THE MADS DOMAIN PROTEIN AGL15 LOCALIZES TO THE NUCLEUS DURING EARLY STAGES OF SEED DEVELOPMENT

Little is known about regulatory factors that act during the earliest stages of plant embryogenesis. The MADS domain protein AGL15 (for AGAM OUS-like) is expressed preferentially during embryogenesis and accumul ates during early seed development in monocotyledonous and dicotyledon ous flowering plants. AGL15-specific antibodies and immunohistochemist ry were used to demonstrate that AGL15 accumulates before fertilizatio n in the cytoplasm in the cells of the egg apparatus and moves into th e nucleus during early stages of development in the suspensor, embryo, and endosperm. Relatively high levels of AGL15 are present in the nuc lei during embryo morphogenesis and until the seeds start to dry in Br assica, maize, and Arabidopsis. AGL15 is associated with the chromosom es during mitosis, and gel mobility shift assays were used to demonstr ate that AGL15 binds DNA in a sequence-specific manner. To assess whet her AGL15 is likely to play a role in specifying the seed or embryonic phase of development, AGL15 accumulation was examined in Arabidopsis mutants that prematurely exit embryogenesis. lec1-2 mutants show an em bryo-specific loss of AGL15 at the transition stage, suggesting that A GL15 interacts with regulators in the leafy cotyledons pathway.