Email: parkash@psis.umass.edu
O. Parkash's Plant Soil and Insect Sciences Web Site

Ph.D.: Durham University, Durham, England (U.K.) 1998
Postdoctoral Training: Dept. of Genetics, University of Georgia, Athens

My research program is focused on the phytoremediation of toxic pollutants with the purpose of environmental clean up of contaminated soil, water and air. Phytoremediation- a plant-based technology is a new and exciting field of plant biology and it demonstrates the great potential of plant biotechnology to be used for environmental restoration. My research approach involves a multidisciplinary application of methodologies from molecular biology, genomics (cloning of genes conferring detoxification or tolerance, ion transport and sequestration), physiology and biochemistry to decipher the underlying molecular mechanism of metal tolerance. My recent research has been focused mainly on the detoxification and remediation of toxic metalloids and metals such as As and Cd, using genetically engineered plants. I am extending my research on other toxic metals such as Pb and Cr. Following are the currently ongoing projects in my lab:

1. We have genetically engineered plants for phytoremediation of arsenic by overexpressing two bacterial genes, arsenate reductase (ArsC) and gamma-glutamyle cysteine synthetase (g-ESC). These plants are highly resistant and hyperaccumulated 3-fold more arsenic in the aboveground tissues. This research was published in a high profile journal Nature Biotechnology (Dhankher et al., 2002). This paper is the first proof of concept for remediation of arsenic contaminated soil or water by engineered plants. My research work on arsenic phytoremediation was discussed and written by other researchers in many journals. It was in headline news in more than 1000 national and international newspapers (e.g. USA Today, Salt Lake Tribune, Try-City Herald, Augusta Chronicles, Athens Banner Herald, Macon Chronicles, Sun Sentinels (USA), The Ottawa Citizen (Canada), Le Monde (France), Indian Express, Central Chronicles (India) etc.) and science magazines (e.g. The Scientist, National Geography, Science Daily, MIT Technology Review, Geotime, La Recherche (France), Down to Earth, Terragreen etc.). It was also featured in headlines on National Geographic Channel, ABC (Australian Broadcast Corporation), Reuters, Science News bulletin Indian TV etc. This work has helped to open up a new area of phytoremediation research. It demonstrates that engineering plants with multiple transgenes can be used to get a synergistic effect that transcends what either gene could accomplish on its own. It also revealed the potential to use plant genetic engineering for a new application that could have a major positive impact on the environment.

We are cloning more genes that can further enhance As tolerance and hyperaccumulation in shoot tissues. We will develop and transfer these arsenic phytoremediation strategies in fast growing high biomass accumulating plants for field trials. For efficient phytoremediation of arsenic, it is important to engineer fast growing high biomass plants with less agronomic requirements. It is also equally important that engineered crop plants should not be food crops and easily distinguishable even by layman in order to avoid accidental human exposure. We have selected Crambe species (a member of Brassica family) an ideal crop for subsurface arsenic phytoremediaon. It is cultivated in many parts of world as a non-food crop, mainly for industrial oils used in lubricants, additive in synthetic rubber, adhesives and electrical insulation. It can be rotated with rice crop and well suited for Indian sub-Continent where arsenic pollution is widespread. We are developing a transformation method and engineering Crambe for arsenic detoxification and sequestration.

2. We are also extending phytoremediation approach to other heavy metals such as Cd, Cr and Pb. We will search and amplify many other potential genes for heavy metal tolerance and detoxification from the fully sequenced Arabidopsis and rice genomes. We would like to try these plant and other bacterial genes for their possible role in detoxification and remediation of heavy metals and metalloids.

3. We are developing a research program on crop improvement for enhancing human health. In this we will conduct research on the fundamental aspects of plant mineral ion transport such as Zn, Fe, Ca, PO4, enhancing their uptake in plants and reducing the uptake of toxic metals such as Cd, Cu, Ni, Pb, Cr, As, and Hg in plants to prevent the entry of these toxic metals into the food chain in order to improve human health. We will use existing data bases and work with collaborators to identify genes that control mineral nutrient uptake and stress tolerance, and will engineer crop plants using both forward and reverse genetics strategies in order to enhance and/or block the uptake of nutrient and toxic ions.

