Genetics of sex determination in flowering plants

Although most flowering plant species are hermaphrodites, there are still a large number of species with unisexual flowers. Classical geneticists identified the genes that distinguish the sexes in many species, but, until recently, nothing was known about the molecular mechanisms involved. Knowledge of the genes that control floral organ identity in a broad range of angiosperms has now allowed detailed comparative expression studies. Intriguingly, the sex-related differences indicate that the mechanism of sex determination is not the same in all species. In addition, genes that affect the sexual expression of flowers have been cloned from maize, and the sequences of these indicate that they are involved in hormone metabolism.