Current progress on improving hydroxy fatty acid production in lesquerella (Physaria fendleri) through metabolic engineering

Authors: Chen, Grace

Submitted to: American Chemical Society
Publication Type: Abstract Only
Publication Acceptance Date: 5/15/2020
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: The conventional source of hydroxy fatty acid (HFA) is castor (Ricinus communis) oil which contains 90% ricinoleic acid (18:1OH) of total fatty acids in seed. HFA and its derivatives are used as raw materials for numerous industrial products, such as lubricants, plasticizers and surfactants. The production of castor oil, however, is hampered by the presence of the toxin ricin and hyperallergic 2S albumins. Lesquerella does not have such biologically toxic compounds and also contains a major HFA, lesquerolic acid (20:1OH), at 55-60% of seed oil. Therefore, lesquerella is being developed as a new industrial oilseed crop in the US. Biotechnology methods are effective for improving lesquerella through Agrobacteria-mediated genetic transformation. Lesquerella seed developmental studies show changes of morphology and physiology, as well as temporal details of fatty acid composition and gene expression patterns. Synthesis of 20:1OH is through elongation of 18:1OH, and the step is regulated largely by gene transcription of an elongase, PfKCS3. By silencing PfKCS3, transgenic lesquerella increased 18:1OH content from ~3% to ~27%. It is known that most of the HFAs in lesquerella are located only at sn-1 and sn-3 positions of triacylglycerols (TAG). To improve HFA levels in lesquerella seeds, castor lysophosphatidic acid acyltransferase gene 2 (RcLPAT2) have been introduced into lesquerella. The resulted transgenic lesquerella seeds increase 18:1OH content at the sn-2 position of TAG from 2% to 17%, and consequently, oil accumulates more TAGs with all three sn positions occupied by HFA. Regiobiochemical analysis reveals the role of castor LPAT2 in the accumulation of hydroxy fatty acids in transgenic lesquerella seeds by exclusively acylating 18:1OH at the sn-2 position of tri-HFA-TAG in lesquerella seed oil. The results enhance our understanding of plant lipid metabolism and provide invaluable guidance for future research, not only for enhancing HFA content in lesquerella, but also for HFA production in other oilseeds.