Gossypol and related compounds are produced and accumulate in the aboveground parts of the cotton plant, independent of roots as the source

Authors: PANDEYA, DEVENDRA - Texas A&M University; CAMPBELL, LEANNE - Texas A&M University; Puckhaber, Lorraine; Suh, Charles; RATHORE, KEERTI - Texas A&M University

Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/9/2022
Publication Date: 12/20/2022
Citation: Pandeya, D., Campbell, L.M., Puckhaber, L.S., Suh, C.P., Rathore, K.S. 2022. Gossypol and related compounds are produced and accumulate in the aboveground parts of the cotton plant, independent of roots as the source. Plants. 257. Article 21. https://doi.org/10.1007/s00425-022-04049-0.
DOI: https://doi.org/10.1007/s00425-022-04049-0

Interpretive Summary: Terpenoid aldehydes, such as gossypol, are a group of compounds produced by cotton plants that help protect the plants from insects and pathogens. These defensive compounds are present in most parts of the plant, including cotton seed. Gossypol is of particular interest because this compound is toxic to mammals. Consequently, there has been substantial breeding efforts to produce cotton plants with normal levels of gossypol in the roots and leaves of plants but with no or ultra low levels of gossypol in cotton seed so that the seeds can be used for animal feed. However, it has been speculated that gossypol and related compounds produced in the roots of plants can be transported to replenish the defensive contents in above ground parts of the plant. Based on grafting and genetic modification experiments, our work revealed that gossypol and related compounds produced in the roots of cotton plants are not transported to other parts of the plant but remain and accumulate locally within the respective plant structures. Thus, cotton seeds from plants that have been bred or genetically modified to produce seed with no or ultra low levels of gossypol should remain safe for animal feed.

Technical Abstract: Gossypol and related terpenoids, derived from the same biosynthetic pathway, are present in the numerous lysigenous glands in the above ground parts of a cotton plant. Roots, with sparse presence of such glands, do produce significant amount of gossypol and a different set of terpenoids. These compounds serve a defensive function against various pests and pathogens. This investigation was undertaken to examine whether gossypol produced in the roots can replenish the gossypol content of the cottonseed-glands that are largely devoid of this terpenoid in a genetically engineered event. Graft unions between a scion derived from the RNAi-based, Ultra-low Gossypol Cottonseed (ULGCS) event, TAM66274, and a rootstock derived from wild-type parental genotype, Coker 312 (Coker) were compared with various other grafts that served as controls. The results showed that the seeds developing within the scion of test grafts (ULGCS/Coker) continued to maintain the ultra-low gossypol levels found in the TAM66274 seeds. Moreover, molecular analyses confirmed that while the key gene involved in gland development showed normal activity in the developing embryos in the scion, two genes encoding the enzymes involved in gossypol biosynthesis were suppressed. Thus, the gene expression data confirmed the results obtained from biochemical measurements, and collectively demonstrated that roots are not a source of gossypol for the above-ground parts of the cotton plant. These findings, combined with the results from previous investigations, support the assertion that gossypol and related terpenoids are produced in a highly localized manner in various organs of the cotton plant and are retained therein.