Qing Liu, Craig Wood, Shijiang Cao, Matthew Taylor Shoko Okada, Xue-Rong Zhou, Allan Green and Surinder Singh
Commonwealth Scientific and Industrial Research Organization, Crop Biofactories Initiative, ACT 2601, Australia
Microsomal oleoyl phosphatidylcholine desaturase (FAD2) is largely responsible for the ratio of two major fatty acids, oleic and linoleic acids, together of which accounts for more than 90 % of total fatty acids in safflower seed oil. From safflower, we have isolated the largest FAD2 gene family in plants, with a staggering 11 members with distinct expression patterns and functionalities. The temporal and spatial expression profiles of these genes were revealed through real-time quantitative PCR and their diversified functionalities were demonstrated by ectopic expression in yeast and transient expression in Nicotiana benthamiana leaves. Molecular characterisation of a well-known safflower high oleic spontaneous mutant, termed as ol allele revealed that it was originally derived from progenitor species Carthamus palaestinus through an ancient interspecific hybridization and its subsequent spontaneous mutation by the deletion of a single nucleotide in the coding region of FAD2-1 that resulted in frame shift and nonsense mediated RNA-degradation (NMD). In this high oleic background, RNAi mediated gene silencing targeting the constitutively expressed FAD2-2 produced a seed oil containing 93% oleic acid in seed oil. Biochemical and agronomic performance of selected transgenic lines indicate a promising prospect for commercial exploitation. The high purity of oleic acid in this safflower oil offers an opportunity for manufacturing alternative oleochemicals that are found in the formulation of many hundreds of biodegradable oleochemicals.