Dissection Of Molecular Basis For Seed Fatty Acid And Stem Epicuticular Wax Biosynthesis Regulated By Histone Acetyltransferase GCN5 In Arabidopsis Thaliana

Fatty acids(FAs)are a kind of carboxylic acid compounds.FAs are the major components of seed oil,which plays an important role in high production,high quality seed oil and maintaining human health.Cuticle wax covers the aboveground surfaces of plants,which could protect the plants from resisting biotic and abiotic stress.Epigenetics,is a research focus and an integration of many independent regulatory mechanisms.In this paper,based on the phenotype screening,we concernd FA metabolism as the core regulation,and found that histone acetyltransferase involved in the biosynthesis of FAs and cuticle wax.The main results obtained are as follows:1.We show that there were significant variation of the FA content and composition in the T-DNA insertion mutants of 17 genes involved in histone acetylation and methylation.Notably,mutation in the histone acetyltransferase GCN5 can decrease the ratio of a-linolenic acid(ALA)to linoleic acid(LA)in seed oil.Through RNA-Seq and ChIP assays,we identify FAD3,LACS2,LPP3 and PLA?? 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 gcn5 was rescued to wild-type levels through the overexpression of FAD3.The results of the present study indicated that GCN5 is invloved in FA biosynthesis by affecting the acetylation levels of FAD3.It provided evidences that histone acetylation is invloved in FA biosynthesis in Arabidopsis seeds,and might contribute to the optimization of the nutrition structure of edible oil through epigenetic engineering.2.We reported that gcn5 mutant had a significantly glossy stem compared to that of wild-type Ws.Scanning electron microscopy revealed that the amount of wax crystal were significantly reduced in gcn5 mutant stem than that in Ws.Combined with RNA-Seq and ChIP data,we characterized three GCN5 candidate genes,which involved in the biosynthesis of epidermal wax,including,CER1-L1,CER26 and CER3.Of them,CER3 encodes a putative acetaldehyde decarboxylase,which catalyses the synthesis of very long chain fatty acid reduction reaction of aldehydes.GC-MS results showed that the total wax load and coverage of individual compound classes were significantly reduced in the gcn5 mutant which is similar with the cer3 mutation phenotype.Further studies proved that,GCN5-mediated H3K9/14ac acetylations of CER3 regulated CER3 expression.Moreover,overexpression of CER3.In gcn5 mutant could increase the total wax load compared to wild-type levels.Our results provided novel insights in the histone acetylation-mediated regulation of cuticle wax biosynthesis in Arabidopsis stem.