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IN BRIEF

A Complete MAPK Signaling Cascade That Functions in Stomatal Development and Patterning in Arabidopsis

neckardt{at}aspb.org

Stomatal development in Arabidopsis is preceded by asymmetric cell divisions, and stomatal distribution follows the one-cell spacing rule, which dictates that there is at least one pavement cell between two adjacent stomata. This reflects intercellular communication and coordination of cell fate specification between adjacent cells. Stomatal development and patterning are regulated by both genetic and environmental signals, but the regulatory mechanisms controlling these events have not been fully characterized. Wang et al. (pages 63–73) report that two environmentally responsive mitogen-activated protein kinases (MAPKs) in Arabidopsis, MPK3 and MPK6, and their upstream MAPK kinases (MAPKKs), MKK4 and MKK5, respectively, are key regulators of stomatal development and patterning. Previous studies have demonstrated that MKK4 and MKK5 are upstream kinases for MPK3 and MPK6 in a stress-responsive signaling cascade. Wang et al. show that the MPK3/MPK6-MKK4/MKK5 MAPK module functions as a negative regulator of the stomatal development pathway. Loss of function of these genes disrupted the coordinated cell fate specification of stomata versus pavement cells, resulting in the formation of clustered stomata. Conversely, constitutive activation of MKK4/MKK5-MPK3/MPK6 caused the suppression of asymmetric cell divisions and stomatal cell fate specification, resulting in lack of stomatal differentiation. In addition, the authors determined that the MKK4/MKK5-MPK3/MPK6 module functions downstream of the MAPKK kinase YDA, thus establishing a complete MAPK signaling cascade controlling stomatal development and patterning. This work suggests that the MPK3/MPK6 MAPK cascade functions as an integrating point of environmental and developmental signals regulating stomatal development.

View larger version (103K): [in this window] [in a new window] [as a PowerPoint slide]   Loss of function of MKK4/MKK5 or MPK3/MPK6 disrupts the coordinated cell fate specification of stomata versus pavement cells, resulting in the formation of clustered stomata.

www.plantcell.org/cgi/doi/10.1105/tpc.107.190110

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Stomatal Development and Patterning Are Regulated by Environmentally Responsive Mitogen-Activated Protein Kinases in Arabidopsis

Huachun Wang, Njabulo Ngwenyama, Yidong Liu, John C. Walker, and Shuqun Zhang
Plant Cell 2007 19: 63-73. [Abstract] [Full Text]  

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