Submitted to: Proceedings of the National Academy of Sciences
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/1997
Publication Date: N/A
Citation: Interpretive Summary: In eastern gamagrass, sexes, male and female, are separated within an individual inflorescence whereas in maize the sexes are separated into different plant parts: tassels and ears. Despite these differences, the sex determining process appears to function through a common mechanism, i.e., induced pistil abortion controlled by a single regulatory gene common nto both maize and eastern gamagrass. This shared trait indicates that sex determination studies in maize will have important evolutionary and mechanistic implications for understanding the forces of natural selection that resulted in separation of the sexes in the grass family.
Technical Abstract: Cultivated maize (Zea mays) and several other members of the Tribe Andropogoneae produce unisexual florets. In maize, the formation of two staminate florets in each spikelets on the tassel and a single pistillate floret in each spikelet on the ear includes a pistil abortion process that requires the action of the TASSELSEED2 gene. In eastern gamagrass (Tripsacum dactyloides) the GYNOMONOECIOUS SEX FORM1 gene appears to perform a similar role in pistil abortion. These genes were shown to be homeologs by restriction fragment length polymorphism mapping and by the failure of the gsf1 and ts2 alleles to complement one another in intergeneric hybrids. Molecular analysis of the gsf1 allele shows that it is caused by a 1.4-kb deletion mutation. Both TASSELSEED2 and GYNOMONOECIOUS SEX FORM1 show similar expression patterns in subepidermal cells of pistils just before abortion. These results suggest that the formation of staminate florets in the Andropogoneae represents a monophyletic trait.