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 differentiat ion, their target genes must be identified. In Arabidopsis flowers, th e homeotic protein heterodimer APETALA3/PISTILLATA is necessary for pe tal and stamen formation. Here, AP3/PI function was put under posttran slational control to analyze its immediate effect on the floral mRNA p opulation, with indirect effects blocked by cycloheximide. Using diffe rential display, a target gene of AP3/PI was identified (NAP: NAC-LIKE , ACTIVATED BY AP3/PI), which is homologous to genes required for meri stem establishment and separation of floral organs. The expression pat tern of NAP and the phenotypes caused by its mis-expression suggest th at it functions in the transition between growth by cell division and cell expansion in stamens and petals.