Soybean LEC2 Regulates Subsets of Genes Involved in Controlling the Biosynthesis and Catabolism of Seed Storage Substances and Seed Development

Abstract

Soybean is an important oilseed crop and major dietary protein resource, yet the molecular processes and regulatory mechanisms involved in biosynthesis of seed storage substances are not fully understood. The B3 domain transcription factor (TF) LEC2 essentially regulates embryo development and seed maturation in other plants, but is not functionally characterized in soybean. Here, we characterize the function of a soybean LEC2 homolog, GmLEC2a, in regulating carbohydrate catabolism, triacylglycerol (TAG) biosynthesis, and seed development. The experimental analysis showed that GmLEC2a complemented Arabidopsis atlec2 mutant defects in seedling development and TAG accumulation. Over-expression of GmLEC2a in Arabidopsis seeds increased the TAG contents by 34% and the composition of long chain fatty acids by 4% relative to the control seeds. Transcriptome analysis showed that ectopic expression of GmLEC2a in soybean hairy roots up-regulated several sets of downstream TF genes GmLEC1, GmFUS3, GmABI3, GmDof11 and GmWRI1 that regulate the seed development and production of seed storage substances. GmLEC2a regulated the lipid transporter genes and oil body protein gene OLEOSIN (OLE1). The genes involved in carbohydrate biosynthesis and storage, such as sucrose synthesis, and catabolism of TAG, such as lipases in GmLEC2a hairy roots were down-regulated. GmLEC2a targeted metabolic genes for seed protein in soybean.

Quantitative trait loci analysis of seed oil content and composition of wild and cultivated soybean

“…In soybean, GmLEC2a, a B3 domain transcription factor, complemented the defects of the Arabidopsis atlec2 mutant in seedling development and triacylglycerol accumulation. The overexpression of GmLEC2a in Arabidopsis seeds increased triacylglycerol content by 34% and the composition of long chain fatty acids by 4% relative to the control seeds [68]. GmZIP (Glyma.10 g071700) encodes a homeobox-leucine zipper protein.…”

Global dissection of the BAHD acyltransferase gene family in soybean: Expression profiling, metabolic functions, and evolution

“…Some of the BAHD acyltransferases were also significant up-or down-regulated in GmLEC2a-overexpressing hairy roots [47]. While some genes specifically expressed in leaves (GmACT26) and roots (GmACT84, GmACT85) should not be native targets of GmLEC2a, genes that are highly expressed in seeds (GmACT15, GmACT34), pod (GmACT71, GmACT99) or open flowers (GmACT75, GmACT97) may be natural GmLEC2a targets.…”

Variation in expression of the HECT E3 ligase UPL3 modulates LEC2 levels, gene expression, seed size and crop yields in Brassica napus

“…Variation in the promoter of BnaUPL3.C03 that reduces expression and increases seed lipid content has not yet been exploited in oilseed rape breeding (Figure 7), demonstrating how lipid content and seed yields could be increased without influencing composition. The presence of a functional LEC2 ortholog in soybean 43 , and the expression of LEC2 and other B3-domain transcription factor homologs during seed lipid synthesis in sunflower 44 and oil palm 45 reveals the potential of UPL3-mediated regulation of LEC2 to increase seed lipid levels and overall yields in other major oilseed crops.…”