Chinese Violet Cress: Novel Seed Oil Biosynthesis, Storage, and Functionality

Trevor Romsdahl, Xiangjun Li, Fan Huang, Asghar Shirani, Robert E. Minto, Kent D Chapman, Diana Berman, Chunyu Zhang

University of North Texas; University of Nebraska-Lincoln; Huazhong Agricultural University; University of Nebraska-Lincoln; Indiana University - Purdue University Indianapolis; University of North Texas; University of North Texas; Huazhong Agricultural University; ;

The seed oil of Chinese violet cress (Orychophragmus violaceus), a Brassicaceae species native to China, is enriched in novel C24 dihydroxy fatty acids, designated wuhanic acid [7,18-(OH)₂-24:2Δ15,21] and nebraskanic acid [7,18-(OH)₂-24:2Δ15,21]. Genetic and biochemical evidence is most consistent with the biosynthesis of these fatty acids through a pathway involving a conventional FAD2-type hydroxylase and a variation of fatty acid elongation involving extension of a 3-OH C20 intermediate prior to the completion of a complete elongation cycle. This variant pathway, referred to as “discontinuous fatty acid elongation”, is initiated by a divergent FAE1-type 3-ketoacyl-CoA synthase. In addition to their novel route of biosynthesis, wuhanic and nebraskanic acids are stored in Chinese violet cress seeds in high molecular weight triacylglycerol (TAGs) species that contain an extensive network of dihydroxy fatty acids that are cross-linked as estolides. This novel fatty acid storage results in vegetable oil with superior high-temperature lubricant properties relative to castor oil. Efforts are underway to evaluate Chinese violet cress as a new oilseed crop and to develop genetic resources for agronomic improvement of this plant.