The increasing need for healthy edible oil has driven us to identify α-linolenic acid (ALA)-rich species and identify key biochemical steps in ALA synthesis. Seeds of tree peony species are rich in unsaturated fatty acid content with > 40% ALA in the total fatty acid. However, fatty acid content and composition is variable among the tree peony germplasm. To this extent, a comparative study was carried out to identify the key genes responsible for differential oil accumulation among nine wild tree peony species. Subsequent to analyzing fatty acid content and composition of the seeds from nine tree peony species, a high- (P. rockii) and low-oil (P. lutea) accumulating species were selected for transcriptome analysis. Gene expression analysis revealed upregulation of select genes involved in plastidial fatty acid synthesis, and acyl editing, desaturation and triacylglycerol assembly in the endoplasmic reticulum in seeds of P. rockii relative to P. lutea. Also, in association with ALA content in seeds, transcript levels for fatty acid desaturases (SAD, FAD2 and FAD3), which encode for enzymes necessary for polyunsaturated fatty acid synthesis were higher in P. rockii compared to P. lutea. Additionally, we showed that the overexpression of PrFAD2 and PrFAD3 in Arabidopsis increased linoleic and α-linolenic acid content, respectively and modulated their final ratio in the seed oil. In conclusion, we identified the key steps that contribute to efficient ALA synthesis and validated the necessary desaturases in P. rockii that are responsible for not only increasing oil content but also modulating 18:2/18:3 ratio in seeds. Together, these results will aid to improve essential fatty acid content in seeds of tree peonies and other crops of agronomic interest.
Johnson City, TN
Xie, Lihang H.; Zhang, Qingyu; Kilaru, Aruna; and Zhang, Yanlong. 2019. Tree Peony Species as an Efficient Source for α-Linolenic Acid Production. Oral Presentation. Phytochemical Society of North America Annual Meeting, Johnson City, TN. https://www.psna-online.org/PSNA%202019%20FINAL%20PROGRAM.pdf