Current Research in our Laboratory Focuses on the Following Aspects of Plant Biology:  

1)      The metabolism, metabolic regulation, and genetic manipulation of plant trichome glands.   Key aspects are:

• Basic studies of metabolic capability and regulation in glands  

• Metabolic engineering of glands to enhance natural-product-based pest and disease resistance  

• Metabolic engineering to produce new compounds in glands, e.g. pharmaceuticals, neutraceuticals, food essences, etc.

  2)   Mechanisms of pollutant metal sequestration in plant vacuoles.  Key aspects are:

• Basic studies of tonoplast transporters and their genes 

• Genetic manipulation to enhance plant tolerance to toxic metals

• Genetic manipulation to enhance the plant's potential for phytoremediation of and enhanced tolerance to pollutant inorganic ions.

  3)   Rhizosphere interactions (plant root with soil microbes) leading to enhanced degradation of organic pollutants in soil.  Key aspects are:  

• Identifying compounds produced by plant roots that can accelerate organic pollutant degradation in soil.

• Eventually, genetic manipulation of compound production to enhance phytoremediation potential of suitable plants.

  1)            Trichome Gland Studies  --  In this work we are currently interested in reaching a better understanding of the basic biology of an exudating (secreting) peltate trichome gland system that will allow manipulation to increase natural-product-based pest and disease resistance and will allow glands to be used as a "factory" for producing useful chemicals, including pharmaceuticals, neutraceuticals, natural-product pesticides and antibiotics, flavor and aroma compounds, cosmetic ingredients, etc. (molecular farming).  Peltate trichome glands are aggregates of 1 to 9 specialized cells suspended on a stalk above the aerial surfaces of many plants.  Exudates from glands can move to the plant surface where they are thought to serve the plant as a first line of defense against insect or microbe predation.  

                   Certain plants produce as much as 30% of leaf dry weight as trichome exudate (16% in the experimental plant that we work with).  This translates to up to perhaps 200 kilograms of exudate per hectare.  Such massive production capacity makes this system a realistic one for molecular farming, particularly since exudate is on the plant surface and can simply be removed by washing with an appropriate solvent.  Since macerating the tissue is not required to recover exudate, compounds are recovered in highly pure form.  And, the remainder of the plant might be used for another purpose.  Thus, two or more molecular farming products might be recovered from one crop.  

           In addition to studying the metabolism of glands, we are currently engaged in genetic manipulation of glands to provide enhanced, natural-product-based disease resistance (on the plant).  Also we are beginning to introduce genes from endangered or threatened species (e.g. reef corals) into glands to lay the groundwork for using plants to produce pharmaceutically active compounds currently obtained by harvesting such species.  We are also studying compounds that may be produced by epidermal cells which confer resistance to certain fungi.

     2)            Mechanisms of Pollutant Ion Sequestration  --  In this work we are focusing on transporters that remove excess pollutant metals (Cd, Zn, Mn, Hg, etc.) from the cytosol to the vacuole.  The higher plant vacuole is a largely non-metabolic compartment where potentially toxic compounds and ions are sequestered.  Recent results show that transport proteins called antiporters exchange protons in the vacuole for  metal ions to cause accumulation of the metals in the vacuole, thus removing them from the cytosol, a more toxicity-sensitive compartment.  Enhancing the number or ion selectivity of these transporters could enhance tolerance in the plant.  And, increased vacuolar accumulation potential might also be important in enhancing phytoremediation potential.  Phytoremediation (cleaning) of soils containing inorganic pollutant ions requires that the plant have a high capacity to take up and sequester of the pollutant and be tolerant to these high levels.  The pollutant-filled plant is then harvested, dried, and combusted to yield concentrated pollutant for recycling, and a cleaned soil.  The cost of cleaning sites in the U.S. contaminated with toxic and radioactive metals using conventional methods (excavate/re-bury) is currently estimated to be about 300 billion dollars.  Phytoremediation may provide a low-cost alternative in many sites.  

           We are currently doing collaborative research (with Dr. K. Herschi, Baylor University) using genes for vacuolar transporters that can enhance Cd, Zn, Mn accumulation in plants.  These studies are testing the exciting possibility that enhanced tolerance and phytoremediation potential may be achievable by genetic engineering of transport proteins.    

3)            Rhizosphere Interaction in Organic Pollutant Degradation  -  A relatively new project in the lab involves the characterization of compounds produced by roots that may stimulate degradation of organic pollutants, e.g. DTT, PCB in contaminated soil.  The costs of remediating this pollution problem in the U.S. is estimated to be about 3 billion dollars.  Phytoremediation of organic pollutants currently represents a very small (~0.2%) contribution to the solution because we know so little about how organic pollutants are degraded in the rhizosphere and how plants may contribute.  But, it is known that the presence of plants and fungi can accelerate pollution breakdown.  We have begun to study this problem in collaboration with a private company that does field evaluation of  organic pollutant phytoremediation.  Our long-term goal in this work is to determine which compounds are produced by field-proven plants that can significantly enhance organic pollutant breakdown.  Then we will seek to manipulate the plant to enhance production of these and related compounds to enhance phytoremediation potential.  Our first publication on this subject was recently submitted.

Loughrin, J.H., and G.J. Wagner.  Compounds in the rhizosphere surrounding perennial ryegrass roots:  Implications for bioremediation.  Submitted.

Dr. George J. Wagner

Professor, Department of Agronomy

University of Kentucky - Lexington, KY  40546-0091

Office:  200L Tobacco and Health Research Institute

Telephone:  859-257-5974 ; Fax:  859-323-1077

Email: gwagner@ca.uky.edu