The Horizon 2020 EU project Accelerated Development of multiple-stress tolerAnt PoTato (ADAPT), in which Europatat is participating, aims to elucidate potato tolerance to single and combined abiotic stresses, and to develop new strategies for potato improvement.
Small molecules such as calcium ions (Ca2+) or reactive oxygen species (ROS) play an essential role in transmitting early signals during the stress acclimation of plants. These molecules relay information on environmental changes into cellular responses such as changes in gene expression. As these signaling events play an important role in the regulation of plant stress acclimation, the understanding of how they function in detail (i.e. at the molecular level) under different conditions can help scientist to identify potential targets for future plant breeding, that shall eventually be used to generate new potato lines with improved stress resistance.
Moreover, since these secondary messengers send signals that can be observed at the very beginning of the acclimation process in plants, easy monitoring/visualization of their occurrence allows for implementation of counteracting measures before the detrimental effects of the stresses become visible. This could ultimately also be used in the field to optimize plant management practice by informing the farmer when exactly to apply which treatment (e.g. watering or applying fertiliser).
Potato sensor lines were thus developed within ADAPT for the aequorin-based measurement of Ca2+ transients (short term increases in free Ca2+ levels). In a collaboration between the University of Bonn, the FAU Erlangen and Durham University, aequorin-based sensor lines of potato and Arabidopsis were then used to analyse and compare Ca2+ transients in response to different abiotic and biotic stimuli using soil grown plants. The analysis revealed differences in the stress-induced Ca2+ transients between both species, implying species-specific sensitivity for different stress conditions.
However, stress-induced Ca2+ transients occur in each individual cell and the induced changes are specific for certain cells or tissues. To analyse such cell-specific responses, a potato line carrying the fluorescence-based Ca2+ indicator GCaMP3 was generated.
Figure 1: A) ATP induced Ca2+transient observed via changes in GCaMP3 fluorescence. B) Still pictures from three different time points of a video recording of stress-induced Ca2+ waves observed using a fluorescence microscope
The protein GCaMP3 increases its fluorescence in direct correlation to free Ca2+ levels and thus allows visualization of short-term changes in free Ca2+ on a cellular level. The indicator localizes in the cytosol and nucleus and due to the high-resolution of modern fluorescence microscopes, changes in the Ca2+ levels of both compartments can even be analysed separately. In initial tests, changes in GCaMP3 fluorescence in response to external application of ATP (Figure 1A) and stress-induced Ca2+ waves going through the stolon tissue of potato were observed (Figure 1B).
This new sensor line will become part of ADAPT’s ongoing studies on early signaling events in the potato variety Désirée under drought/heat and flooding stress to ultimately generate a detailed timeline and comprehensive event map of early stress responses. Moreover, they will be used to address questions regarding Ca2+ signaling in stolon development and cell specific stress response, e.g. in stomata.
For more information about the project and the latest news, please visit our website at adapt.univie.ac.at or follow us on Twitter @eu_adapt.
