Biotechnological applications for stomatal guard cells

The highly specialized physiology and morphology of stomatal guard cells makes them an attractive choice for studying the processes involved in plant cell differentiation in vivo and in plant cell dedifferentiation in vitro. Recently, it has been independently demonstrated, using three contrasting systems, that guard cells are not terminally differentiated but can, under appropriate conditions, be induced to exit their normal developmental state and undergo additional rounds of cell division. Totipotency has also been confirmed for both Nicotiana glauca and Beta vulgaris guard cells and normal plants have been obtained from each. Ontogeny clearly confers function, but not destiny, even for this specialized cell type. Furthermore, a potentially valuable, new experimental tool has been identified for further use. These aspects will be discussed in relation to the planned exploitation of guard cell systems to extend our knowledge of processes fundamental to guard cell function and plant cell (de)differentiation and also for applications in plant biotechnology.