1. Stomata – Development Philipp Gerke PCDU-Seminar 16.12.2015

2. Stomata Development – Cell State Transition bHLHs = basic helix-loop-helix Transcription factors SPCH, MUTE, FAMA Are key switches partial expressed SCREAMs/ICEs Maintenance for development Consecutive expressed SLGC MYB transcription factors: Part of the cell cycle machinery MYB88 Four lips (FLP) Counterpart of FAMA

3. Stomata Patterning – One Cell Spacing Rule One cell spacing rulecell-cell communication via short distance signals SLGC 1.SLGC are dividing away from existing stomata 2.Two misplaced meristemoids next to each other divides away from each other

4. Leucin Rich Repeat Receptor Like Kinases (LRR-RLK) Ligand binding domain Kinase domain Over 200 members in Plants Single pass trans membrane proteins Forms functional homo- and heterodimers Members involved in stomatal development: ERECTAexpressed in protodermal cells ERL1 expressed in meristemoids GMCs and young GCs ERL2 TMMexpressed across the stomatal lineage lacking the kinase domain

5. Epidermal Patterning Factor Like (EPFL) Family 11 members in this family Secreted cysteine-rich peptides ~50-90 amino acid Characteristic intramolecular disulfid bonds Members involved in stomatal development: EPF1secreted by late meristemoids and GMCs EPF2secreted by MMCs and early meristemoids EPFL9 (Stomagen)secreted by mesophyll tissue obove the epidermis

6. Receptor Ligand Interaction Treatment with Arrested meristemoids Only pavement cells EPF2/ERECTA prevents surrounding protodermal cells to perform a entry division EPF1/ERL1 promotes a the correct spacing and repress meristemoids differentiation

7. Receptor Ligand Interaction Mesophyll tissue Stomagen has a positive influence on stomata development

8. Phytohormones Signal transduction from the cell membrane to the nucleus Photosynthetic tissue Surrounding epidermis cells MAPK Cascade: Also present in yeast and animals Activation by sequential phosphorylation of 3 kinase modules Deactivation of SPCH via phosphorylation MAPK Cascade is an integration point of other developing signals Temperature ? CO 2 HIC proteins

9. Asymmetric cell division and division polarity Problems … no recognizable homologs of animal or fungal polarity genes ! … the mechanical restrictions of the cell wall Plant specific polarity genes were identified BASL and POLAR

10. Conclusion Stomata are produced through a characteristic series of divisions controlled via the coordinated activities of transcription factors that can directly regulate core cell-cycle genes. Correct stomatal patterning and initiation requires intercellular communication through the activity of secreted peptide ligands, receptor kinases, and MAPK signaling modules. Environmental conditions impact the production of stomata in developing leaves via a long- distance signal initiated in mature leaves. MAPK modules may provide a common integration point among multiple environmental inputs. Polarity localized proteins (BASL and POLAR) provide the first examples polarity factors in plants.

11. References Facette, Michelle R.; Smith, Laurie G. (2012): Division polarity in developing stomata. In: Current Opinion in Plant Biology 15 (6), S. 585–592. DOI: 10.1016/j.pbi.2012.09.013. Lau, On Sun; Bergmann, Dominique C. (2012): Stomatal development: a plant's perspective on cell polarity, cell fate transitions and intercellular communication. In: Development (Cambridge, England) 139 (20), S. 3683–3692. DOI: 10.1242/dev.080523. Pillitteri, Lynn Jo; Torii, Keiko U. (2012): Mechanisms of stomatal development. In: Annual Review of Plant Biology 63, S. 591–614. DOI: 10.1146/annurev-arplant-042811-105451. Simmons, Abigail R.; Bergmann, Dominique C. (2015): Transcriptional control of cell fate in the stomatal lineage. In: Current Opinion in Plant Biology 29, S. 1–8. DOI: 10.1016/j.pbi.2015.09.008. Torii, Keiko U. (2012): Mix-and-match: ligand-receptor pairs in stomatal development and beyond. In: Trends in Plant Science 17 (12), S. 711–719. DOI: 10.1016/j.tplants.2012.06.013.