Specification of stomatal fate in Arabidopsis: evidences for cellular interactions.

Stomata are bi-celled epidermal structures distributed in predictable patterns providing plants with pathways for gas exchange with the atmosphere. In Arabidopsis thaliana, stomatal formation is emerging as an elegant and powerful model system to study the genetic and molecular control of cell fate specification and pattern formation in multicellular organisms. In this review, we describe the mechanisms that regulate stomatal distribution in this model plant. The emerging view indicates that cellular interactions play a relevant role during stomatal pattern formation. These cellular interactions are not restricted to a cell layer and signalling within the epidermis, between the epidermis and the underlying tissues and between organs seem to play a relevant role during stomatal formation. Whatever the nature of the different signals, the stomatal pattern must arise as the result of the integration by the epidermal cells of multiple inputs. Uncovering the molecular nature of such signals and understanding the specific role during stomatal development provides a formidable task for the future.