Research Molecular Biologist

Professional Biographical Information:

Ph.D. in Biochemistry (1980), University of Georgia

M.S. in Biology (1972), University of Alabama

B.S. in Secondary Education (1969), University of Alabama

Biology major, Chemistry/Geology minor

1993-present: Research Molecular Biologist; USDA-ARS, Appalachian Fruit Research Station, Kearneysville, WV

1984-1993: Research Molecular Biologist/Chemist; USDA-ARS, Richard B. Russell Research Center, Athens, GA

Description of Research Projects:

The Problem

                Low Temperature extremes and frost:  Among abiotic stresses impacting fruit tree productivity, acute freeze damage can be one of the worst, sometimes eliminating entire orchards and resulting in significant fruit tree losses.  Even trees that survive freezing temperatures have reduced vigor, longevity, and productivity. It was estimated that in New York State alone 25,000 apple trees were lost to winter damage in 2003-2004 at a valued cost of 2.5 million dollars.  Damage to fruit production does not always require low temperature extremes. Frost formation on developing flowers damages the female reproductive organs and prevents pollination and subsequent fertilization; no fruit can be produced without these processes. We are all too familiar with examples of killing frosts which limit citrus production as far south as Florida and which in the past have severely impacted the peach industry.   

                Lack of adequate water: Water is commonly the most limiting environmental factor for crop survival and growth, and even short term water shortages can have significant effects on plants by weakening them and making them more susceptible to damage from other factors like disease and insects.  The effects of limited water availability can be especially detrimental to tree growth in environments where inadequate soil volumes, soil compaction, and elevated or sub-zero temperatures can combine to increase tree moisture stress. Since these conditions can be found in many US orchards, growers have adopted cultural practices to minimize the impact of water stress on tree survival and growth, including supplemental irrigation, training systems, mulching, and the use of dwarfing rootstocks. Despite these measures, adverse weather conditions still significantly affect production.  For example, US apple production in 2002 declined by 4% from 2001 production due in part to drought conditions experienced in several regions of the country.  Annual losses due to both low temperature and drought stress for all crops in the US are estimated to be nearly one billion dollars. 

My long-term research goals are 1) to characterize the regulation of genes that respond to different environmental (abiotic) and disease (biotic) stresses in order to understand which genes respond and how their response protects the tree from damage, and 2) to develop novel strategies based on this information to prevent stress damage and enhance fruit tree performance under adverse conditions.  One of the specific aims of this research is to minimize losses in tree productivity under less-than-ideal conditions in the field.  The main focus is on protecting apple and peach trees from severe weather conditions, such as freezing and drought.  Another aim of the research is to utilize biotechnology in solving tree productivity problems during exposure to extremes of temperature and water limitations. 

Providing protection from frost damage to developing flowers:

To this end I am working to develop tissue-specific constructs for transforming cold-protective genes into apple and peach.  The result will be expression of cold-protective genes only in flowers where most of the frost damage occurs.  These genes will provide protection to the frost-sensitive flowers in the event of an untimely frost.  Among the genes we will test for cold-protective activity are different members of the family of dehydrins.  The proteins encoded by these genes are thought to protect other cellular proteins from cold damage by physically interacting with them.  This project relates to ARS Strategic Goal 1 (genes that enhance an organism’s ability to adapt to its environment).

Collaborators:

Dr. Michael Wisniewski, Supervisory Plant Physiologist, USDA-ARS, Kearneysville, WV

Dr. Timothy Artlip, Microbiologist, Support Scientist, USDA-ARS, Kearneysville, WV

Identifying peach genes that respond to cold or short days:

In previous experiments we identified nearly 50 genes that likely contribute to a fruit tree’s ability to cold acclimate.  One of these genes is a new peach dehydrin (dehydrin 3) whose structure is similar to that of the drought-responsive peach dehydrin 2, but whose pattern of expression is more like that of the cold and seasonally regulated peach dehydrin 1.  We plan to characterize the tissue-specificity of its expression, since colleagues at Clemson University have also isolated it from a mature peach fruit EST library.  Another gene we plan to characteriza encodes an mRNA binding protein.  These proteins can physically associate with specific mRNAs and have been shown to be responsive to cold treatments in other plants.  We hope to identify the mRNAs bound by this protein, and determine if the protein protects the stability of the mRNA or if it enhances its translatability some other way.  mRNAs have complex secondary and tertiary structures which can block translation into proteins; formation of some of these structures is highly dependent on temperature, with low temperatures favoring stability of the structures.  Determining how this gene contributes to cold acclimation will lead to the development of a strategy to improve its effect on cold-treated tree fruit.  These studies are linked to ARS Strategic Goal 1.       (Figure 1)

