Stomagen positively regulates stomatal density in Arabidopsis.

Stomata are specialized structures in the epidermal layer of leaves that regulate the exchange of gases between the plant and the atmosphere. One or more positive intercellular signalling factors are assumed to be involved in stomatal development, but their identities remain elusive. A novel secretory protein — named stomagen — is now shown to be just such a factor; it is conserved among vascular plants and positively regulates stomatal density.