Homeobox genes in the functioning of plant meristems

Abstract
The maize homeobox geneknotted1(kn1) is expressed in vegetative and floral meristems and is down-regulated at the site of primordia formation.kn1-related genes from maize and other species also show meristem-specific expression and offer additional tools for studying the activities of shoot meristems. Members of this gene family are expressed early in embryogenesis, providing molecular markers for meristem initiation. Ectopic expression of eitherkn1or a relatedArabidopsisgene,KNAT1, causes dramatic alterations inArabidopsisand tobacco leaf morphology. Most significantly, meristems form on the leaf, producing small shoots. We discuss whether the phenotypes can be interpreted as changes in positional information or timing of determination.