Enhanced Oleic Acid Content in the Soybean Mutant M23 Is Associated with the Deletion in the <i>Fad2‐1a</i> Gene Encoding a Fatty Acid Desaturase

Abstract

Abstract Oleic acid is one of the three major unsaturated fatty acids in soybean oil. Expression of the embryo‐specific Fad2‐1 gene correlates with fatty acid biosynthesis and oil deposition in developing seeds. Elevated levels of oleate in the X‐ray‐induced mutant line M23 have been shown to be associated with the deletion of a Fad2‐1 gene. In soybean, two homologs of the Fad2‐1 gene, termed Fad2‐1a (L43920) and Fad2‐1b (AY611472), presumably encode functional embryo‐specific fatty acid desaturase. The objectives of this investigation were to determine which copy of the Fad2‐1 gene is associated with the increased oleate content in the mutant line and what is the relative transcript abundance of these two embryo‐specific genes. PCR and DNA blot analyses showed that increased oleate content in M23 mutant was associated with the deletion of Fad2‐1a . These results were further validated using five independent soybean populations developed by crossing mid‐oleate and normal‐oleate parents. Investigation of the soybean expressed sequence tag database and reverse transcription PCR analyses revealed that Fad2‐1b is the predominantly transcribed copy of the Fad2‐1 gene. We hypothesize that null mutation in Fad2‐1b in the fad2‐1a mutant background should further elevate the oleic contents of soybean oil.