Collaborators:

Dr. Michael Wisniewski, Supervisory Plant Physiologist, USDA-ARS, Kearneysville, WV

Dr. Timothy Artlip, Microbiologist, Support Scientist, USDA-ARS, Kearneysville, WV

Dr. John Norelli, Research Plant Pathologist, USDA-ARS, Kearneysville, WV

Dr. Robert Farrell, Jr., Assistant Professor of Biology, Penn State Univ, York, PA

Dr. Jenny Renaut, Centre de Recherche Public - Gabriel Lippmann, GD Luxembourg

Dr. Larry Gusta, Professor, Crop Sciences, University of Saskatchewan, Saskatchewan, Canada

Dr. Margaret Pooler, Research Geneticist, USDA-ARS,  US National Arboretum, Washington, DC

Identifying apple genes that respond to water-limiting conditions:

The specific aims of this research project are 1) to identify genes from apple trees with altered expression in response to drought-like conditions using suppression subtractive hybridization, 2) to analyze wild apple seedlings collected from xeric regions in Kazakhstan to identify genes adapted to drier environments, and 3) to exploit current knowledge of genes regulating root development in other plants to enhance root production in apples with the aim of creating more drought-tolerant plants having better soil anchorage.  The first two aims require the identification and manipulation of genes specifically associated with development of drought tolerance.  Analysis of the spatial (i.e. tissue specificity) and temporal (i.e. timing) patterns of expression of drought-protective genes will allow us to select those for further manipulation to improve drought tolerance of fruit trees and maintain their productivity.  The third aim will result in the creation of constructs expressing an apple transcription factor that regulates genes controlling root development.  The constructs will be tested in model plants first, and then assayed in apples to determine how the roots are affected and whether the effects are beneficial to the development of drought tolerance and stronger trees. This aspect of our research is related to ARS Strategic Goal 5, section on decreasing the amount of irrigated water required for orchard survival by increasing the efficiency of water usage by crops.

 (Figure 2)

Collaborators:

Dr. Michael Wisniewski, Supervisory Plant Physiologist, USDA-ARS, Kearneysvill, WV

Dr. Tim Artip, Microbiologist, Support Scientist, USDA-ARS, Kearneysville, WV

Dr. Robert Farrell, Jr., Assistant Professor of Biology, Penn State Univ, York, PA

Identifying genes in fruits responsible for induced resistance to postharvest disease organisms:

Previous work in this area by others has shown that short exposure or fruits and vegetables to UV light provides protection from a number of diseases associated with storage after harvest.  The major limitation of this phenomenon is that it only provides protection for a short time.  If we could find a way to increase this “window of protection” against postharvest diseases, we could significantly reduce fruit and vegetable losses that occur during storage and shipment to market.  To understand how UV exposure results in resistance to disease, we plan to identify genes that are both up- and down-regulated immediately after UV treatment.  Others have shown that a number of defense-related genes are up-regulated in response to UV, but little attention has been focused on genes suppressed by the treatment.  These latter genes may be of great significance, since they are believed to delay ripening of the fruit which also delays disease progression.  This project will be submitted to NSF for funding.

Collaborators:

Dr. Clauzell Stevens, Professor, GW Carver Experiment Station, Tuskegee, AL

Dr. David Mitchell, Professor of Carcinogenesis and Biologist, University of Texas, MD Anderson Cancer Center, Smithville, TX

Dr. Charles Wilson, Plant Physiologist, USDA-ARS, Kearneysville, WV

Other research projects:  A project related to water-limiting studies involves elevating the expression of a specific apple gene to control root development.  Expression of this gene is predicted to increase root length and mass, thus potentially increasing the efficiency of obtaining soil water and enhancing the anchorage of the trees.  An additional benefit may be to increase the tree’s tolerance to high salinity conditions.  (Figure 3)  

            I am also developing an organ-specific construct containing the promoter for a photosynthetic gene to direct expression into fruit tree leaves, while preventing expression in edible fruit.  As a proof of concept study, the construct containing a reporter gene under control of the promoter was transformed into cherry tomato plants.  As expected, expression of the reporter gene was high in leaves and young (green) fruit, but nearly absent in mature (red) fruit.  (Figure 4)

Collaborators:

Dr. Herb Aldwinckle, Professor of Plant Pathology, Cornell University, Geneva, NY

Dr. Ilga Winicov, Retired, Research Professor, Biology, Arizona State University, AZ

Dr. Ann Callahan, Geneticist, USDA-ARS, Kearneysville, WV