Gossypol biosynthesis in cotton revealed through organ culture, plant grafting and gene expression profiling

Abstract Gossypol plays an important role in defense mechanism of Gossypium species and the presence of gossypol also limits the utilization of cottonseeds. However, little is known about the metabolism of gossypol in cotton plant. Here, Detection on the dynamic tendency of gossypol content illustrated that at the germination stage, the main source of gossypol was cotyledon, and at the later stages, gossypol mainly came from root system. Plant grafting between cottons and sunflower proved that gossypol was mainly synthesized in the root systems of cotton plants and both of the glanded and glandless cottons had the ability of gossypol biosynthesis. Besides, the pigment glands expression was uncoupled with gossypol biosynthesis. Root tip and rootless seedling organ culture in vitro further revealed other parts of the seedlings also got the ability to synthesize gossypol except root system. Moreover, root system produced the racemic gossypol and plant synthesized the optically active gossypol. The expression profiling of key genes in the gossypol biosynthetic pathway suggested that downstream key genes had relatively high expression levels in root systems which confirmed that gossypol was mainly synthesized in the root systems. Taken together, our results helped to clarify the complex mechanism of gossypol metabolism.