Flowering plants release copious amounts of sperm-carrying pollen to be delivered by wind, insect, or other carriers to waiting females. In some situations, the females are choosy about which pollen grains they allow to fertilize their eggs. How do these females discriminate between pollen types?
This month in the Journal of Heredity, Plant Biology scientist Matthew Evans together with Jerry Kermicle from the University of Wisconsin describe the inheritance of naturally occurring alleles of the maize gametophyte factor2 (ga2) gene and the distribution of these alleles in domesticated maize (the familiar corn plant) and its wild relative teosinte (a weedy plant that grows wild throughout Mexico). Maize and teosinte, while they look very different, are members of the same species and can interbreed. Certain alleles of the ga2 gene allow maize plants to select between different sperm donors within the same species. These same alleles of ga2 also provide a competitive advantage to pollen grains carrying them when fertilizing the appropriate females. The set of diverse ga2 alleles sets up a system of reproductive isolation between plants of the same species. Understanding how the ga2 system works will help us understand how new species arise and how genes flow between natural populations. This system may also prove useful in controlling the spread of transgenes between crop species and their relatives.
Journal of Heredity: The Zea mays Sexual Compatibility Gene ga2: Naturally Occurring Alleles, Their Distribution, and Role in Reproductive Isolation
Genetics.org: Analysis of stunter1, a Maize Mutant with Reduced Gametophyte Size and Maternal Effects on Seed Development