Ectopic overexpression of castor bean LEAFY COTYLEDON2 (LEC2) in Arabidopsis triggers the expression of genes that encode regulators of seed maturation and oil body proteins in vegetative tissues

Abstract

The LEAFY COTYLEDON2 (LEC2) gene plays critically important regulatory roles during both early and late embryonic development. Here, we report the identification of the LEC2 gene from the castor bean plant (Ricinus communis), and characterize the effects of its overexpression on gene regulation and lipid metabolism in transgenic Arabidopsis plants. LEC2 exists as a single-copy gene in castor bean, is expressed predominantly in embryos, and encodes a protein with a conserved B3 domain, but different N- and C-terminal domains to those found in LEC2 from Arabidopsis. Ectopic overexpression of LEC2 from castor bean under the control of the cauliflower mosaic virus (CaMV) 35S promoter in Arabidopsis plants induces the accumulation of transcripts that encodes five major transcription factors (the LEAFY COTYLEDON1 (LEC1), LEAFY COTYLEDON1-LIKE (L1L), FUSCA3 (FUS3), and ABSCISIC ACID INSENSITIVE 3 (ABI3) transcripts for seed maturation, and WRINKELED1 (WRI1) transcripts for fatty acid biosynthesis), as well as OLEOSIN transcripts for the formation of oil bodies in vegetative tissues. Transgenic Arabidopsis plants that express the LEC2 gene from castor bean show a range of dose-dependent morphological phenotypes and effects on the expression of LEC2-regulated genes during seedling establishment and vegetative growth. Expression of castor bean LEC2 in Arabidopsis increased the expression of fatty acid elongase 1 (FAE1) and induced the accumulation of triacylglycerols, especially those containing the seed-specific fatty acid, eicosenoic acid (20:1Δ11), in vegetative tissues.

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

“…At 62 days after germination, the fresh masses of OIL21, OIL25 and wild‐type plants were 5.5, 5.8 and 4.6 g per plant, respectively (Figure S1c,d). The effects of the expression of senescence‐inducible LEC2 differ greatly from the severe retardation in growth and the production of embryolike structures observed in the young vegetative tissues of plants that constitutively express LEC2 (Kim et al ., ; Stone et al ., , ).…”

Lipid Droplet-Associated Proteins (LDAPs) Are Required for the Dynamic Regulation of Neutral Lipid Compartmentation in Plant Cells

“…LEC2 is a major seed-specific transcription factor that up-regulates many of the genes involved in oil biosynthesis, and ectopic expression of LEC2 in leaves elevates TAG production (Santos Mendoza et al, 2005;Andrianov et al, 2010;Petrie et al, 2010;Kim et al, 2013). The absolute amounts of oleosin transcripts induced in this system, however, are not as high as those observed in developing seeds (Feeney et al, 2013;Kim et al, 2013), and, as such, the level of TAG packaging proteins is likely to be reduced relative to TAG synthesis. Evidence in support of this premise is provided in Figure 7A, which shows that transient expression of Arabidopsis LEC2 in tobacco leaves resulted in the formation of several aberrant, supersized LDs in comparison with the wild type.…”

Transport and transcriptional regulation of oil production in plants

“…[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. ERF022 negatively regulates ethylene synthesis and positively regulates somatic embryogenesis in Arabidopsis.…”