An overview of pigment gland morphogenesis and its regulatory mechanism

Cotton has enormous economic potential, providing high-quality protein, oil, and fibre. But the comprehensive utilization of cottonseed is limited by the presence of pigment gland and its inclusion. Pigment gland is a common characteristic of Gossypium genus and its relatives, appearing as visible dark opaque dots in most tissues and organs of cotton plants. Secondary metabolites, such as gossypol, synthesized and stored in the cavities of pigment glands act as natural phytoalexins, but are toxic to humans and other monogastric animals. However, only a few cotton genes have been identified as being associated with pigment gland morphogenesis to date, and the developmental processes and regulatory mechanism involved in pigment gland formation remain largely unclear. Here, the research progress on the process of pigment gland morphogenesis and the genetic basis of cotton pigment glands is reviewed, for providing a theoretical basis for cultivating cotton with the ideal pigment gland trait.