Fig. 9. Model of meristem identity transition. The transcription factor LFY directly activates three known meristem identity regulators: AP1, CAL and LMI1. LFY and LMI1 together activate CAL directly in a feed-forward loop network motif. CAL is known to act upstream of AP1. LMI1 is upregulated by another unknown factor (indicated as X) in addition to LFY. LMI1 also has a LFY-independent role in meristem identity (dashed arrow from LMI1). Additional direct LFY targets are known (arrow from LFY) that may also play a role in meristem identity. Dashed arrows indicate direct or indirect effects, solid arrows indicate a direct effect. Developmental time is indicated along the vertical axis.