Submitted to: Plant Biology
Publication Type: Abstract Only
Publication Acceptance Date: 3/6/2006
Publication Date: 6/30/2006
Citation: Rathore, K.S., Sunilkumar, G., Campbell, L.M., Puckhaber, L.S., Stipanovic, R.D. 2006. Selective inhibition of delta-cadinene synthase activity overcomes the limitations of plant breeding in reducing toxic gossypol from cottonseed [abstract]. Plant Biology. Paper No. P47002.
Technical Abstract: The presence of gossypol, a cardio- and hepatotoxic terpenoid in the glands of cottonseed limits the use of this agricultural resource representing nearly 10 million metric tons of protein per year. Attempts were made to eliminate gossypol from cottonseed 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. We examined whether RNA interference can be employed to disrupt a key step in the biosynthesis of gossypol in a seed-specific manner in cotton (Gossypium hirsutum L.). We demonstrate that by interfering with the expression of the delta-cadinene synthase gene during seed development, it is possible to significantly decrease the activity of the corresponding enzyme resulting in virtual elimination of gossypol from cottonseed. Compared to an average gossypol value of 10 microgram/mg in wild-type seeds, individual transgenic seeds showed values as low as 0.1 microgram/mg, a 100-fold reduction. Results from molecular analyses on the developing, transgenic embryos were consistent with the reduced delta-cadinene synthase activity and the low-gossypol phenotype in the mature seeds. Importantly, the levels of gossypol and related terpenoids that are derived from the same pathway were not diminished in the foliage and floral parts of these plants and thus remain available for plant defense against insects and diseases. These results illustrate that it is possible to modify a biosynthetic pathway selectively to overcome the limitations of plant breeding in achieving targeted removal of a toxic secondary metabolite.