MYB96 stimulates C18 fatty acid elongation in Arabidopsis seeds

Abstract

Very-long-chain fatty acids (VLCFAs) are important precursors of many cellular hydrophobic substances involved in many aspects of plant growth and development. They are synthesized by a microsomal fatty acid elongation (FAE) system through sequential additions of C2 moiety to long-chain fatty acid. While the FAE process has been intensively investigated, its regulatory mechanism remains to be elucidated. Here, we report that the R2R3-type MYB96 transcription factor regulates fatty acid elongation in seeds by directly modulating expression of FAE1, an well-known seed-specific β-ketoacyl–CoA synthase (KCS) that catalyzes the first condensation reaction in VLCFA elongation. The FAE1 gene was up-regulated in MYB96-overexpressing activation-tagging myb96-ox seeds, but down-regulated in MYB96-deficient myb96-1 seeds. Consistently, accumulation of C20 and C22 fatty acids was significantly elevated in myb96-ox seeds, whereas their accumulation was reduced in myb96-1 seeds. These findings suggest that MYB96 directly regulates FAE1 to stimulate C20 accumulation possibly in the regulation of seed maturation and development.