Mechanisms of heavy metal resistance in Silene vulgaris

A few plant species, like Silene vulgaris, have evolved ecotypes, that are capable of growing on metal-enriched soils. These tolerant ecotypes exhibit metal-specific resistance mechanisms, which are not completely understood to date. Resistance to copper, zinc and cadmium seems to be regulated by different major genes and some hypostatic modifiers. Metallothionein (MT2b) expression is involved in the level of copper tolerance, while an enhanced ATP-dependent copper efflux across the root cell plasma membrane may result in a decreased copper-accumulation and contributes to the higher resistance of mine plants compared to the copper-sensitive plants. Given the lack of evidence for the significance of similar strategies for zinc and cadmium (such as reduction of uptake and increased binding to intracellular molecules) vacuolar compartmentation is generally believed to be the basic mechanism of tolerance of zinc and cadmium in higher plant species. An enhanced tonoplast transport of zinc in roots plays a role in zinc tolerance, but the existence of a similar tolerance mechanism for cadmium remains to be demonstrated. In our present research, the use of molecular biological techniques to study the presence and expression of (transporter) genes (like ZAT, ZNT and other families) has been initiated. Introduction