Fatty acid content and composition of Oenothera hookeri seeds containing mutant plastids

The effects of plastid mutations on seed oil content and fatty acid composition are of considerable interest. Seeds of a number of plastome mutants produced by the pm plastome mutator line of Oenothera hookeri were therefore harvested to investigate these effects. The mutants were altered solely in their plastome: each seed lot had the same nuclear background. To facilitate the study, a rapid single‐step method was developed to simultaneously assay both oil content and fatty acid composition of small quantities of Oenothera seed. The lipid analyses showed that the mutated plastome often changed the oil content of the seeds, and that such changes always reduced oil content. Strong negative correlations were observed between oil content and palmitate or γ‐linolenate, and a strong positive correlation was observed between oil content and linoleate. This is the first instance to our knowledge in which plastid mutations have been unequivocally demonstrated to affect seed oil content and composition. Such effects would be indirect, since the mutated plastid genes would not be the structural genes for enzymes on the pathway of oil biosynthesis. The plastid mutations demonstrate another layer of potential complexity in understanding oilseed genetics.