The seed‐specific transcription factor DPBF2 modulates the fatty acid composition in seeds

Abstract

Triacylglycerol (TAG), an ester derived from glycerol and three fatty acids (FAs), is synthesized during seed development and controlled by transcriptional regulation. We examined the mechanism regulating the FA composition of developing <i>Arabidopsis thaliana</i> seeds. The seed-specific <i>DC3 PROMOTER-BINDING FACTOR2</i> (<i>DPBF2</i>) transcription factor was upregulated by <i>LEAFY COTYLEDON2</i> (<i>LEC2</i>). DPBF2 showed transcriptional activity in yeast and localized to the nucleus in Arabidopsis protoplast cells. The Arabidopsis <i>dpbf2-1</i> homozygous T-DNA mutant and transgenic lines overexpressing of <i>DPBF</i>2 using a seed-specific phaseolin promoter in wild-type (WT) Arabidopsis and in <i>dpbf2-1</i> showed similar FA composition profiles in their seeds. Their 18:2 and 20:1 FA contents were higher, but 18:1 and 18:3 contents were lower than that of WT. Transcript levels of <i>FATTY ACID DESATURASE2</i> (<i>FAD2</i>), <i>FAD3</i>, <i>LYSOPHOSPHATIDYLCHOLINE ACYLTRANSFERASE1</i> (<i>LPCAT1</i>), <i>LPCAT2</i>, <i>PHOSPHATIDYLCHOLINE DIACYLGLYCEROL CHOLINEPHOSPHOTRANSFERASE</i> (<i>PDCT</i>), and <i>FATTY ACID ELONGASE 1</i> (<i>FAE1</i>) are increased in <i>DPBF2</i>-overexpressing seeds. Besides, <i>PDCT</i> and <i>FAE1</i> were upregulated by DPBF2, LEC1-LIKE (L1L), and NUCLEAR FACTOR-YC2 (NF-YC2) transcriptional complex based on tobacco protoplast transcriptional activation assay. These results suggest that DPBF2 effectively modulates the expression of genes encoding FA desaturases, elongase, and acyl-editing enzymes for modifying the unsaturated FA composition in seeds.