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FEBS Open Bio. 2013 Nov 23;4:25-32. doi: 10.1016/j.fob.2013.11.003. eCollection 2013.

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.

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1
Department of Agricultural Biotechnology, National Academy of Agricultural Science, Rural Development Administration, Suwon 441-707, Republic of Korea.

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 (20:1(Δ11)), in vegetative tissues.

KEYWORDS:

ABI3-VP1, abscisic acid-insensitive 3-viviparous 1; CaMV, cauliflower mosaic virus; Castor bean; DHA, docosahexaenoic acid; DIG, digoxigenin; Eicosenoic acid; FAE1, fatty acid elongase 1; GC, gas chromatography; LEAFY COTYLEDON2; ORF, open reading frame; RT-PCR, reverse transcription polymerase chain reaction; SSC, sodium chloride-sodium citrate; Seed maturation; TAG, triacylglycerol; TF, transcription factor; TLC, thin-layer chromatography; Transcription factor; Triacylglycerol; cDNA, complementary DNA

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