Tung tree (Vernicia fordii, Hemsl.) genome and transcriptome sequencing reveals co-ordinate up-regulation of fatty acid beta-oxidation and triacylglycerol biosynthesis pathways during eleostearic acid accumulation in seeds

Authors: CUI, PENG - Chinese Academy Of Agricultural Sciences; LIN, QIANG - Chinese Academy Of Sciences; FANG, DONGMING - Chinese Academy Of Agricultural Sciences; ZHANG, LINGLING - Chinese Academy Of Sciences; LI, RONGJUN - Chinese Academy Of Sciences; CHENG, JUNYONG - Hubei Academy Of Agricultural Sciences; GAO, FEI - Chinese Academy Of Agricultural Sciences; Shockey, Jay; HU, SONGNIAN - Chinese Academy Of Sciences; LU, SHIYOU - Chinese Academy Of Sciences

Submitted to: Plant and Cell Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/10/2018
Publication Date: 8/21/2018
Citation: Cui, P., Lin, Q., Fang, D., Zhang, L., Li, R., Cheng, J., Gao, F., Shockey, J., Hu, S., Lu, S. 2018. Tung tree (Vernicia fordii, Hemsl.) genome and transcriptome sequencing reveals co-ordinate up-regulation of fatty acid beta-oxidation and triacylglycerol biosynthesis pathways during eleostearic acid accumulation in seeds. Plant And Cell Physiology. 59:1990-2003. https://doi.org/10.1093/pcp/pcy117.
DOI: https://doi.org/10.1093/pcp/pcy117

Interpretive Summary: For decades, tung tree orchards were a prominent agricultural feature across the Gulf Southern states in the U.S. The tung oil produced from the seeds of these trees is a value-added drying oil, and had also been used in the production of various chemical products such as inks, dyes, coatings, resins, and biodiesel. Several hurricanes, starting with Betsy in 1969 through Katrina and Rita in 2005, decimated the tung oil orchards. ARS researchers in New Orleans, Louisiana have sought to engineer the production of tung oil into other oilseed crops that are less prone to environmental damage, thus potentially producing a stable domestic supply of tung oil. Progress in this regard was hindered for years by a lack of information about the genes and enzymes that are required to produce tung seed oil. Working with collaborators in China, the DNA sequence of the genome of the tung tree was determined. This resource will be invaluable as a tool to study the genetics of tung oil production.

Technical Abstract: The tung tree (Vernicia fordii) is one of only a few plant species that produces high oil-yielding seeds rich in a-eleostearic acid (a-ESA, 18:3'9cis,11trans,13trans), a conjugated trienoic fatty acid with valuable industrial and medical properties. Previous attempts have been made to engineer tung oil biosynthesis in transgenic oilseed crops, but these efforts have met with limited success. Here we present a high-quality genome assembly and developing seed transcriptomic data set for this species. Whole-genome shotgun sequencing generated 176 Gb of genome sequence data used to create a final assembled sequence 1,176,320 kb in size, with a scaffold N50 size of >474 kb, and containing ~47,000 protein-coding genes. Genomic and transcriptomic data revealed full-length candidate genes for most of the known and suspected reactions that necessary for fatty acid desaturation/conjugation, acyl editing, and triacylglycerol biosynthesis. Seed transcriptomic analyses also revealed features unique to tung tree, including unusual transcriptional profiles of fatty acid biosynthetic genes, and coordinated (and seemingly paradoxical) simultaneous upregulation of both fatty acid beta-oxidation and triacylglycerol biosynthesis in mid-development seeds. The precise temporal control of the expression patterns for these two pathways may account for a-ESA enrichment in tung seeds, while controlling the levels of potentially toxic byproducts. Deeper understanding of these processes may open doors to the design of engineered oilseeds containing high levels of a-ESA.