Flower development and evolution: new answers and new questions.

Certain genes have a way of rewarding continued study, as can be seen from the long histories of discoveries that have resulted from work on mammalian hemoglobin genes, on the Escherichia coli lacZ gene, and on many others. A plant gene that may fit this mold is the homeotic flower-development gene AGAMOUS (AG). In the past few years, study of the genetics and molecular genetics of this Arabidopsis thaliana gene and of its orthologues in other plant species has led to a stream of discoveries that have revealed some ofthe mechanisms and some ofthe complexity offlower development. Two recent papers (1, 2), one in this issue, describe a new level of regulation ofAG and raise new questions about the function and evolutionary history of this gene.