Novel and expanded roles for MAPK signaling in Arabidopsis stomatal cell fate revealed by cell type-specific manipulations
by Lampard G. R., Lukowitz W., Ellis B. E., Bergmann D. C. (2009)
in Plant Cell 2009,21:3506-3517.
(PubMed Abstract | Publisher Full Text|PubMed Central Full Text) –
Figure 1.
Diagram of Stomatal Lineage Development and Gene Expression Patterns.
Arabidopsis stomatal development follows a three-step stereotyped pathway that involves a series of asymmetric and symmetric cell divisions. Entry into the stomatal lineage is negatively regulated by a MAPK module containing YDA (MAPKKK), MKK4 and MKK5 (MAPKKs), and MPK3 and MPK6 (MAPKs). Progression through the developmental pathway is positively influenced by sequentially acting bHLH transcription factors, SPCH, MUTE, and FAMA, which regulate entry (1), progression through (2), and terminal differentiation of guard cell development (3), respectively. The expression of green fluorescent protein (GFP)-tagged transcriptional reporters of each of SPCH (A), MUTE (B), andFAMA (C) coincides with each major developmental transition. Bars = 50 μm.
Abstract
Mitogen-activated protein kinase (MAPK) signaling networks regulate numerous eukaryotic biological processes. In Arabidopsis thaliana, signaling networks that contain MAPK kinases MKK4/5 and MAPKs MPK3/6 function in abiotic and biotic stress responses and regulate embryonic and stomatal development.
However, how single MAPK modules direct specific output signals without cross-activating additional downstream processes is largely unknown.
Studying relationships between MAPK components and downstream signaling outcomes is difficult because broad experimental manipulation of these networks is often lethal or associated with multiple phenotypes.
Stomatal development in Arabidopsis follows a series of discrete, stereotyped divisions and cell state transitions. By expressing a panel of constitutively active MAPK kinase (MAPKK) variants in discrete stomatal lineage cell types, we identified a new inhibitory function of MKK4 and MKK5 in meristemoid self-renewal divisions.
Furthermore, we established roles for MKK7 and MKK9 as both negative and (unexpectedly) positive regulators during the major stages of stomatal development. This has expanded the number of known MAPKKs that regulate stomatal development and allowed us to build plausible and testable subnetworks of signals. This in vivo cell type-specific assay can be adapted to study other protein families and thus may reveal insights into other complex signal transduction pathways in plants.
See the text: NCBI
Read the full article: The Plant Cell
PLANT STOMATA ENCYCLOPEDIA 
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