Floral Displays: Genetic Control of Grass Inflorescences

Inflorescences in angiosperms are complex structures that have many different types of meristems. Among complex inflorescences, the best studied are in the grass family. Multiple inflorescence genes have been cloned from grasses over the past few years, many of them by positional cloning using the rice genome as a source of positional information. Several genes affect the apical meristem of the inflorescence differently from the lateral branch meristems, allowing morphological differentiation that permits diversification. ramosa1 (ra1), ra2, and ra3 have been cloned from maize and form part of a network of genes that control the production of lateral branching. Curiously, only ra2 is widely conserved; to date, ra1 and ra3 have been found only in Andropogoneae. Additional domestication genes that affect the inflorescence have also been cloned from maize, rice, and wheat.