Histone Acetyltransferase GENERAL CONTROL NON‐REPRESSED PROTEIN 5 (GCN5) Affects the Fatty Acid Composition of Arabidopsis thaliana seeds by Acetylating FATTY ACID DESATURASE3 (FAD3).

Seed oils are important natural resources used in the processing and preparation of food. Histone modifications represent key epigenetic mechanisms that regulate gene expression, plant growth and development. However, histone modification events during fatty acid (FA) biosynthesis are not well understood. Here, we demonstrate that a mutation of the histone acetyltransferase GCN5 can decrease the ratio of -linolenic acid (ALA) to linoleic acid (LA) in seed oil. Using RNA-Seq and ChIP assays, we identified FAD3, LACS2, LPP3 and PLAIII as the targets of GCN5. Notably, the GCN5-dependent H3K9/14 acetylation of FAD3 determined the expression levels of FAD3 in Arabidopsis thaliana seeds, and the ratio of ALA/LA in the gcn5 mutant was rescued to the wild-type levels through the overexpression of FAD3. The results of this study indicated that GCN5 modulated FA biosynthesis by affecting the acetylation levels of FAD3. We provide evidence that histone acetylation is involved in FA biosynthesis in Arabidopsis seeds and might contribute to the optimization of the nutritional structure of edible oils through epigenetic engineering. Significance Statement Plant oils represent renewable sources of valuable fatty acids for both chemical and health-related industries. Although fatty acid metabolism has been well characterised, the epigenetic regulation of fatty acid biosynthesis remains elusive. Here we show that histone acetylation of a key fatty acid desaturase affects fatty acid composition in Arabidopsis seeds.