CONTROL OF ARABIDOPSIS FLOWER AND SEED DEVELOPMENT BY THE HOMEOTIC GENE APETALA2

APETALAB (AP2) plays a central role in the establishment of the floral meristem, the specification of floral organ identity, and the regulat ion of floral homeotic gene expression in Arabidopsis. We show here th at in addition to its functions during flower development, AP2 activit y is also required during seed development. We isolated the AP2 gene a nd found that it encodes a putative nuclear protein that is distinguis hed by an essential 68-amino acid repeated motif, the AP2 domain. Cons istent with its genetic functions, we determined that AP2 is expressed at the RNA level in all four types of floral organs-sepals, petals, s tamens, and carpels-and in developing ovules. Thus, AP2 gene transcrip tion does not appear to be spatially restricted by the floral homeotic gene AGAMOUS as predicted by previous studies. We also found that AP2 is expressed at the RNA level in the inflorescence meristem and in no nfloral organs, including leaf and stem. Taken together, our results s uggest that AP2 represents a new class of plant regulatory proteins th at may play a general role in the control of Arabidopsis development.