Fig. 7. Model for the co-ordinated regulation of floral organ identity regulators. (A) In stamen development, AG, AP3, PI and SEP3 are initially activated independently (grey arrows) (Ferrario et al., 2004; Zik and Irish, 2003a). LFY is responsible for the initial activation of AG, whereas early activation of AP3/PI occurs in areas of the meristem that express both LFY and UFO (Parcy et al., 1998). The AG, AP3, PI and SEP3 proteins (circles) function together in a complex to promote stamen development (Honma and Goto, 2001), and to amplify and maintain their own expression. Solid black arrows indicate direct interactions supported by ChIP; feedback activation of PI may be indirect (dashed arrow) (Honma and Goto, 2000). (B) The protein complex proposed to control carpel development contains AG and SEP3 (Honma and Goto, 2001). As in A, the initially independent expression of AG and SEP3 is maintained by a positive-feedback loop. In addition, CRC expression is reinforced, although CRC expression can promote carpel development independently of AG (indicated by the parallel grey arrow) (Alvarez and Smyth, 1999). As in A, interactions supported by ChIP are indicated by solid black arrows. The possibility that CRC might also promote AG activity is indicated by the dashed arrow with a question mark.