14-3-3-PROTEIN ARE PART OF AN ABSCISIC-ACID VIVIPAROUS1 (VP1) RESPONSE COMPLEX IN THE EM PROMOTER AND INTERACT WITH VP1 AND EMBP1

Protein-DNA complexes were formed when nuclear extracts from embryogen ic rice suspension cultures or maize embryos were incubated with an ab scisic acid-VIVIPAROUS1 (VP1) response element (Emla) from the Em prom oter. Monoclonal antibodies generated to GF14, a 14-3-3 protein from p lants, resulted in gel retardation of the Emla-protein complexes. Anti bodies generated to the C and N termini of GF14 detected protein isofo rms in rice nuclear and cytoplasmic extracts, but no differences in di stribution of the GF14 isoforms were recognized between the nucleus an d cytoplasm or when abscisic acid-treated and untreated tissues were c ompared. When recombinant GF14 fusion proteins from rice were added to nuclear extracts, novel complexes were formed that required the dimer ization domain of GF14, Chemical cross-linking showed that GF-14 inter acted with the basic leucine zipper factor EmBP1, which binds specific ally to Em1a, and with VP1, which transactivates Em through Em1a. GF14 proteins from rice were shown to interact with VP1 in yeast through t he dimerization domain of GF14. Our results indicated that GF14 intera cts with both site-specific DNA binding proteins (i.e., EmBP1) and tis sue-specific regulatory factors (i.e., VP1) and may provide a structur al link between VP1 and the Emla transcriptional complex.