TOWARD CONTROL STRATEGIES OF EMERGING PATHOGENS AND NEMATODES OF COTTON
Location: Cotton Pathology Research
Title: Ultra-low gossypol cottonseed: generational stability of the seed-specific, RNAi-mediated phenotype and resumption of terpenoid activity/profile following seed germination
Submitted to: Plant Biotechnology Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 11, 2011
Publication Date: February 8, 2012
Citation: Rathore, K., Sundaram, S., Sunilkumar, G., Campbell, L., Puckhaber, L.S., Marcel, S., Palle, S., Stipanovic, R.D., Wedegaertner, T. 2012. Ultra-low gossypol cottonseed: Generational stability of the seed-specific, RNAi-mediated phenotype and resumption of terpenoid activity/profile following seed germination. Plant Biotechnology Journal. pp. 1-10.
Interpretive Summary: Cottonseed, which contains 22.5% protein, remains an under-utilized and under-valued food or feed resource due to the presence of a toxic compound called gossypol. However, using gene technology we have developed cotton plants that produce cottonseed that contain ultra low levels of gossypol. In addition to producing gossypol, cotton plants also produce chemicals that are similar to gossypol in the other parts of the plant. These chemicals help protect the plant from attack by insects and pathogens. The production of the other chemicals in the ultra low level gossypol plants have not been studied during early plant development. We now show that the production of these other protective chemicals in the ultra low gossypol plants is not different than that observed in plants that do not exhibit the ultra low gossypol seed trait, and they are not unusually susceptible to pathogens.
Cottonseed, containing 22.5% protein, remains an under-utilized and under-valued resource due to the presence of toxic gossypol. RNAi-knockdown of Beta-cadinene synthase gene(s) was used to engineer plants that produced ultra-low gossypol cottonseeds (ULGCS). In the original study, we observed that cotton plants that were a month or older maintain normal complement of gossypol and related terpenoids in the roots, foliage, floral organs, and young bolls. However, the terpenoid profile of the RNAi lines during the early stages of germination, under normal conditions and in response to pathogen exposure, had not been examined. Results obtained in this study show that during the early stages of seed germination/seedling growth, in both non-transgenic and RNAi lines, the tissues derived directly from bulk of the seed kernel (cotyledon and hypocotyl) synthesize little, if any new terpenoids. However, the growing root tissue and the emerging true leaves of RNAi seedlings showed normal, wild-type terpenoid levels. Biochemical and molecular analyses showed that pathogen-challenged parts of RNAi seedlings are capable of launching a terpenoid-based defense response. Nine different RNAi lines were monitored for five generations. The results show that, unlike the unstable nature of antisense-mediated low seed-gossypol phenotype, the RNAi-mediated ULGCS trait exhibited multi-generational stability.