2010 Annual Report
1a.Objectives (from AD-416)
Many plant species produce high amounts of industrially important fatty acids (e.g., hydroxy fatty acids) in their seeds, but the plants generally lack agronomic traits that permit these oils to be produced on a large scale for industrial utilization. The objective of this research program is to discover the genetic basis for the production of these high-value oils and use these genes for production of the oils in robust, non-food crop platforms. Cotton is exceptionally well positioned to serve as a platform for production of high value oils because the main economic driver for this crop is cotton fiber. The seed is generally viewed as a lower valued by-product, and raising the value of the seed through production of industrially important oils would increase farm gate value of the crop and provide society with renewable, sustainable sources of oil that are otherwise obtained from non-renewable petroleum. In addition, high-risk/high-payoff research will be conducted to determine if industrial oils can be produced in vegetative (e.g., leaves and stems) parts of plants. The rationale is that vegetative plant biomass is significantly greater than seed tissues, and by developing methods to produce oil ectopically in leaves and stems, the amount of oil obtained per hectare of land can be substantially increased.
1b.Approach (from AD-416)
Various species and hybrids of Lesquerella will be analyzed to identify genes involved in the production of hydroxy fatty acids. Enzyme functionality will be investigated by expression in yeast cells, and cellular properties will be evaluated through expression in plant cell culture. Candidate enzymes will be expressed in transgenic Arabidopsis, including both developing seed and leaf tissues. Enzyme stability and regulation (primarily by temperature) will be investigated using western blotting and half-life studies. Select genes will be expressed in transgenic cottonseed to evaluate this crop as a platform for production of industrially important oils. Production of hydroxy fatty acids in non-seed tissues will be evaluated in various wild-type and mutant Arabidopsis plants. Documents SCA with University of North Texas. Formerly 5347-21410-004-14S (8/08).
The research activities supported by this agreement are monitored by the ADODR through direct interaction with scientists at UNT (e.g., by site visits), “virtual” lab meetings conducted by teleconference, and extensive and regular emailing by all participants.
In consultation with scientists at UNT, methods were developed at the ARS laboratory for the stable transformation of cotton plants. The end goal is to provide an efficient pipeline for the introduction of value-added traits that can complement traditional breeding studies in cotton. Two different genes were selected for the initial transformation studies based upon their potential for improving the value and/or stress tolerance of cotton. The first gene is an omega-3 fatty acid desaturase (FAD3), which produces a polyunsaturated fatty acid called linolenic acid. The FAD3 gene will be expressed in all parts of the cotton plant. Over-production of linolenic acid in leaves and stems has been correlated with increased drought resistance and improved cold tolerance in other transgenic plants. Linolenic acid is also an essential fatty acid in the human diet, and cottonseed oil typically lacks this fatty acid, but has an abundance of the fatty acid precursor required to produce linolenic acid. As such, over-expression of a FAD3 gene in cotton may improve both agronomic and nutritional characteristics of the plant.
The second gene selected is a diacylglycerol acyltransferase (DGAT) gene isolated from the “burning bush” plant (Euonymus alatus). The oil produced in the seeds of the burning bush plant is unusual and has characteristics that are similar to heavy grade diesel fuel. Notably, the type of oil in burning bush seeds does not have to be chemically modified to produce biodiesel; that is, it can be used directly in combustion engines (provided that enough of the oil could be obtained from seeds, which is not practical on a large scale from burning bush). This novel oil trait is due specifically to the DGAT gene, and expression of the gene in cotton may result in large-scale production of a high-value biodiesel in cottonseed.
In a separate line of research, scientists at the ARS and UNT are investigating the possibility of producing large amounts of oil in the leaves of plants. Certain mutations in the model plant Arabidopsis have been identified that result in a significant accumulation of oil in leaves, and experiments are ongoing to elucidate the underlying mechanisms.