Superfund Research Program
Phytoremediation of Pollutants Using Transgenic Plants
Project Leader: Stuart E. Strand
Grant Number: P42ES004696
Funding Period: 2006-2015
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Final Progress Reports
Year: 2008
In 2008 Dr. Stuart Strand and his team of researchers continued to test the ability to degrade trichloroethylene (TCE) in test beds of fullsize poplars genetically modified with rabbit gene for CYP2E1 and exposed to an artificial aquifer contaminated with TCE. These plants have previously been shown to degrade TCE, cisdichloroethylene, and vinyl chloride in closed vessels in the laboratory. In the field, the transgenic poplar leaves contain much higher levels of known metabolites of TCE degradation than the unmodified trees, suggesting that some of the TCE is being taken up and broken down by the transgenic trees. But TCE concentration in the effluent water is lowest in the unplanted bed, and there is no difference between the beds planted with wild type and transgenic poplars. Chloride increases in the soil and groundwater indicate that TCE is being degraded in all test beds. The presence of ethylene in the effluent water suggests that substantial reductive de-chlorination activity is occurring in all three beds, with the highest activity in the unplanted control. The researchers expect that in the next year reductive de-chlorination will decline as electron donor sources are exhausted.
The research group is also seeking to identify the mechanisms that plants use to degrade VOCs. Microarray experiments were conducted with RNA extracts from poplar plants exposed to TCE. Detoxification genes induced by TCE include several putative cytochrome P450s, glycosyltransferases, glutathione S- transferases, and ABC transporters. Induction of these genes most likely is important for conjugation and storage of toxic products. CYP2E1 transgenic poplar also had increased expression of these genes. They are designing primers and probes to confirm the up-regulation of these genes by QPCR.