Significance of Phytoremediation research:

Heavy metals and metalloids such as mercury, lead, cadmium chromium, and arsenic are extremely toxic and adversely affect the health of millions of people worldwide. More than 400 million people are at the risk of arsenic poisoning in Bangladesh and West Bengal state of India due to high level of arsenic contamination in drinking water and soil. Department of Energy (DOE) and other government and industrial sites in the U.S. are heavily contaminated with mercury, arsenic, and other toxic metals such as cadmium, copper, chromium, lead, and zinc. Hundreds of Superfund sites in the United States are listed on the National Priority List (NPL) (www.epa.gov/superfund/sites/nl/info.html) as having unacceptably high levels toxic metals and are recommended for cleanup. In the majority of cases, these sites are not cleaned up because the cost in both dollars and environmental damage is too high. Physical remediation methods involving soil removal and burial are expensive, impractical on the scale that is needed, and environmentally destructive. Phytoremediation, a plant-based technology, offers a cost-effective and environment friendly alternative to physical methods. Higher plants can extract pollutants from the soil or water through their normal root uptake of nutrients and can store/concentrate pollutants in their cells and/or convert toxic pollutants to less toxic forms. Phytoremediation strategies for heavy metals rely on plant roots to extract, plant vascular systems to transport, and leaves to act as sinks to concentrate metals above-ground for harvest and processing.

Representative publications:

Anne Marie, Om Parkash Dhankher , Bonnie McCaig and Richard B. Meagher. Ancient classes of plant metallothioneins bind nutrient and toxic metals differentially. Plant Mol. Biology , 2005 (in press)

Om Parkash Dhankher and J.A. Gatehouse. Tissue-specific and developmental regulation of stress-induced Pisum sativum HSP70 promoter in transgenic tobacco. Physiol. Mol. Biol. Plants 10(1): 49-58 (2004) (with cover page).

Yujing Li, Om Parkash Dhankher, Laura Carreira, David Lee, Julian Schroeder, Rebecca Balish, and Richard B. Meagher. Overexpression of phytochelatin synthase in Arabidopsis leads to enhanced tolerance to arsenic and cadmium sensitivity. Plant Cell Physiology 45(12): 1787-1797 (2004).

Anne Marie, Om Parkash Dhankher, Bonnie McCaig and Richard B. Meagher. Ancient classes of plant metallothioneins bind nutrient and toxic metals differentially. Plant Mol. Biology, 2005 (in press)

Om Parkash Dhankher, Barry P. Rosen, Mark Fuhrmann and Richard B. Meagher. Increased cadmium tolerance and accumulation by plants expressing bacterial arsenate reductase. New Phytologist 159(2): 431-441 (2003).

Om Parkash Dhankher and J.A. Gatehouse. Non-systemic induction of polyphenol oxidase in pea and chickpea after wounding. Physiol. Mol. Biol. Plants 9: 125-129 (2003).

Om Parkash Dhankher, Yujing Li, Barry P. Rosen, Jin Shi, David Salt, Julie F. Senecoff, Nupur A. Sashti and Richard B. Meagher. Engineered tolerance and hyperaccumulation of arsenic in plants by combining arsenate reductase and g-glutamylcysteine synthetase expression. Nature Biotechnology 20(11): 1140-1145 (2002).

Om Parkash Dhankher, J.E. Drew and J.A. Gatehouse: Characterization of a pea hsp70 gene which is both developmentally and stress regulated. Plant Molecular Biology 34: 345-352 (1997).

Om Parkash Dhankher and N.K. Matta: Effect of salinity on storage proteins of Chickpea (Cicer arietinum L.) seeds. J. Plant Science Research 8: 74-76 (1992).

Om Parkash Dhankher, Krishna Kumari and N.K. Matta: Qualitative and quantitative studies on seed protein fractions of Vigna unguiculata L.Walp. J. Plant Science Research 6:75-79 (1990).