Figure 1.

Cell State Transitions in Stomatal Development and the Transcription Factors That Promote These Transitions.

(A) Three state transitions occur in stomatal development. These require the Arabidopsis SPEECHLESS (transition 1), MUTE (transition 2), FAMA, FOUR LIPS, and MYB88 (transition 3) transcription factor genes. In the diagram of the MMC, the meristemoid cell is shaded gray, and the larger stomatal lineage ground cell cell is unshaded.

(B) Tracings of the wild type and mutant epidermis showing effects of loss-of-function mutations in the speechless, mute, fama, four lips, and myb88 loci and in the MAP kinase pathway and the effect of overexpression of the SPEECHLESS, MUTE, and FAMA genes and constitutively active kinases.