Calcium Imaging of the Cyclic Nucleotide Response

Calcium (Ca²⁺ ) is a key component of the signalling network by which plant cells respond to developmental and environmental signals. A change in guard cell cytosolic free Ca²⁺ ([Ca²⁺ ]_cyt ) is an early event in the response of stomata to both opening and closing stimuli, and cyclic nucleotide-mediated Ca²⁺ signalling has been implicated in the regulation of stomatal aperture. A range of techniques have been used to measure [Ca²⁺ ]_cyt in plant cells. Here we describe a potential method for imaging cyclic nucleotide-induced changes in [Ca²⁺ ]_cyt in guard cells using the cameleon ratiometric Ca²⁺ reporter protein.