CamelliA-based simultaneous imaging of Ca(2+) dynamics in subcellular compartments

As a universal second messenger, calcium (Ca(2+)) transmits specific cellular signals via a spatiotemporal signature generated from its extracellular source and internal stores. Our knowledge of the mechanisms underlying the generation of a Ca(2+) signature is hampered by limited tools for simultaneously monitoring dynamic Ca(2+) levels in multiple subcellular compartments. To overcome the limitation and to further improve spatiotemporal resolutions, we have assembled a molecular toolset (CamelliA lines) in Arabidopsis (Arabidopsis thaliana) that enables simultaneous and high-resolution monitoring of Ca(2+) dynamics in multiple subcellular compartments through imaging different single-colored genetically encoded calcium indicators. We uncovered several Ca(2+) signatures in three types of Arabidopsis cells in response to internal and external cues, including rapid oscillations of cytosolic Ca(2+) and apical plasma membrane Ca(2+) influx in fast-growing Arabidopsis pollen tubes, the spatiotemporal relationship of Ca(2+) dynamics in four subcellular compartments of root epidermal cells challenged with salt, and a shockwave-like Ca(2+) wave propagating in laser-wounded leaf epidermis. These observations serve as a testimony to the wide applicability of the CamelliA lines for elucidating the subcellular sources contributing to the Ca(2+) signatures in plants.