(1) Class 1 knox genes are expressed in shoot meristems and are down-regulated as leaves initiate. Loss of function mutations reveal that knox genes are important for meristem maintenance and internode patterning. Gain of function mutations suggest that knox genes regulate determinacy. We are using biochemistry, expression profiling and genetic screens to identify the targets of knox genes in maize and Arabidopsis.

(2) Maize has two distinct inflorescence structures, the tassel and ear. Both of these produce floral meristems from determinate branches called spikelets. A number of maize mutations affect determinacy of the spikelet meristem; branching structures form instead of flowers in these mutants. Isolation of these genes provides a useful tool for studying meristem fates and for comparative studies in other grasses. For example, both the sequence and expression pattern of branched silkless1 are conserved in all the grasses we have examined.

(3) Isolation of morphological mutants in maize provides a means for understanding developmental processes. New mutants we are investigating include Wavy auricles in blade (Wab) and milkweed pod (mwp). Wab defines a lateral domain in the leaf that is required for proper coordination between the proximal/distal and medial/lateral axes. The mwp mutant was originally discovered by Oliver Nelson and affects husk leaf development.