Editors' ChoicePlant biology

Pairing Up for Patterning

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Sci. Signal.  07 Feb 2012:
Vol. 5, Issue 210, pp. ec44
DOI: 10.1126/scisignal.2002926

The secreted EPIDERMAL PATTERNING FACTORs (EPFs) 1 and 2 and the cell surface receptors ERECTA, ERECTA-LIKE1 (ERL1), and TOO MANY MOUTHS (TMM) are required for proper development of stomata, epidermal gas-exchange valves, in the plant Arabidopsis thaliana. Using epitope-tagged proteins heterologously expressed in Nicotania benthamiana, Lee et al. demonstrate that EPFs bind to these receptors. From extracts of plants in which each putative ligand-receptor pair was transiently expressed, the authors coimmunoprecipitated EPF1-ERECTA, EPF1-ERL1, EPF2-ERECTA, EPF2-ERL1, or EPF2-TMM complexes; EPF1 did not bind to TMM. Tagged versions of the mature forms of the EPFs that were produced in bacteria and shown to have biological activity in an in vivo Arabidopsis assay bound to immobilized tagged receptors purified from N. benthamiana. Whereas EPF1 bound to ERECTA and ERL1 with similar kinetics, EPF2 exhibited greater saturation in binding to ERECTA compared with ERL1 and TMM. Using tagged versions of the proteins transiently expressed from their native promoters in Arabidopsis, the authors demonstrated that ERECTA and ERL1 formed both homodimers and heterodimers in vivo; TMM did not self-associate but formed heterodimers with ERECTA and ERL1. Genetic experiments supported a role for EPF2 signaling primarily through ERECTA and EPF1 through ERL1 in consecutive steps of stomata development. Based on the known complexity of the cooperative and antagonistic interactions between TMM and the ERECTA family receptors in stomata development and the observed formation of heterodimers, the authors propose that TMM may fine-tune signaling through the ERECTA receptors. Understanding the ligand-receptor specificity and receptor oligomerization properties of this system should facilitate investigation of their roles in stomatal development.

J. S. Lee, T. Kuroha, M. Hnilova, D. Khatayevich, M. M. Kanaoka, J. M. McAbee, M. Sarikaya, C. Tamerler, K. U. Torii, Direct interaction of ligand-receptor pairs specifying stomatal patterning. Genes Dev. 26, 126–136 (2012). [Abstract] [Full Text]