Genes involved in stomatal patterning

Stomata can be thought of as valves that allow a plant to control the intake of carbon dioxide and to control water retention. They develop by a cell linage that produces meristemoids and guard cells. The stomata cell linage is responsible for most of the epidermal content of a plant, with cells from the lineage being able to divide to produce stomata or non-stomata containing tissue.

Many genes are involved in the production of epidermal tissue and stomata. The earlier acting genes act to control the asymmetric divisions of the meristemoid and are responsible for the final number and the patterning of the stomata that are produced. Later acting genes are more involved in halting the production of the stomata and of its morphogenesis.

Stomata patterning

Stomata are generally separated by at least one other cell. Theses cells act as reservoirs for solutes and enables stomata to act on an individual basis. These cells are produced by asymmetrical divisions of cells next to storna. This pattern of stomata spacing enables optimisation of gas and water diffusion. The division that takes place to produce the daughter cell requires that division is attuned so that the mew cell wall is not next to the stoma.

The patterning of stomata is dependent upon spatial cues; this enables them to be adjusted correctly within the epidermal. It is thought that patterning is influenced by intercellular signalling through the apoplasm. Many cells in the epidermal tissue are controlled by lateral inhibition (eg trichomes, root hairs); this is not the case with stomata as neighboring cells are able to acquire their own cell fate. A type of secondary spacing may also also occur in some plant species such as Arabidopsis, this produces an inward spiral that is not invariant.

Many genes have been shown to control stomatal development in Arabidopsis; they are thought to act by controlling the patterning and quantity of asymmetric stomatal cell divisions.
These early acting genes will be discussed in the next section.