Involved in the biosynthesis of dimorphecolic acid (9-OH-18:2(10E,12E)). Catalyzes the formation of the C-9 hydroxyl group and the (E)-delta(10) double bond from the trans-linoleic acid (16:2(9Z,12E)) produced by FAD2-1. Very limited activity with cis-linoleic acid (16:2(9Z,12Z)). Belongs to the fatty acid desaturase type 1 family.