Submitted to: Proceedings of the National Academy of Sciences (PNAS)
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/4/2006
Publication Date: 11/20/2006
Citation: Sunilkumar, G., Campbell, L.M., Puckhaber, L.S., Stipanovic, R.D., Rathore, K. 2006. Engineering cottonseed for use in human nutrition by tissue-specific reduction of toxic gossypol. Proceedings of the National Academy of Sciences. 103:18054-18059.
Interpretive Summary: Cottonseed could provide the protein requirements for half a billion people per year. However, cottonseed contains a naturally occurring toxic compound called gossypol. Thus, it is not possible to feed cottonseed to non-ruminant animals including people. Total removal of gossypol from the plant is not a viable method to make cottonseed suitable for non-ruminant consumption because gossypol and related compounds protect the plant from insects and diseases. Using genetic engineering, we were able to achieve a 100-fold reduction in gossypol content in seed as compared to that found in normal cottonseed; notably, the concentration of gossypol and related compounds in the foliage was not reduced. Thus, it may be possible to feed cottonseed derived from these plants directly to poultry, pigs, and fish. Poultry and fish are more than twice as efficient at converting the food they eat into body weight. Thus, this technology could significantly increase cottonseed utilization in the U. S. and reduce hunger in developing countries where over 60% of the world's cotton is currently produced.
Technical Abstract: Global cottonseed production can potentially provide the protein requirements for half a billion people per year, however, it is woefully underutilized because of the presence of toxic gossypol within seed-glands. Therefore, elimination of gossypol from cottonseed has been a long-standing goal of geneticists. Attempts were made to meet this objective by developing so-called glandless cotton in the 1950s via conventional breeding techniques; however, the glandless varieties were commercially unviable because of the increased susceptibility of the plant to insect pests due to the systemic absence of glands that contain gossypol and other protective terpenoids. Thus, the promise of cottonseed in contributing to the food requirements of the burgeoning world population remained unfulfilled. We examined whether RNA interference (RNAi) can be employed to disrupt gossypol production in a tissue (seed)-specific manner. In this study, we demonstrate that targeted engineering of the gossypol biosynthetic pathway by interfering with the expression of the delta-cadinene synthase gene during seed development resulted in a significant reduction in cottonseed-gossypol levels. Results from molecular analyses on developing, transgenic embryos were consistent with the observed phenotype in the mature seeds. Importantly, the levels of gossypol and related terpenoids in the foliage and floral parts were not diminished and thus remain available for plant defence against insects and diseases. These results illustrate that a single-step, targeted genetic modification applied to an underutilized agricultural byproduct provides a mechanism to open up a new source of nutrition for hundreds of millions of people. Similar approaches can be applied to eliminate toxins from other potential food sources to improve global food security.