Multiple endogenous and environmental signals control when plants flower. In Arabidopsis, the LEAFY (LFY) transcription factor integrates these signals by activating the expression of several floral homeotic genes,including APETALA3 (AP3). Activation of AP3expression also requires the activity of UNUSUAL FLORAL ORGANS (UFO), an F-box component of an ubiquitin E3 ligase that labels proteins for proteasome-mediated degradation. Chae and colleagues now unexpectedly reveal that UFO regulates floral development in Arabidopsis by acting as a transcriptional co-factor (see p. 1235). They show that UFO interacts physically with LFY in vitro and in vivo, and that this interaction is needed to recruit UFO to the AP3 promoter. UFO engineered to act as a transcriptional repressor reduces endogenous LFY activity, they report, and the disruption of proteasome activity interferes with LFY-dependent AP3 activation. Together, these results suggest a new mechanism for regulating flower development in which UFO is a co-factor for LFY-induced AP3 transcription that regulates the activity of LFY in a proteasome-dependent manner.