Figure 2.

Model for the Light Regulation of Stomatal Development and Patterning.

COP1 activates the YDA-MKK4/5-MAPK3/6 cascade to mediate protein degradation of SPCH and ICE1, or directly mediates the degradation of ICE1. How COP1 regulates YDA remains an intriguing question to be elucidated. Meanwhile, PIF4 represses transcription of SPCH and GNC/GNL that promotes stomatal development through upregulating the expression of SPCH. In conditions of light, red- and far-red light photoreceptors (phyB and phyA) and blue-light photoreceptors CRY1/2 act in concert to suppress COP1 and PIF4 activity and the associated downstream networks, thus promoting stomatal development. Besides, light promotes transcription and protein abundance of AN3, likely through the photoreceptor-mediated pathways, which then repress the expression of COP1 and YDA. Arrow and bar-ended lines represent activation and inhibition, respectively. Solid lines indicate direct regulation. Dotted lines indicate indirect regulation or through an unidentified mechanism.