Reinforcing the idea of signalling in the stomatal pathway

Stomata are plant epidermal structures that regulate gas exchange with the atmosphere. In Arabidopsis, mutations in TOO MANY MOUTHS (TMM) disrupt a range of processes related to stomatal development and patterning. Recently, the sequence and the expression pattern of TMM were reported. TMM encodes a leucine-rich-repeat-containing, receptor-like protein that lacks a cytoplasmic kinase domain and that is expressed in postprotodermal cells. Several lines of evidence suggest that TMM and STOMATAL DENSITY AND DISTRIBUTION1, a putative subtilisin-like serine protease, might act in the same signalling pathway.