MOLECULAR DISSECTION OF THE CELLULAR MECHANISMS INVOLVED IN NICKEL HYPERACCUMULATION

Hyperaccumulator plant species are able to accumulate between 1-5% of their biomass as metal. However, these plants are often small, slow growing, and do not produce a high biomass. Phytoextraction, a cost-effective, in situ, plant based approach to soil remediation takes advantage of the remarkable ability of hyperaccumulating plants to concentrate metals from the soil and accumulate them in their harvestable, above-ground tissues (Salt et al., 1998). However, to make use of the valuable genetic resources identified in metal hyperaccumulating species, it will be necessary to transfer this material to high biomass rapidly growing crop plants (Persans and Salt (2000)). These plants would then be ideally suited to the phytoremediation process, having the ability to produce large amount of metal-rich plant biomass for rapid harvest and soil cleanup. Although progress is being made in understanding the genetic basis of metal hyperaccumulation (Salt and Krdmer, 1999) a more complete understanding will be necessary before we can take full advantage of the genetic potential of these plants. Research funds provided by the DOE EMSP (DE-FG07-98ER20295) have been used to start to uncover the genetic processes involved in the hyperaccumulation of Ni in Thlaspi goesingense. Our strategy has focused on isolating and characterizing the key genetic information needed for expression of the metal-hyperaccumulation phenotype. In the last reporting period we determined that nickel tolerance was the key difference between the hyperaccumulator T. goesingense and the non-accumulator Thlaspi arvense. We also established that this nickel tolerance was primarily due to an enhanced ability to compartmentalize Ni in the leaf cell vacuoles of the hyperaccumulator. During the 2000-2001 reporting period we have been investigating the molecular genetic mechanism of this enhanced vacuolar accumulation of Ni in the hyperaccumulator