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 and is essential for the simultaneous activation of the maturation pathway, as well as repression of germination and seedling development. We used a two-hybrid screen in yeast in order to identify proteins that interact with ABI3. Four ABI3-interacting proteins (AIPs) were identified which showed specific in vivo and in vitro interactions with the C-terminal region of ABI3 that contains the B2 and B3 domains, previously shown to have DNA binding activity. The expression characteristics of the genes encoding the AIPs have also been analysed in wild-type and abi3, lec1 and fus3 embryo mutants. This analysis demonstrated differential expression of these genes during normal embryo development and in the mutant lines. All the AIPs show homology to existing transcription factors and therefore they may function with ABI3 within the network of transcriptional regulators that control embryo development in Arabidopsis.