Thlaspi caerulescens es una pequeña planta que medra en los suelos ricos en cinc cercanos a minas en Europa y Gran Bretaña. Se sabe que acumula cinc, níquel y cadmio en grandes cantidades, pero el por qué de este hecho era un misterio.
Ahora, científicos de la Universidad de Oxford han demostrado que cuando las plantas de Thlaspi acumulan metales en sus hojas, se vuelven resistentes frente a la bacteria Pseudomonas syringae pv. maculicola.
Los investigadores han demostrado también que las bacterias aisladas de las hojas de plantas procedentes de una antigua mina galesa de plomo y cinc, tienen una mayor tolerancia al cinc que las bacterias aisladas de suelos normales. Esto demuestra que tanto la planta como el patógeno se adaptan para sobrevivir en ambientes ricos en metales, y que los patógenos se adpatan para superar las defensas de la planta. Según Gail Preston, coautor del estudio, 'los metales pesados podrían ser parta de una 'carrera armamentista' entre las plantas y los microorganismos que intentan colonizarlas'.
Esta planta ha sido propuesta para la fitoremediación de suelos contaminados por cadmio.
An unusual wildflower that accumulates metals in its leaves has been found to use them as a kind of 'armour' against bacterial infection.
Thlaspi caerulescens is a small plant that grows on metal-rich soils scattered around Britain and Europe, such as the sites of former mine workings. The plant is known to accumulate zinc, nickel and cadmium to very high concentrations in its leaves, but why it should do this has remained a mystery.
Now scientists from Oxford University have shown that when Thlaspi plants accumulate metals in their leaves they become resistant to attack by the bacterium Pseudomonas syringae pv. maculicola.
The researchers also showed that bacteria surviving on Thlaspi plants on the site of a former lead-zinc mine in Wales had a higher tolerance for zinc than bacteria isolated from plants growing on normal soils. This indicates that both the plant and its pathogens show evidence of local adaptation to survival in metal-rich environments, and that pathogens can adapt to overcome plant defences based on metals. According to Gail Preston, co-author of the study, 'heavy metals may be part of an evolutionary 'arms race' between plants and the microorganisms that try to colonise them.'
This wildflower has been previously proposed for fitoremediation of cadmium polluted soils.
Tomado de /Taken from Science Daily
Fones H, Davis CAR, Rico A, Fang F, Smith JAC, et al. (2010) Metal Hyperaccumulation Armors Plants against Disease. PLoS Pathog 6(9): e1001093.
Metal hyperaccumulation, in which plants store exceptional concentrations of metals in their shoots, is an unusual trait whose evolutionary and ecological significance has prompted extensive debate. Hyperaccumulator plants are usually found on metalliferous soils, and it has been proposed that hyperaccumulation provides a defense against herbivores and pathogens, an idea termed the ‘elemental defense’ hypothesis. We have investigated this hypothesis using the crucifer Thlaspi caerulescens, a hyperaccumulator of zinc, nickel, and cadmium, and the bacterial pathogen Pseudomonas syringae pv. maculicola (Psm). Using leaf inoculation assays, we have shown that hyperaccumulation of any of the three metals inhibits growth of Psm in planta. Metal concentrations in the bulk leaf and in the apoplast, through which the pathogen invades the leaf, were shown to be sufficient to account for the defensive effect by comparison with in vitro dose–response curves. Further, mutants of Psm with increased and decreased zinc tolerance created by transposon insertion had either enhanced or reduced ability, respectively, to grow in high-zinc plants, indicating that the metal affects the pathogen directly. Finally, we have shown that bacteria naturally colonizing T. caerulescens leaves at the site of a former lead–zinc mine have high zinc tolerance compared with bacteria isolated from non-accumulating plants, suggesting local adaptation to high metal. These results demonstrate that the disease resistance observed in metal-exposed T. caerulescens can be attributed to a direct effect of metal hyperaccumulation, which may thus be functionally analogous to the resistance conferred by antimicrobial metabolites in non-accumulating plants.