Figure 5.

Modified ABC Model for L. schismatica Based on Expression Data Reported Here and Compared with the ABC Model of Arabidopsis.

(A) The combinatorial ABC model of flower organ identity conserved among eudicots, with B function restricted to the petal and stamen primordia (Coen and Meyerowitz, 1991).

(B) Proposed molecular genetics hypothesis to explain the inside-out flower of L. schismatica: AP3-PI dimer function is restricted to the flower center, where stamens initiate and develop. A (green), B (AP3 dark blue and PI light blue), and C (orange) function. CA, carpels; PE, petals; SE, sepals; ST, stamens; TE, tepals. Bar = 500 μm.

(C) Changes in the in situ expression patterns of B gene mRNA along flower developmental series comparing Arabidopsis (Jack et al., 1992; Goto and Meyerowitz, 1994; Krizek and Meyerowitz, 1996) and L. schismatica (this article). The differences between these two species represent two instances of the evolutionary shifts of such patterns during angiosperm evolution. Schematic representation of the developmental stages of Arabidopsis and L. schismatica flowers, starting at stage 3 of Arabidopsis flower development when sepal primordia are already visible. Sepal primordia continue to grow until they enclose the flower meristem, from stage 4 to 6. Meanwhile, at stage 5, petal and stamen primordia start to appear, and the gynoecium starts to form at stage 6. Similar stages of L. schismatica flower development were selected based on morphological traits.

[See online article for color version of this figure.]