Plant & Animal Genome VI Conference

S19

THE EVOLUTION OF MAIZE: FROM QTLS TO GENES

Plant Biology Department, University of Minnesota, St. Paul, MN 55108 USA

Maize and its wild progenitor, teosinte, differ dramatically in inflorescence and plant architecture despite the fact that their evolutionary divergence occurred within the past 10,000 years. The evolution of these differences involved a small number of loci of large effect. One of these loci, teosinte branched1 (tb1), largely controls differences in plant architecture. We have molecularly cloned tb1. tb1 shows sequence homology to the cycloidea gene of snapdragon, which has been hypothesized to function in the regulation of transcription. Based on the pattern of tb1 expression and its mutant phenotype, tb1 is hypothesized to act in part as a repressor of organ growth. The maize allele of tb1 is expressed at a higher level than the teosinte allele, suggesting a mechanism for the nature of the molecular changes responsible for phenotypic evolution. Specifically, the differences in plant architecture between maize and teosinte are modeled to result from differential repression/derepression organ growth as controlled in part by tb1.