Barron, Yoshimi , Romanowsky, Shawn , Myers, Candace , Harper, Jeffrey .
Calcium Dependent Protein Kinases: A Critical Role in Pollen Tube Growth.
While all eukaryotes use calcium as a signaling molecule, there is considerable diversity in how calcium signals are created and decoded. In a model plant, Arabidopsis thaliana, the 67 kinases implicated in calcium signaling are not present in animal systems. 34 of these kinases belong to a family of calcium-dependent protein kinases (CPKs), which are defined by a unique structure in which a calmodulin-like domain is fused to the kinase domain. At least 10 CPKs are expressed in mature pollen, and at least half of those show evidence for a plasma membrane location. In a systematic analysis of pollen expressed CPKs, we identified a phenotype from a double mutation of CPK17 and CPK34 which results in short (“teeny weenie”) pollen tubes as well as a defect in a pollen-tube/ovule interaction. Through experimental intervention, we created double homozygous plants, which display an almost completely sterile phenotype (less than 1 seed/silique). This defect can be rescued through pollen-specific expression of CPK34-GFP, providing strong genetic evidence that CPKs are normally essential to a plant’s life cycle. The ability to complement the double mutant also provides the first opportunity for an in vivo evaluation of a CPK’s structure and function. Here we show that while CPK34’s N-terminal acylation sites are necessary for anchoring it to the plasma membrane, surprisingly, acylation is not required for CPK34’s essential function in pollen development. Nevertheless, other features of the N-terminal domain are still important for function, as shown by domain-addition experiments. Our working model is that the variable N-terminal domain mediates isoform specific protein-protein interactions, providing a mechanism by which different CPK isoforms regulate different cellular functions.
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1 - University of Nevada, Reno, Dept. of Biochemistry, 1664 N. Virginia St. MS200, Reno, NV, 89557, USA
2 - University of Nevada, Reno, Dept. of Biochemistry
calcium dependent protein kinase
protein kinase signaling
Presentation Type: ASPB Minisymposium
Location: International Ballroom South/Hilton
Date: Wednesday, July 11th, 2007
Time: 11:55 AM