Genetic and molecular analysis of patterning in plant development.

Phyllotaxy, or leaf arrangement, and leaf shape are two products of patterning mechanisms in plants. We have isolated a family of plant homeobox genes that provide tools to study both of these components. Expression patterns of the homeobox genes appear to predict leaf initiation sites; the ectopic expression of these genes affects leaf shape. We have isolated a recessive mutation, abphyl, that changes the phyllotaxy of maize from alternate to opposite. Analysis of mutant plants suggests that the gene product regulates meristem size. We consider the possible roles of gene expression and physical constraints in establishing pattern.