Intraspecific variation of metal preference patterns for hyperaccumulation in Thlaspi caerulescens: evidence from binary metal exposures.

Metal preferences with regard to accumulation were compared between populations of the heavy metal hyperaccumulator Thlaspi caerulescens, originating from calamine, serpentine and non-metalliferous soils. Plants were exposed for 3 weeks to factorial combinations of concentrations of different metals in binary mixture in hydroponics. The nature and degree of the interactions varied significantly between populations. In the calamine, non-Cd/Ni-hyperaccumulating population, La Calamine, there were no one-sided or mutual antagonistic interactions among the metals with regard to their accumulation in the plant. In three other populations capable of Cd and Ni hyperaccumulation, from calamine, serpentine and non-metalliferous soil respectively, there were one-sided or mutual antagonistic interactions between Cd and Zn, Cd and Ni, and Ni and Zn, possibly resulting from competition for transporters involved in uptake or plant-internal transport. Significant synergistic interactions, probably resulting from regulation of transporter expression, were also found, particularly in the La Calamine population. All the populations seemed to express a more or less Zn-specific high-affinity system. The serpentine and the non-metallicolous populations seemed to posses low-affinity systems with a preference for Cd and Zn over Ni, one of which may be responsible for the Ni hyperaccumulation of the serpentine population in its natural environment. The calamine population from Ganges also seemed to express a strongly Cd-specific high-affinity system which is in part responsible for the Cd-hyperaccumulation phenotype exhibited by this population in its natural environment. © 2007 The Author(s)

Thlaspi caerulescens, an attractive model species to study heavy metal hyperaccumulation in plants.

Studying heavy metal hyperaccumulation is becoming more and more interesting for ecological, evolutionary, nutritional, and environmental reasons. One model species, especially in the era of high throughput genomics, transcriptomics, proteomics and metabolomics technologies, would be very advantageous. Although there are several hyperaccumulator species known, there is no single model species yet. The Zn, Cd and Ni hyperaccumulator species Thlaspi caerulescens has been studied to a great extent, especially for Zn and Cd hyperaccumulation and tolerance. Its physiological, morphological and genetic characteristics, and its close relationship to Arabidopsis thaliana, the general plant reference species, make it an excellent candidate to be the plant heavy metal hyperaccumulation model specie