Cotton roots are the major source of gossypol biosynthesis and accumulation

Authors: ZHAO, TIANLUN - Zhejiang University; XIE, QIANWEN - Zhejiang University; LI, CONG - Zhejiang University; LI, CHENG - Zhejiang University; MEI, LEI - Zhejiang University; Yu, John; CHEN, JINHONG - Zhejiang University; ZHU, SHUIJIN - Zhejiang University

Submitted to: BMC Plant Biology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/17/2020
Publication Date: 2/27/2020
Citation: Zhao, T., Xie, Q., Li, C., Li, C., Mei, L., Yu, J., Chen, J., Zhu, S. 2020. Cotton roots are the major source of gossypol biosynthesis and accumulation. Biomed Central (BMC) Plant Biology. 20:88. https://doi.org/10.1186/s12870-020-2294-9.
DOI: https://doi.org/10.1186/s12870-020-2294-9

Interpretive Summary: The cotton plant not only produces natural fiber for the textile industry, but also produces cottonseeds that contain high-quality protein and oil. However, the commercial utilization of cottonseeds is greatly hindered by a toxic metabolite called gossypol. At present, little is known about the metabolism of the gossypol compound in cotton. This study demonstrates that gossypol is primarily synthesized and accumulated in the root systems of both glanded and glandless cotton plants. Gossypol synthesis is not directly related to the production of pigment glands, but the presence of pigment glands is essential for gossypol accumulation. The new knowledge from this study sheds light into the complexity of gossypol metabolism, and it will help cotton breeders enhance the commercial value of cottonseeds in addition to the fiber produced.

Technical Abstract: Gossypol is a specific secondary metabolite in Gossypium species. It not only plays a critical role in the development and self-protection of cotton plants, but it also can be used as an important anti-cancer and male contraceptive compound. However, because of the toxicity of gossypol for human beings and monogastric animals, the utilization of cottonseeds has been limited. To date, little is known about gossypol metabolism in cotton plants. In this study, we found that the primary source of gossypol was the cotyledons at the seed germination stage, and later in development, gossypol mainly originated from the root system. Grafting with different combinations of glanded and glandless cottons as well as sunflower rootstocks and cotton scions revealed that gossypol was mainly synthesized in the root systems of cotton plants, and both glanded and glandless cotton roots were able to synthesize gossypol. The pigment glands, the main storage location of gossypol, had indirect effects on gossypol biosynthesis. In vitro culture of rooted and rootless seedlings confirmed the strong role of the root system in gossypol biosynthesis and the relatively weak gossypol biosynthesis ability in other organs of the seedling. Expression profiling of the key genes involved in the gossypol biosynthetic pathway also supported the root as the major organ of gossypol biosynthesis. Our study provides evidence that the cotton root system is the major source of gossypol in both glanded and glandless cottons while other organs have a relatively weak ability to synthesize gossypol. Gossypol biosynthesis is not directly related to the production of pigment glands, but the presence of pigment glands is essential for gossypol accumulation. These findings not only clarify the complex regulation network of gossypol metabolism, but also will provide another breeding objective with the potential to enhance the commercial value of the cotton crop.