Senescence‐inducible LEC2 enhances triacylglycerol accumulation in leaves without negatively affecting plant growth

Abstract

Summary The synthesis of fatty acids and glycerolipids in wild-type Arabidopsis leaves do not typically lead to strong triacylglycerol (TAG) accumulation. LEAFY COTYLEDON2 (LEC2) is a master regulator of seed maturation and oil accumulation in seeds. Constitutive ectopic LEC2 expression causes somatic embryogenesis and defects in seedling growth. Here, we report that senescence-inducible LEC2 expression caused a 3-fold increase in TAG levels in transgenic leaves compared with that in the leaves of wild-type plants. Plant growth was not severely affected by the accumulation the TAG in response to LEC2 expression. The levels of plastid-synthesized lipids, mono- and di-galactosyldiacylglycerol and phosphatidylglycerol, were reduced more in senescence-induced LEC2 than endoplasmic reticulum-synthesized lipids, including phosphatidylcholine, phosphatidylethanolamine, and phosphatidylinositol. Senescence-induced LEC2 upregulated the expression of many genes involved in fatty acid and TAG biosynthesis at precise times in senescent leaves, including WRINKLED1 (WRI1), which encodes a fatty acid transcription factor. The expression of glycerol-3-phosphate dehydrogenase 1 and phospholipid:diacylglycerol 2 were increased in the transgenic leaves. Five seed-type oleosin-encoding genes, expressed during oil-body formation, and the seed-specific FAE1 gene, which encodes the enzyme responsible for the synthesis of C20:1 and C22:1 fatty acids, were also expressed at higher levels in senescing transgenic leaves than in wild-type leaves. Senescence-inducible LEC2 triggers the key metabolic steps that increase TAG accumulation in vegetative tissues.

Gene coexpression network analysis of oil biosynthesis in an interspecific backcross of oil palm

“…By feeding glycerol to developing seeds in planta (Vigeolas and Geigenberger, ), or by overexpressing a yeast cytosolic GPDH using a seed‐specific promoter (Vigeolas et al ., ), it is possible to obtain a significantly increased seed oil content in Brassica , suggesting that the supply of G3P is rate‐limiting for TAG synthesis. In Arabidopsis, senescence‐induced LEC2 expression caused a three‐fold increase in TAG levels in leaves (Kim et al ., ). LEAFY COTYLEDON2 (LEC2) is a master regulator of seed maturation and oil accumulation in Brassicaceae seeds (Baud et al ., ; Santos Mendoza et al ., ).…”

Expression of Camelina WRINKLED1 Isoforms Rescue the Seed Phenotype of the Arabidopsis wri1 Mutant and Increase the Triacylglycerol Content in Tobacco Leaves

“…WRI1 is a regulator of lipid accumulation downstream of the above four master regulators (Roscoe et al, 2015). Recently, researchers have attempted to produce vegetable oil (TAG or fatty acids) in leaves with the overexpression of a key regulator WRI1 for fatty acid synthesis as well as senescence-inducible or xylem-specific expression of LEC2 , which is a transcription factor involved in the early stages of seed development (Kim et al, 2015). In most cases, since Arabidopsis WRI1 gene has not shown any negative effect on plant growth, it has been used mainly for the production of TAG in the vegetative tissues.…”

Transport and transcriptional regulation of oil production in plants

“…[61] Since the constitutive expression of LEC2 usually causes somatic embryogenesis and defects in seedling growth, a senescence-inducible LEC2 was shown to increase TAG production by three-folds in transgenic leaves, at the cost of reduced biosynthesis of plastid-synthesized lipids, including MGDG, DGDG, and PG. [70] LEC2 inducible expression changes FA composition of vegetative tissues by up-regulating LEC1, ABI3, FUS3, LEC2, and WRI1 that may further induce accumulation of FA elongase 1 (FAE1) and oleosin transcripts. [71] An ethylene response factor 022 (ERF022) interacts with LEC2 and regulates somatic embryogenesis.…”