Figure 2.

Regulatory pathways of epidermal cell fate specification, differentiation, and morphogenesis. Trichomes (magenta), pavement cells (gray), and stomata (green) as well as stomatal precursor cells (meristemoids, jade green, GMCs, light green) are all originated from protodermal cells (white). Genes (dark gray) and key regulatory components (blue) specifying each process (activation as arrows; inhibition as T-bars) are indicated. Solid arrows/T-bars represent known direct regulation, and dotted arrow/T-bars represent indirect relationships. Stomatal differentiation program gives rise to SLGCs (light gray) which can generate both pavement cells and stomatal precursors, and are therefore placed in between these two developmental programs. For details of individual genes and cellular processes, see the text. Fate Specification: a process in which an undifferentiated precursor cell acquires a specific fate. Differentiation: a process whereby a given cell becomes a specific (different) cell type. Morphogenesis: a cellular process to elaborate specific cell shape, size, and morphology to function as a specific cell type.