Antagonistic regulation of the meristemoid-to-guard mother-cell-transition.

Laura Serna

doi:10.3389/fpls.2013.00401

Abstract

The building of a multicellular organism from a single cell is the result of coordinated acquisition of different cell identities in an ordered spatial arrangement. But, how do cells learn about their identity? Stomatal development in Arabidopsis provides perhaps one of the most tractable contexts in which to examine concepts of cell fate determination, as a variety of lineage tracing techniques, including long-term confocal time lapse imaging (Peterson and Torii, 2012), can be deployed in different genetic contexts and environmental conditions to trace the history of only a few cell types. In this essay, I focus on the choice between meristemoid cell self-renewal, in which one of daughters of a dividing meristemoid retains the properties of the parent cell, and its transition through guard mother cell (GMC) fate to produce stomata.

Highlights

In Arabidopsis, stomatal development, which starts at the tip of the leaf and proceeds basipetally, takes place through a series of stereotyped yet flexible cell division pattern (Lau and Bergmann, 2012; Pillitteri and Torii, 2012)
Time-lapse confocal imaging in live leaves showed that the basic helixloop-helix factor SPEECHLESS (SPCH) locates in meristemoid mother cell (MMC) and meristemoids, and disappears in guard mother cell (GMC)
In addition to SPCH, MAPKs provide flexibility to stomatal development through repression of the meristemoidguard mother cell switch (Lampard et al, 2009): constitutive activation, beginning in meristemoids, of either the mitogenactivated protein kinases (MAPK) kinase kinase YODA (YDA) or the MAPK kinases MKK4, MKK5, MKK7 or MKK9 prevents stomatal formation giving rise to an epidermis consisting of pavement cells and arrested meristemoids

Summary

Introduction

In Arabidopsis, stomatal development, which starts at the tip of the leaf and proceeds basipetally, takes place through a series of stereotyped yet flexible cell division pattern (Lau and Bergmann, 2012; Pillitteri and Torii, 2012). Time-lapse confocal imaging in live leaves showed that the basic helixloop-helix (bHLH) factor SPEECHLESS (SPCH) locates in MMCs and meristemoids, and disappears in GMCs. This finding strongly suggests a role for SPCH, which drives the cell division that initiates the stomatal-cell lineage (MacAlister et al, 2007; Pillitteri et al, 2007), in the maintenance of meristemoid self-renewal activity in the leaves (Robinson et al, 2011). In addition to SPCH, MAPKs provide flexibility to stomatal development through repression of the meristemoidguard mother cell switch (Lampard et al, 2009): constitutive activation, beginning in meristemoids, of either the mitogenactivated protein kinases (MAPK) kinase kinase YODA (YDA) or the MAPK kinases MKK4, MKK5, MKK7 or MKK9 prevents stomatal formation giving rise to an epidermis consisting of pavement cells and arrested meristemoids.

Results

Conclusion