Early acting genes in stomatal development

In stomata early acting development genes that act early are able to control the asymmetric division of meristemoid cells. They are therefore able to directly control both the placement and the quantity of stomata that are produced. Much work has been done in Arabidopsis thaliana in the stomata field this has helped to identify many of the earlier acting genes; these include those which code proteins that act as as receptors, kinases and proteases.

Receptor mediated stomata genes

One of the genes that is involved in receptor mediated control of stomata development is TMM (Too Many Mouths). This gene was identified through a mutation that led to changes in asymmetric cell divisions and resulted in too many leaf stoma being produced. it was found that the mutant form of too many mouths resulted in a failure to control spacing divisions and to stop the division of cells adjacent to two stomata or precursor cells. Additionally of TMM led to reduction in amplification division, in turn producing more guard mother cells. TMM is thought to encode a cell surface receptor that is involved in asymmetric divisions and is expressed in guard mother cells and meristemoids, as well as daughter cells that produce meristemoids. It is thought that the gene acts with erecta family members to control the tissue specific regulation that underlies the formation of stomata.

MAP kinase signaling pathway genes that influence stomatal cell development

It is known that a MAP Kinase pathway is involved in stomatal development. A gene known as YODA is able to alter both the spacing and density of stomata. The YODA mutation leads to an increased production of guard cells. Mutations of this MAP kinase kinase kinase gene lead to an increase in entry divisions and a lack of spacing division alignment. Additionally YODA mutations often results in stomata having no adjacent reservoir cells between them.

In addition to MAP kinase pathways and receptor mediated mechanisms many other early acting genes are known to be involved in stomatal development. These include those that are involved in ligand interactions such as SDD1 and those that have a role in stem cell compartmentation.