Development of the engineered "glanded plant and glandless seed" cotton.

After fiber, cottonseed is the second most important by-product of cotton production. However, high concentrations of toxic free gossypol deposited in the glands of the cottonseed greatly hamper its effective usage as food or feed. Here, we developed a cotton line with edible cottonseed by specifically silencing the endogenous expression of in the seeds, which led to a glandless phenotype with an ultra-low gossypol content in the seeds and nearly normal gossypol in other parts of the plants. This engineered cotton maintains normal resistance to insect pests, but the gossypol content in the seeds dropped by 98%, and thus, it can be consumed directly as food. The trait of a low gossypol content in the cottonseeds was stable and heritable, while the protein, oil content, and fiber yield or quality were nearly unchanged compared to the transgenic receptor W0. In addition, comparative transcriptome analysis showed that down-regulated genes in the ovules of the glandless cotton were enriched in terpenoid biosynthesis, indicating the underlying relationship between gland formation and gossypol biosynthesis. These results pave the way for the comprehensive utilization of cotton as a fiber, oil, and feed crop in the future.