Science 321, 836–838 (2008)

Credit: SCIENCE

In about 4,000 species of flowering plant, individuals can grow both male and hermaphrodite flowers. This curious trait is called andromonoecy, and it has evolved on many separate occasions. Now, Abdelhafid Bendahmane of the National Institute for Agronomic Research in Evry, France, and his colleagues reveal the genetic mechanism behind this strategy in the melon Cucumis melo (pictured right).

They found that andromonoecy results from a single base change in a gene that encodes an enzyme that is involved in producing a hormone called ethylene. This hormone inhibits the development of a plant's male sex organs. Andromonoecious melons have two copies of the altered gene, and consequently produce less enzyme. This means that any female flowers they would otherwise have grown are turned into hermaphroditic blooms.