Genetic and Molecular Analysis of the Knotted (Knl) Gene in Maize

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The Knotted (Kn1) locus, defined by dominant mutations that affect leaf development, was cloned by transposon tagging. Subsequent sequence analysis demonstrated that Kn1 encodes a homeodomain, a DNA-binding motif encoded by a number of Drosophila developmental genes. While the dominant, gain-of-function mutations specifically affect the leaf, initial results demonstrate that in normal plants, the protein is abundant in meristems and not detectable in developing leaves. The present goal is to understand the wildtype function of the Kn1 gene using both genetic and molecular approaches. Loss of function mutations will be isolated in maize and the gene will be ectopically expressed in transgenic plants to evaluate the phenotype and functional domains of the gene. Unlinked suppressors will be isolated in Arabidopsis using either the maize gene or a putative Arabidopsis Kn1 homolog. Sequences bound by the Kn1 protein in vivo will be immunoprecipitated using a monoclonal antibody to determine what genes might be regulated by Kn1. Kn1 has many features expected of a key regulatory gene including the homeobox, meristematic expression, and provocative mutant phenotypes. Understanding how Kn1 functions may provide fundamental insight into the genetic control of plant development.