A Homolog of NO APICAL MERISTEM is an Immediate Target of the Floral Homeotic Genes APETALA3/PISTILLATA

To understand how homeotic genes affect morphogenesis and differentiation, their target genes must be identified. In Arabidopsis flowers, the homeotic protein heterodimer APETALA3/PISTILLATA is necessary for petal and stamen formation. Here, AP3/PI function was put under posttranslational control to analyze its immediate effect on the floral mRNA population, with indirect effects blocked by cycloheximide. Using differential display, a target gene of AP3/PI was identified (NAP:NAC-LIKE, ACTIVATED BY AP3/PI), which is homologous to genes required for meristem establishment and separation of floral organs. The expression pattern of NAP and the phenotypes caused by its misexpression suggest that it functions in the transition between growth by cell division and cell expansion in stamens and petals.