Intracellular Ca2+-uptake and its contribution to signalling

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Calcium is the most common second messenger in eukaryotic cells and it is generally assumed that specificity in Ca2+ signalling can be achieved by stimulus-specific, spatio-temporally distinct changes in cytosolic Ca2+ concentrations. Such Ca2+ signatures in response to different stimuli are the result of the combined and tightly regulated activities of channels and transporters that mediatein- and efflux of cytosolic Ca2+. Our objective is to understand how individual intracellular Ca2+-stores and transport systems contribute to the spatial and temporal characteristics of [Ca2+]cyttransients. We have added the so-called GECOs, a novel class of intensity based Ca2+ sensors with a very high dynamic range and available in different colours to the toolbox and are now able to generate a high-resolution atlas of both local and systemic Ca2+-responses in roots. Our particular focus will be to determine if and how release of vacuolar calcium contributes to Ca2+-signatures. By combinatorial expression of spectrally distinct GECOs we will be able to simultaneously measure Ca2+-dynamics in different compartments and by combining GECOs with sensors for ROS and pH we plan to elucidate the temporal and spatial relationships among these important signalling molecules. Furthermore, by cell-type specific and inducible expression of calcium decoys we plan to interfere with local and systemic Ca2+-responses.