oil modification

Cotton Industry Seed Quality Goals

In 1994, the cotton industry established six goals for improving cottonseed quality. All goals were set with the understanding that lint yield and quality should not be sacrificed and these will continue to be of greatest economic importance in breeding programs.Increase the overall seed market value. Value is defined as the economic return per unit (either $/acre or $/ton) to the seller of the seed. This is realized through increasing oil and protein content to a minimum base of 18.5 percent each and by maintaining fatty acid and amino acid profiles which are as good as or better than the current varieties.
(From NCPA web page http://www.cottonseed.com)

Cottonseed Fatty Acid Synthesis

Higher plant fatty acid synthesis occurs de novo in the stromal compartment of plastids with a type II, fully dissociable fatty acid synthase complex (FAS). Acyl chains esterified to an acyl carrier protein (ACP) undergo chain elongation by the sequential addition of two-carbon units from malonyl-ACP. Hydrolysis of the acyl-ACP thioester bond by an acyl-ACP thioesterase enzyme terminates acyl chain elongation. The plant acyl-ACP thioesterases are usually categorized by the preference exhibited for their acyl-ACP substrates, specified by the degree of saturation and chain length of the acyl group. The two different types of thioesterases are designated FatA and FatB, with substrate preferences for unsaturated or saturated acyl-ACPs, respectively. Thus, acyl-ACP thioesterases determine the pool of available fatty acids exported from seed plastids for oil assembly. Fatty acid desaturases (Fad), located in the endoplasmic reticulum (ER), then modify the number of double bonds in fatty acyl chains which are incorporated into seed triacylglycerols (TAG).

Modification of Fatty Acid (FA) composition in cottonseed Storage Oils

Our primary goal in cottonseed fatty acid modification (standard cottonseed has 25% 16:0, 15% 18:1, and 55% 18:2) is to develop new edible oils in cottonseed and new industrial oils in cottonseed. To manipulate cottonseed fatty acid composition and produce novel mid-oleic (up to 50% 18:1), low saturate (down to 4% 16:0), and high saturate (up to 65% 16:0) cottonseed oils, we will focus on two key enzymatic steps in the fatty acid biosynthetic pathway. Our metabolic engineering strategy involves targeting the expression of fatB, which likely regulates palmitic acid content and fad2, which likely regulates the proportion of monounsaturated (mostly 18:1) to polyunsaturated (mostly 18:2) fatty acids in cottonseed oil. To develop new industrial oils, we will focus on the expression of heterologous fad2-like proteins (Fad2*) to produce conjugated polyunsaturated fatty acids or epoxy fatty acids. These fad2-like proteins are membrane-bound and appear to act on phospholipids with 18:2 fatty acids esterified at the sn-2 position.

Fatty Acid Modification Strategy:

Metabolic Engineering Approach-- Alter accumulation of saturated and unsaturated fatty acids in seed oil.
Agrobacterium-mediated production of transgenic cotton plants
Development of New Cotton Lines with Different Seed Fatty Acid Compositions-- e.g. Development of “Mid-Oleic” seed

agrobacterium introduction of transgene scheme

fad2 cotton two weeks after transplant

Related Publications

Hemphill, J.K., Maier, C.G.A., Chapman, K.D. 1998. Rapid in-vitro plant regeneration of cotton (Gossypium hirsutum L.). Plant Cell Reports,17(4): 273-279.

Pirtle R.M., Yoder D.W., Huynh T.T., Nampaisansuk M., Pirtle I.L., Chapman K.D. (1999) Characterization of a palmitoyl-acyl carrier protein thioesterase (FatB1) in cotton, Plant Cell Physiology, 40: 155-163.

Yoder D.W., Nampaisansuk M., Pirtle I.L., Chapman K.D., Pirtle R.M. (1999) Molecular cloning and nucleotide sequence of a gene encoding a cotton palmitoyl-acyl carrier protein thioesterase, Biochim. Biophys. Acta, 1446: 403-413.

Chapman K.D., Austin-Brown S., Wessler H., Huynh T., Hoang C., Sparace S., Ricchiuti T., Kinney A., Ripp K., Pirtle I., Pirtle R., Nampaisansuk M., Metabolic engineering for increased cottonseed oleic acid content, Proceedings of the Annual Beltwide Cotton Conferences, National Cotton Council (2001).

Chapman, K.D., Austin-Brown, S. Sparace, S.A., Kinney, A.J., Ripp, K.G., Pirtle, I.L, Pirtle, R.M. (2001) Transgenic cotton plants with increased seed oleic acid content. Journal of the American Oil Chemists’ Society (JAOCS), 78(9): 941-947.

Pirtle, I., Kongcharoensuntorn, W., Nampaisansuk, M., Knesek, J., Chapman K.D., Pirtle R.M. (2001) Molecular cloning and functional expression of the gene for a cotton delta-12 desaturase (FAD2) Biochimica et Biophysica Acta, 1522(2): 122-129.

Huynh, T., Pirtle, R.M., Chapman, K.D. (2002) Expression of a Gossypium hirsutum cDNA encoding a FatB palmitoyl-acyl carrier protein thioesterase in Eschericia coli. Plant Physiology and Biochemistry, 40: 1-9.

Hoang, C.V. and Chapman, K.D. (2002) Biochemical and molecular inhibition of plastidial carbonic anhydrase reduces the incorporation of acetate into lipids in cotton embryos and tobacco cell suspensions and leaves. Plant Physiology 128 (April): 1417-1427.

Hoang, C.V. and Chapman, K.D. (2002) Regulation of plastidial carbonic anhydrase gene expression in cotton (Gossypium hirsutum, L) seedlings during post-germinative growth. Plant Molecular Biology 49: 449-458.

Bartz R., Li W.H., Venables B., Zehmer J.K, Roth M.R., Welti R., Anderson R.G., Liu P., Chapman K.D. (2007) Lipidomics reveals adiposomes store ether lipids and mediate phospholiid traffic, J. of Lipid Research (in press).