英国一项最新研究发现，一种草本植物会在叶子中累积大量金属元素，以避免病菌入侵，如同给自己装备了一层“金属铠甲”。
英国牛津大学研究人员在新一期《科学公共图书馆—病原体》上报告说，一种名为遏蓝菜的植物会在叶子中累积高浓度的锌、镍、镉等金属元素，但此前并不清楚它累积金属的用处。
为了解个中缘由，研究人员在不同的金属浓度环境中培养了遏蓝菜，并利用常在萝卜等植物中引发疾病的丁香假单胞菌进行实验。结果显示，不论是锌、镍还是镉，只要遏蓝菜体内金属浓度升高，病菌入侵的程度就会变小。
参与研究的盖尔·普雷斯顿博士说，这表明遏蓝菜是利用环境中的金属元素给自己穿上“金属铠甲”，以抵御病菌入侵。
不过研究人员也发现，在遏蓝菜装备“坚盾”的同时，也有一些细菌进化出了“利矛”。一些在金属矿区发现的细菌已经进化出较高的金属耐受性，因此有可能在具有较高金属浓度的植物体内存活。研究人员说，这就像一场“军备竞赛”，持续地发生在自然界中攻守双方的互动进化中。（生物谷Bioon.com）
生物谷推荐英文摘要：
PLoS Pathog doi:10.1371/journal.ppat.1001093
Metal Hyperaccumulation Armors Plants against Disease
Helen Fones, Calum A. R. Davis, Arantza Rico, Fang Fang¤, J. Andrew C. Smith*, Gail M. Preston*
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.
