Simon Gilroy, University of Wisconsin, Madison, Stress makes waves: systemic signaling in Arabidopsis

Plants are exquisitely sensitive to their environment, rapidly integrating signals to appropriate developmental and physiological responses throughout the plant body. Changes in cytoplasmic Ca2+ are well recognized as signaling elements in plants and provide attractive candidates for part of this systemic signaling system. We have been able to visualize Ca2+ waves moving from the site of stress perception (such as local wounding or pathogen attack) to distant organs, where they facilitate systemic molecular responses. Ca2+ wave propagation occurs through specific tissues dependent on the eliciting stress and moves at rates of up to 1 mm/sec. We have been able to integrate the quantitation of the cellular kinetics of these waves in a range of mutants with modeling of cellular ion dynamics. These analyses highlight key roles for vacuolar ion transporters, such as the slow vacuolar channel TPC1 and the vacuolar Ca2+-ATPases, and the plasma membrane glutamate receptor-like channels. The modeling also indicates reactive oxygen species are important elements in the cell-to-cell transmission of systemic stress signals.