THE PRIMARY DEFECT IN DEVELOPING SEED FROM THE HIGH OLEATE VARIETY OFPEANUT (ARACHIS-HYPOGAEA L) IS THE ABSENCE OF BETA(12)-DESATURASE ACTIVITY

A high oleate mutant variety of peanut, F435, has been identified whic h has a seed oil containing 80% oleate and less than 2% linoleate (A.J . Norden et al. Peanut Sci., 14 (1987) 7-11). This trait shows single gene inheritance in some genetic backgrounds (K.M. Moore and D.A. Knau ft, J. Hered., 80 (1989) 252-253). The DELTA12-desaturase is the enzym e which catalyzes the conversion of oleate to linoleate, the first ste p in the biosynthesis of polyunsaturated fatty acids. The high oleate trait in variety F435 may result from a defect in this activity. In th e present report, the DELTA12-desaturase activity in microsomes from d eveloping peanut seed from the parent variety F78-1339 and the mutant variety F435 are compared. The activity in developing peanut seed micr osomes is unusually stable with a half-life of about 5 days at 0-degre es-C. The specific activities of the supplementary components, 1-acyl- 2-lyso-sn-glycero(3)phosphocholine:acyl-CoA acyl transferase and cytoc hrome b5 reductase and the concentrations of cytochrome b5, required f or DELTA12-desaturase activity, were compared in normal and mutant mic rosomes. These components were present in nearly equivalent concentrat ions and activities. The high oleate trait in developing peanut seed v ariety F435 is associated with a major decrease in the activity of the DELTA12-desaturase with no changes in other activities associated wit h the DELTA12-desaturase.