Stomatal Patterning

Abstract Stomatal development is a model for understanding the integration of multiple inputs into a simple cell fate choice. Intense research during the past decade has revealed mechanisms that govern stomatal development including inter‐ and intracellular signalling, transcriptional regulation, cell polarisation and asymmetric cell divisions. Recent discoveries in Arabidopsis include conserved families of transcription factors that drive differentiation and morphogenesis in the stomatal lineage. Specific proteins and pathways that mediate the transduction of signals, and thereby contribute to fate decisions such as secreted protein ligands, receptor kinases, mitogen activated protein kinase kinases and light and hormones have also recently been described. Studies in Arabidopsis and maize revealed novel proteins polarised within dividing stomatal lineage precursors. Together, these discoveries set the foundation to untangle mechanisms that lead to pattern and cell fate acquisition in plant systems. Key Concepts: Stomata are cellular pores that regulate gas exchange in plant leaves. Stomatal density and distribution is modulated by the environment and responds to changes in light, CO 2 and humidity. Stomatal development provides a framework for the understanding of cell fate, cell–cell signalling and cell polarity in plants. Progression through the stages of stomatal development in Arabidopsis requires a balance of fate promoting transcription factors, and fate and division repressing cell–cell signalling. Based on genetic studies, plants and animals display considerable conservation in the molecules and mechanisms used for developmental fates, but plant‐specific modules are used to generate physically asymmetric cell divisions that characterise early stomatal development.