Production of tocotrienols in seeds of cotton (Gossypium hirsutum L.) enhances oxidative stability and offers nutraceutical potential

Authors: SALIMATH, SHANMUKH - University Of North Texas; ROMSDAHL, TREVOR - University Of North Texas; KONDA, ANJI - University Of Nebraska; ZHANG, WEI - Huazhong Agricultural University; CAHOON, EDGAR - University Of Nebraska; Dowd, Michael; WEDEGAERTNER, THOMAS - Cotton, Inc; HAKE, KATER - Cotton, Inc; CHAPMAN, KENT - University Of North Texas

Submitted to: Plant Biotechnology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/15/2021
Publication Date: 2/17/2021
Citation: Salimath, S.S., Romsdahl, T.B., Konda, A.R., Zhang, W., Cahoon, E.B., Dowd, M.K., Wedegaertner, T.C., Hake, K.D., Chapman, K.D. 2021. Production of tocotrienols in seeds of cotton (Gossypium hirsutum L.) enhances oxidative stability and offers nutraceutical potential. Plant Biotechnology Journal. 19:1268-1282. https://doi.org/10.1111/pbi.13557.
DOI: https://doi.org/10.1111/pbi.13557

Interpretive Summary: Vitamin E consists of a a group of compounds that include tocopherols and tocotrienols. In plants, these compounds exhibit strong antioxidant activity that help rotect the plant from oxidative stress. Cotton, like many dicot plants, only has the tocopherol compounds. As a result, cottonseed oil lacks the tocotrienols, unlike many other vegetable oils, e.g., corn, rice bran, and palm kernel oils. To see if cotton plants could produce tocotrienol compounds, a tocotrienol synthesis enzyme from barley was engineered into the plant. The modified plants were found to produce the three of the four forms of tocotrienol, and the vitamin E levels in these plants were increased up to 3-fold compared with the unmodified plants. The seeds from these plants had increased antioxidant activity, and the extracted oils were found to have improved oxidative stability. The study could result in cottonseed oils with longer shelf life and improved stability when used for deep fat frying.

Technical Abstract: Upland cotton (Gossypium hirsutum L.) is an economically important multi-purpose crop cultivated globally for its fiber, seed oil, and seed protein. Cottonseed oil also is a naturally rich source of vitamin E with a- and '-tocopherols comprising nearly all of the vitamin E in cottonseed oil. Cottonseeds, similar to other dicot oilseeds, completely lack tocotrienols (the unsaturated versions of the tocopherols). Here, we generated transgenic cotton plants carrying the Hordeum vulgare (Hv; barley) homogentisate geranylgeranyl transferase coding sequence under the control of the Brassica napus (rape) seed-specific promoter, napin. Transgenic cottonseeds showed a 2- to 3-fold increase in the accumulation of total vitamin E (tocopherols + tocotrienols), which included more than 60% '--tocotrienol. Matrix assisted laser desorption ionization-mass spectrometry imaging showed that '-tocotrienol was localized throughout the transgenic embryos. In contrast, the native tocopherols were distributed unequally in both transgenic and non-transgenic embryos––a-tocopherol being restricted mostly to the cotyledon tissues and '-tocopherol being more localized in the embryonic axis tissues. Production of tocotrienols in cotton embryos had no negative impact on plant performance including the yields of important seed constituents, i.e., fiber, oil and protein. Advanced generations of two transgenic events were field grown, and extracts of transgenic seeds showed increased antioxidant activity relative to non-transgenic seeds. Furthermore, solvent-extracted, refined cottonseed oil from the two transgenic events showed 30% improvement in oxidative stability relative to the non-transgenic cottonseed oil. Taken together, these materials may provide new opportunities for cottonseed products with enhanced vitamin E profile.