Control of Cellular Differentiation in Maize Leaves

Mature maize leaves exhibit a series of parallel veins that are surrounded by concentric rings of bundle sheath and mesophyll cells. To identify genes that control cellular differentiation patterns in the leaf, we have isolated a group of mutations that specifically disrupt the differentiation of a single cell-type. In bundle sheath defective (bsd) mutant plants, bundle sheath cells fail to differentiate yet mesophyll and all other leaf cell-types develop normally. Morphological and functional characterization of specific bsd mutants (bsd1, bsd2, bsd3, pg14 and g2) reveals that they differ in the degree to which bundle sheath cell differentiation is perturbed. Mutant analysis predicts roles for BSD gene products in normal development.