FIGURE 2.

Meristem identity genes in Arabidopsis. (A) Images of wild-type (WT) and tfl1 mutant plants. While in the WT the main inflorescence and the lateral inflorescences (appearing in the axil of cauline leaves) show indeterminate growth, in the tfl1 mutant the main inflorescence ends into a terminal flower (a fruit in this image) and lateral branches are replaced by solitary flowers. (B) Inflorescence of an ap1 mutant. Individual flowers are replaced by branched structures. (C) Diagrams of meristem identity in the inflorescences of the wild-type and the tfl1 and ap1 mutants. In tfl1, the indeterminate inflorescence apex (I) is replaced by a terminal flower (F) while in ap1, the flowers are replaced by inflorescence-like structures. Arrowheads, indeterminate shoot; open circles, flowers, closed circles, abnormal flowers. (D) Model for specification of meristem identity in the simple inflorescence of Arabidopsis. In the Arabidopsis inflorescence apex, TFL1 expression in the inflorescence meristem (I) and AP1 and LFY expression in the floral meristem (F) are required for these meristems to acquire their identity. Expression of these genes in their correct domains is maintained by mutual repressive interactions.