In flowers, the conserved transcription factor AGAMOUS (AG) is important for reproductive organ development and for terminating stem cell maintenance,but how is its own activation controlled? Now, on , Jan Lohmann and co-workers reveal that the bZIP transcription factor PERIANTHIA (PAN)directly regulates AG in Arabidopsis. The researchers show that PAN binds to a highly conserved AG enhancer motif and is required for in vivo AG enhancer activity. AG expression levels usually do not change in pan mutants, indicating that other factors redundantly regulate AG expression, but they decrease when pan mutants are grown in shorter days, demonstrating that the regulatory circuitry of AG senses environmental influences. Conversely, in ag mutants, PAN expression continues for too long, suggesting that a negative-feedback loop exists between the two factors. A second study by Das, Meyerowitz and colleagues corroborates the role of PAN in regulating AG (see ). Based on their findings, the authors of both studies propose that PAN directly regulates AG expression as part of a redundant regulatory network.
