The D-Domains of MKK7/9 Are Not Absolutely Necessary for CAMKK7/9 Functions in Stomatal Development.
(A) Protein schematic (left) and images of phenotypes associated with expressing CAMKK7 in the SPCH, MUTE, and FAMA stages of stomatal development as indicated.
(B) and (C) The cotyledon epidermis of plants expressing CAMKK7ΔD in the SPCH (B) and MUTE (C) stages generally have wild-type stomatal distribution.
(D) and (E) The cotyledon epidermis of plants expressing CAMKK7ΔD in the FAMA stage. The majority of these plants have wild-type stomatal development but occasionally have limited clusters of stomata.
(F) to (I) Cotyledon epidermis of plants expressing CAMKK9ΔD plants in the SPCH (F), MUTE (G), and FAMA ([H] and [I]) stages. CAMKK9ΔD has impacts on stomatal development in the same fashion as CAMKK7ΔD.
The relative activity of each kinase variant in in vitro kinase assays is depicted as follows (+, less active than full length; ++, comparable activity to the full-length CAMKK). Hashed boxes in schematic representations of kinase variants indicate the region(s) that were removed. All images are of 10-DPG abaxial cotyledons, and bars = 25 μm.
Manipulation of Mitogen-Activated Protein Kinase Kinase Signaling in the Arabidopsis Stomatal Lineage Reveals Motifs That Contribute to Protein Localization and Signaling Specificity
by Lampard G. R., Wengier D. L., Bergmann D. C. (2014)
in Plant Cell 2014 Aug; pii: tpc.114.127415. [Epub ahead of print] –
http://www.ncbi.nlm.nih.gov/pubmed/?term=25172143
Abstract
When multiple mitogen-activated protein kinase (MAPK) components are recruited recurrently to transduce signals of different origins, and often opposing outcomes, mechanisms to enforce signaling specificity are of utmost importance. These mechanisms are largely uncharacterized in plant MAPK signaling networks.
The Arabidopsis thaliana stomatal lineage was previously used to show that when rendered constitutively active, four MAPK kinases (MKKs), MKK4/5/7/9, are capable of perturbing stomatal development and that these kinases comprise two pairs, MKK4/5 and MKK7/9, with both overlapping and divergent functions.
We characterized the contributions of specific structural domains of these four “stomatal” MKKs to MAPK signaling output and specificity both in vitro and in vivo within the three discrete cell types of the stomatal lineage.
These results verify the influence of functional docking (D) domains of MKKs on MAPK signal output and identify novel regulatory functions for previously uncharacterized structures within the N termini of MKK4/5. Beyond this, we present a novel function of the D-domains of MKK7/9 in regulating the subcellular localization of these kinases.
These results provide tools to broadly assess the extent to which these and additional motifs within MKKs function to regulate MAPK signal output throughout the plant.
See the text: NCBI
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