Molecular analysis of the SCARECROW gene in maize reveals a common basis for radial patterning in diverse meristems

Maize and Arabidopsis root apical meristems differ in several aspects of th eir radial organization and ontogeny. Despite the large evolutionary distan ce and differences in root radial patterning, analysis of the putative maiz e ortholog of the Arabidopsis patterning gene SCARECROW (SCR) revealed expr ession localized to the endodermis, which is similar to its expression in A rabidopsis. Expression in maize extends through the quiescent center, a pop ulation of mitotically inactive cells formerly thought to be undifferentiat ed and to lack radial pattern information. Zea mays SCARECROW (ZmSCR), the putative maize SCR ortholog, was used as a molecular marker to investigate radial patterning during regeneration of the root tip after either whole or partial excision. Analysis of the dynamic expression pattern of ZmSCR as w ell as other markers indicates the involvement of positional information as a primary determinant in regeneration of the root radial pattern.