Calcium, Mechanical Signaling, and Tip Growth
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Changes in cytosolic Ca2+ have emerged as important regulators of plant growth. During tip growth, changes in cytosolic Ca2+ appear to trigger proton fluxes and reactive oxygen species (ROS) production to the apoplast of the growing cell, likely to reinforce the wall to prevent uncontrolled expansion. In addition, ROS permeate to the cytosol to act as signals triggering a range of downstream processes, including Ca2+ channel gating. Thus, in a complex feedback process, the extent of the Ca2+ gradient at the growing tip is modulated to precisely control growth. These changes bear striking similarities to responses elsewhere in the plant to physical stimuli, where Ca2+, ROS, pH also all play roles in the mechanoresponse. Analyses of Ca2+-responsive signaling elements such as calmodulin and the CDPKs is beginning to reveal how such Ca2+ changes may be decoded to control growth. Networks of these Ca2+-response pathways tuned to “listen” to particular components of the Ca2+ signal may help explain how plants can so exquisitely integrate and entrain their responses to current environmental conditions to effect plastic development.
KeywordsReactive Oxygen Species Pollen Tube NADPH Oxidase Root Hair Pollen Tube Growth
This work was supported by grants from the National Science Foundation, National Aeronautics and Space Administration and United State Department of Agriculture.
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