Tracking the flow of carbon toward oil synthesis in an emerging crop lesquerella (Physaria fendleri)

Abstract

Lesquerella (Physaria fendleri) is a Brassicaceae that produces hydroxy fatty acids (HFAs) in its embryos; a type of oil that is very valuable and widely used in the industry of cosmetics, coatings, greases, plastics, paints, and biofuel, among others. The current source of HFAs is ricinoleic acid which comes from castor (Ricinus communis). Unfortunately, its large‐scale production has been banned from the United States because castor contains the highly toxic compound ricin. On the other hand, free of toxins and rich in HFAs, lesquerella is an attractive alternative to imported castor oil, and is hence in the verge of commercialization. Moreover, lesquerella has tremendous potentials for oil production, has a short maturity time and is not used for food compared to other oilseed crops. However, to become economically viable, lesquerella first must be engineered to synthesize more HFAs. A lack of knowledge of the metabolic pathways underlying oil synthesis in lesquerella embryos presents a major constraint.In plants, fatty acid synthesis occurs in plastids and requires carbon in the form of acetyl‐CoA units as well as reducing power and energy. In order to assess the contribution of the pathways involved in fatty acid biosynthesis in terms of carbon, reductant and energy, a 13C‐Metabolic Flux Analysis, aka fluxomics, is being conducted. 13C‐labeling of developing embryos is required for this purpose. Our most recent work done towards meeting this goal is: (i) obtaining culture conditions for growing lesquerella embryos in vivo so that their biomass composition matches that of embryos grown in planta, (ii) determining the efficiency at which the embryos convert carbon into biomass (iii) tracking the flow of carbon towards oil synthesis using labeled substrates (13C‐glucose or 13C‐glutamine). The combination of the data from the above studies will permit to construct a flux map that will unravel possible “road blocks” in fatty acid production. Future work will consist in targeting these limiting steps through metabolic engineering to increase total fatty acids in lesquerella embryos.Support or Funding InformationAgriculture and Food Research Initiative competitive grant # 2016‐67013‐24605 of the USDA National Institute of Food and Agriculture.