WRI1‐1, ABI5, NF‐YA3 and NF‐YC2 increase oil biosynthesis in coordination with hormonal signaling during fruit development in oil palm

Abstract

The oil biosynthesis pathway must be tightly controlled to maximize oil yield. Oil palm accumulates exceptionally high oil content in its mesocarp, suggesting the existence of a unique fruit-specific fatty acid metabolism transcriptional network. We report the complex fruit-specific network of transcription factors responsible for modulation of oil biosynthesis genes in oil palm mesocarp. Transcriptional activation of EgWRI1-1 encoding a key master regulator that activates expression of oil biosynthesis genes, is activated by three ABA-responsive transcription factors, EgNF-YA3, EgNF-YC2 and EgABI5. Overexpression of EgWRI1-1 and its activators in Arabidopsis accelerated flowering, increased seed size and oil content, and altered expression levels of oil biosynthesis genes. Protein-protein interaction experiments demonstrated that EgNF-YA3 interacts directly with EgWRI1-1, forming a transcription complex with EgNF-YC2 and EgABI5 to modulate transcription of oil biosynthesis pathway genes. Furthermore, EgABI5 acts downstream of EgWRKY40, a repressor that interacts with EgWRKY2 to inhibit the transcription of oil biosynthesis genes. We showed that expression of these activators and repressors in oil biosynthesis can be induced by phytohormones coordinating fruit development in oil palm. We propose a model highlighting a hormone signaling network coordinating fruit development and fatty acid biosynthesis.

Review: Omics and Strategic Yield Improvement in Oil Crops

“…In addition to WRINKLED1, they identified two novel transcription factors, termed NF-YB-1 and ZFP-1, observed to activate fatty acid synthesis genes. The understanding of this transcription factor network in oil palm mesocarp was further extended by Yeap et al [96] in which EgWRI1-1 was found to be activated by three ABAresponsive transcription factors; EgNF-YA3, EgNF-YC2, and EgABI5. Two repressors of this network were also identified, EgWRKY40 and EgWRKY2, and overall this study enabled a hormone signaling network model to be postulated that coordinates fruit development and fatty acid biosynthesis.…”

“…Oleosins are not highly expressed in non-seed oil-accumulating tissues such as the mesocarp of olive, oil palm, and avocado [94]. Transcriptome studies on the oil-rich mesocarp of olive, oil palm, and avocado have also revealed important differences in the transcriptional control of lipid biosynthesis in the mesocarp to that of oil-rich seeds [49,90,91,[95][96][97]. In oil-rich seeds, many of the key regulators of embryogenic development and seed maturation, including abscisic acid-insensitive3 gene and LEAFY COTYLEDON group genes (e.g., LEC1, LEC1like, LEC2, and FUSCA3) control lipid biosynthesis through the downstream transcription factor WRINKLED1 [34,49,[98][99][100][101].…”

Molecular Basis of Plant Oil Biosynthesis: Insights Gained From Studying the WRINKLED1 Transcription Factor

“…In oil palm mesocarp, where most palm oil is derived from and EgWRI1 displays high expression, the inability to detect expression of key regulator genes, such as EgLEC1, EgLEC2, and EgFUS3, suggests that expression of EgWRI1 involves additional fruit-specific upstream regulators (Bourgis et al, 2011). EgNF-YA3, EgNF-YC2, and EgABI5 have been recently found to be capable of binding to the promoter region and activate the expression of EgWRI1 (Yeap et al, 2017).…”

Expression of the Arabidopsis WRINKLED 1 transcription factor leads to higher accumulation of palmitate in soybean seed

“…Further studies showed that AtWRI1 also plays a role in processes such as lipid assembly, storage, flowering time, seed development, embryo maturation, plant hormone regulation, and photosynthesis (Cernac et al, 2006;Kong et al, 2017;Li et al, 2015;Maeo et al, 2009;Wu et al, 2014). A number of other communications have also revealed orthologs of AtWRI1 being involved in plant oil biosynthesis (Adhikari et al, 2016;Bhattacharya et al, 2016;Chen et al, 2017;Ivarson et al, 2016;Kang et al, 2017;Kim et al, 2016;Liu et al, 2010;Ma et al, 2013;Pouvreau et al, 2011;Shen et al, 2010;Vanhercke et al, 2013;Wu et al, 2014;Yeap et al, 2017). For example, expression of the Brassica napus WRI1(BnWRI1) in Arabidopsis promoted between 10% and 40% increased seed oil content and led to larger seed and size mass (Liu et al, 2010).…”