Calcium imaging of the cyclic nucleotide response.

Calcium (Ca(2+)) 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 Ca(2+)([Ca(2+)]cyt) is an early event in the response of stomata to both opening and closing stimuli, and cyclic nucleotide-mediated Ca(2+) signalling has been implicated in the regulation of stomatal aperture. A range of techniques have been used to measure [Ca(2+)]cyt in plant cells. Here we describe a potential method for imaging cyclic nucleotide-induced changes in [Ca(2+)]cyt in guard cells using the cameleon ratiometric Ca(2+) reporter protein.