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Natural variation, evolution and underlying mechanisms of metal hyperaccumulation in Arabidopsis halleri

Stephan Clemens1, Stephan Höreth1, Deinlein Ulrich1, Kosian Michael1
1 Lehrstuhl Pflanzenphysiologie, Universität Bayreuth

O 2.5 in Biodiversity: Patterns, Function and Protection

11.10.2012, 11:00-11:15, H8

Across nature Zn requirements of thousands of proteins result in comparable Zn quota from bacteria to higher eukaryotes. An extreme exception are Zn hyperaccumulating plants that can show leaf Zn levels of greater than 10,000 µg g-1 dry biomass, i.e. more than 100fold higher than normal plants or most other organisms. This trait is found in populations across Europe irrespective of the metal contamination level of the site. Cd hyperaccumulation on the other hand varies greatly as revealed by our ongoing survey of European A. halleri populations (more than 1000 leaf and soil samples from > 120 sites). We are in the process of analyzing the genotype vs. environmental influence. Metal hyperaccumulation has often been implicated in herbivore defense.

Molecular dissection of metal hyperaccumulation proceeds via RNAi-mediated knockdown of candidate genes identified in comparative transcriptome studies. Key homeostatic processes such as Zn transport and Zn chelation are regulated differently in metal hyperaccumulators. Respective changes in gene expression are seen as key events in the evolution of metal hyperaccumulation. For instance, we found that genes involved in metal chelator synthesis such as nicotianamine synthases (NAS) are important for Zn and Cd hyperaccumulation. On native soil strong AhNAS2 RNAi lines did not reach the Zn hyperaccumulation threshold of 10,000 µg g-1 dry biomass anymore. Leaf Cd accumulation was also significantly reduced.

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last modified 2012-09-21