all the time.
In the current study, Salt and his colleagues compared salicylic acid levels in both the hyperaccumulator Thlaspi and the common lab plant Arabadopsis, which does not accumulate metal. They also compared fungal infection rates in both types of plants when grown with or without exposure to the metal nickel.
They found significantly higher levels of salicylic acid in the hyperaccumulator compared to the non-accumulator. In addition, while Thlaspi thrived in metal-enriched soil, it succumbed to a severe fungal infe