A bZIP factor, TRAB1, interacts with VP1 and mediates abscisic acid-induced transcription

The transcription factor VP1 regulates maturation and dormancy in plant see ds by activating genes responsive to the stress hormone abscisic acid (ABA) . Although activation involves ABA-responsive elements (ABREs), VP1 itself does not specifically bind ABREs. Instead, we have identified and cloned a basic region leucine zipper (bZIP) factor, TRAB1, that interacts with both VP1 and ABREs. Transcription from a chimeric promoter with GAL4-binding sit es was ABA-inducible if cells expressed a GAL4 DNA-binding domain::TRAB1 fu sion protein. Results indicate that TRAB1 is a true trans-acting factor inv olved in ABA-regulated transcription and reveal a molecular mechanism for t he VP1-dependent, ABA-inducible transcription that controls maturation and dormancy in plant embryos.