Interactions of the developmental regulator ABI3 with proteins identified from developing Arabidopsis seeds

The ABI3 locus is a major regulator of embryo development in Arabidopsis an d is essential for the simultaneous activation of the maturation pathway, a s well as repression of germination and seedling development. We used a two -hybrid screen in yeast in order to identify proteins that interact with AB I3. Four ABI3-interacting proteins (AIPs) were identified which showed spec ific in vivo and in vitro interactions with the C-terminal region of ABI3 t hat contains the B2 and B3 domains, previously shown to have DNA binding ac tivity. The expression characteristics of the genes encoding the AIPs have also been analysed in wild-type and abi3, lec1 and fus3 embryo mutants. Thi s analysis demonstrated differential expression of these genes during norma l embryo development and in the mutant lines. All the AIPs show homology to existing transcription factors and therefore they may function with ABI3 w ithin the network of transcriptional regulators that control embryo develop ment in Arabidopsis.