Increasing seed oil yield is one of the most important goals for oilseed crop improvement. This project aims to enhancing seed oil content and extractability of oilseed crops by metabolic engineering of phenylpropanoid metabolism. We will manipulate flavonoid and lignin biosynthesis to enhance seed oil accumulation and test the hypothesis that modification of lignin in seed coat will facilitate the extraction of oil from seeds. Two emerging promising biofuel oilseed crops, camelina and pennycress, will be engineered by the CRISPR-Cas9 and RNAi technology.
In recent years, camelina (Camelina sativa) and pennycress (Thlaspi arvense) have been emerging as promising temperate oilseed crops for biodiesel and jet fuel production. Camelina and pennycress produce seeds with high oil content and suitable fatty acid profile for “drop-in” biofuel applications. Both camelina and pennycress have agronomic characteristics desirable for biofuel crops. They require low agricultural input such as water, pesticides, and fertilizer, and perform well on marginal lands. And these two oilseed crops are compatible with existing farm infrastructure and practices. Moreover, pennycress and winter camelina are cold tolerant and have a short life cycle, which allow them to be integrated into the prominent corn-soybean cropping system in the US Corn Belt. In addition to increasing the land use efficiency and productivity per unit area, camelina and pennycress also serve as winter cover crops that provide many environmental benefits, including limiting soil erosion, reducing nutrient loss, improving water quality, repressing weed growth, and enhancing pollinator abundance.
Improvement of pennycress and camelina will contribute to sustainable biofuel production without competition with food supplies. Oilseeds with high extractability and oil content will enable local seed pressing practice on small and medium-sized farms, fostering rural economic growth. Successful completion of this project will also provide new tools and strategies that can be used to increase the oil production of other oilseed crops.
Pennycress and Camelina
The phenylpropanoid pathway gives rise to a wide variety of specialized metabolites that have diverse functions in plants. Lignin, a major product of this pathway, is deposited in secondary cell wall increasing its mechanical strength and hydrophobicity. Because of this phenolic polymer’s negative impact on the utilization of cellulosic biomass for animal feed, paper pulp, and biofuels, there has been a great deal of interest in manipulating lignin biosynthesis to improve the extractability of cell wall polysaccharides.
Lignin modification induced dwarfism (LMID) is a major hurdle for developing biofuel feedstocks with improved cell wall degradability through genetic modification of lignin pathway. It is widely observed that disruption of lignin biosynthesis often results in plant growth inhibition and thereby reduced biomass.
We have carried out a suppressor screen on the Arabidopsis ref8 mutant and isolated more than twenty suppressor lines which retained the defect in lignin biosynthesis of the original mutant but showed an alleviated growth phenotype. Mapping the suppressor genes, named as GROWTH INHIBITION RELIEVED (GIR), from this mutant collection allowed us to discover key genetic components of LMID. These discoveries provide us a unique opportunity to dissect the transcriptional regulatory framework of LMID. In this project, we are using a systematic multiple omics approach to gain mechanistic insight into the transcriptional regulation of LMID.
This project focuses on plant secondary metabolism. Plants can produce a large array of diverse specialized metabolites, many of which are known to have beneficial effects on human health. Understanding how these compounds are made and accumulated in plants will enable us to produce crops, vegetables and fruits for enhanced health-promoting properties.
We are working to identify novel plant secondary metabolites and to discover the genes and pathways for the biosynthesis of these compounds using natural accessions of Arabidopsis thaliana. This research will not only advance our understanding of plant secondary metabolism in the model plant Arabidopsis, but will also lead to the development of an integrated metabolomics, genetics and genomics discovery platform that can be applied to gain insight in the biochemical pathways and gene networks involved in the accumulation of bioactive compounds in crops, vegetables and fruits.