Plant biology

Generator of Stomata

Sci. Signal.  19 Jan 2010:
Vol. 3, Issue 105, pp. ec25
DOI: 10.1126/scisignal.3105ec25

Stomata are pores in leaf epidermis that allow the exchange of gases and water vapor between plant cells and the environment. Inhibitors of stomatal development have been identified and include EPIDERMAL PATTERNING FACTOR 1 (EPF1) and EPF2, both of which bind to the receptor-like protein TOO MANY MOUTHS (TMM). Sugano et al. have identified stomagen as a factor that promotes stomatal development in Arabidopsis thaliana. Stomatal density was increased by overexpression of STOMAGEN and decreased by RNA interference (RNAi) directed against STOMAGEN. The abundance of STOMAGEN was higher in immature leaves, stems, and buds compared with their mature counterparts. STOMAGEN was present in mesophyll tissues (where photosynthesis occurs), a distribution that contrasts with that of other factors that regulate stomatal development, which are typically found in epidermal tissues (where stomata are located). Fluorescently tagged STOMAGEN was present outside cells, suggesting that STOMAGEN is secreted from mesophyll tissues. STOMAGEN was processed from a 102–amino acid precursor to a 45–amino acid peptide (which the authors referred to as stomagen), which increased stomatal density when overexpressed or when externally applied. The ability of STOMAGEN to promote stomatal development required the basic helix-loop-helix transcription factor SPEECHLESS and the receptor-like protein TMM. The authors propose that stomagen may compete with EPF1 and EPF2 for binding to TMM and that stomagen provides a mechanism by which photosynthetic tissues can enhance stomatal development in the epidermis.

S. S. Sugano, T. Shimada, Y. Imai, K. Okawa, A. Tamai, M. Mori, I. Hara-Nishimura, Stomagen positively regulates stomatal density in Arabidopsis. Nature 463, 241–244 (2010). [PubMed]