Floral transcription factor AGAMOUS interacts in vitro with a leucine-richrepeat and an acid phosphatase protein complex

We are interested in identifying potential protein interactors of MADS doma in transcription factors during Arabidopsis thaliana flower development. We based our biochemical search on a conserved motif in the MADS domain that includes putative phosphatase and phosphorylation sites that may mediate pr otein interactions. An affinity column with this motif and a few surroundin g hypervariable amino acids derived from the AGAMOUS sequence was prepared and used to isolate potential interactors from floral crude extracts. Only two proteins were specifically bound to the affinity column. The first corr esponds to a carpel specific storage protein, VSP1, that presents acid phos phatase activity, and the second is a novel leucine-rich repeat protein tha t we have named FLOR1. Coimmunoprecipitation, two-hybrid yeast, and affinit y column assays show that the FLOR1-VSP1 complex interacts with AGAMOUS and that this transcription factor directly interacts with FLOR1. This is the first assay to show an interaction between plant MADS domain factors and no n-MADS proteins. (C) 2001 Academic Press.