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ARS Home » Southeast Area » Raleigh, North Carolina » Soybean and Nitrogen Fixation Research » Research » Publications at this Location » Publication #195347
Title: A MUTATION IN A 3-KETO-ACYL-ACP SYNTHASE II GENE IS ASSOCIATED WITH ELEVATED PALMITIC ACID LEVELS IN SOYBEAN SEEDS

Author
item AGHORAM, KARTHIK - NC STATE UNIV
item Wilson, Richard
item Burton, Joseph
item DEWEY, RALPH - NC STATE UNIV

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/24/2006
Publication Date: 10/2/2006
Citation: Aghoram, K., Wilson, R.F., Burton, J.W., Dewey, R.E. 2006. A mutation in a 3-keto-acyl-acp synthase ii gene is associated with elevated palmitic acid levels in soybean seeds. Crop Sci. 46:2453-2459.

Interpretive Summary: Palmitate is the main component of saturated fat in soybean oil, usually about 11 % of total seed oil content. It is also the fat that contributes to coronary heart disease. Several genes been shown to control the content of this fat in soybean. One of these genes has mutated to a form, called fap2, and causes a higher level of palmitate in soybean seeds. The cause of the mutation was determined by comparing the DNA of fap2 with the DNA of the normal gene. This led to the development of a marker that can be used to easily distinguish plants that have the mutant gene from plants that do not have the gene. This will be useful for plant breeding activities aimed at changing palmitate content of soybean seed oil.

Technical Abstract: Palmitic acid is the major saturated fatty acid component of soybean [Glycine max, (L.) Merr.] oil, typically accounting for ~11 % of total seed oil content. Several genetic loci have been shown to control the seed palmitate content of soybean. One such locus, fap2, mediates an elevated seed palmitate phenotype. Previous biochemical studies indicated that the fap2 locus is associated with a reduction in the activity of 3-Keto-Acyl-ACP Synthase II (KAS II), an enzyme that initiates the elongation of palmitoyl-ACP to stearoyl-ACP in the plastid. The objective of the present research was to define the molecular basis by which the fap2 locus increases seed palmitate levels. We isolated two closely related, yet unique KAS II cDNAs, designated GmKAS IIA and GmKAS IIB, from soybean cultivar Century (Fap2, Fap2) and its derivative high palmitate germplasm C1727 (fap2, fap2). The GmKAS IIB cDNAs recovered from Century and C1727 were identical. In contrast, a single base pair substitution was found in the GmKAS IIA gene from C1727 versus Century which converted a tryptophan codon into a premature stop codon, a mutation that would be predicted to render the encoded enzyme nonfunctional. Knowledge of the DNA sequence polymorphism led to the development a facile, robust cleavage amplified polymorphic sequence (CAPS) marker that readily distinguishes the mutant GmKAS IIA gene. This marker faithfully associated with a second independent germplasm line bearing the fap2 locus, and thus may be useful in breeding programs that target the development of high palmitate soybean cultivars.