TY  - JOUR
A1  - Li, Kunkun
A1  - Prada, Juan
A1  - Damineli, Daniel S. C.
A1  - Liese, Anja
A1  - Romeis, Tina
A1  - Dandekar, Thomas
A1  - Feijó, José A.
A1  - Hedrich, Rainer
A1  - Konrad, Kai Robert
T1  - An optimized genetically encoded dual reporter for simultaneous ratio imaging of Ca\(^{2+}\) and H\(^{+}\) reveals new insights into ion signaling in plants
JF  - New Phytologist
N2  - Whereas the role of calcium ions (Ca\(^{2+}\)) in plant signaling is well studied, the physiological significance of pH‐changes remains largely undefined.

Here we developed CapHensor, an optimized dual‐reporter for simultaneous Ca\(^{2+}\) and pH ratio‐imaging and studied signaling events in pollen tubes (PTs), guard cells (GCs), and mesophyll cells (MCs). Monitoring spatio‐temporal relationships between membrane voltage, Ca\(^{2+}\)‐ and pH‐dynamics revealed interconnections previously not described.

In tobacco PTs, we demonstrated Ca\(^{2+}\)‐dynamics lag behind pH‐dynamics during oscillatory growth, and pH correlates more with growth than Ca\(^{2+}\). In GCs, we demonstrated abscisic acid (ABA) to initiate stomatal closure via rapid cytosolic alkalization followed by Ca2+ elevation. Preventing the alkalization blocked GC ABA‐responses and even opened stomata in the presence of ABA, disclosing an important pH‐dependent GC signaling node. In MCs, a flg22‐induced membrane depolarization preceded Ca2+‐increases and cytosolic acidification by c. 2 min, suggesting a Ca\(^{2+}\)/pH‐independent early pathogen signaling step. Imaging Ca2+ and pH resolved similar cytosol and nuclear signals and demonstrated flg22, but not ABA and hydrogen peroxide to initiate rapid membrane voltage‐, Ca\(^{2+}\)‐ and pH‐responses.

We propose close interrelation in Ca\(^{2+}\)‐ and pH‐signaling that is cell type‐ and stimulus‐specific and the pH having crucial roles in regulating PT growth and stomata movement.
KW  - abscisic acid (ABA)
KW  - calcium
KW  - flg22
KW  - guard cells
KW  - imaging
KW  - ion signaling
KW  - pH
KW  - pollen tube
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-239847
VL  - 230
IS  - 6
SP  - 2292
EP  - 2310
ER  - 
TY  - JOUR
A1  - Lehmann, Julian
A1  - Jørgensen, Morten E.
A1  - Fratz, Stefanie
A1  - Müller, Heike M.
A1  - Kusch, Jana
A1  - Scherzer, Sönke
A1  - Navarro-Retamal, Carlos
A1  - Mayer, Dominik
A1  - Böhm, Jennifer
A1  - Konrad, Kai R.
A1  - Terpitz, Ulrich
A1  - Dreyer, Ingo
A1  - Mueller, Thomas D.
A1  - Sauer, Markus
A1  - Hedrich, Rainer
A1  - Geiger, Dietmar
A1  - Maierhofer, Tobias
T1  - Acidosis-induced activation of anion channel SLAH3 in the flooding-related stress response of Arabidopsis
JF  - Current Biology
N2  - Plants, as sessile organisms, gained the ability to sense and respond to biotic and abiotic stressors to survive severe changes in their environments. The change in our climate comes with extreme dry periods but also episodes of flooding. The latter stress condition causes anaerobiosis-triggered cytosolic acidosis and impairs plant function. The molecular mechanism that enables plant cells to sense acidity and convey this signal via membrane depolarization was previously unknown. Here, we show that acidosis-induced anion efflux from Arabidopsis (Arabidopsis thaliana) roots is dependent on the S-type anion channel AtSLAH3. Heterologous expression of SLAH3 in Xenopus oocytes revealed that the anion channel is directly activated by a small, physiological drop in cytosolic pH. Acidosis-triggered activation of SLAH3 is mediated by protonation of histidine 330 and 454. Super-resolution microscopy analysis showed that the increase in cellular proton concentration switches SLAH3 from an electrically silent channel dimer into its active monomeric form. Our results show that, upon acidification, protons directly switch SLAH3 to its open configuration, bypassing kinase-dependent activation. Moreover, under flooding conditions, the stress response of Arabidopsis wild-type (WT) plants was significantly higher compared to SLAH3 loss-of-function mutants. Our genetic evidence of SLAH3 pH sensor function may guide the development of crop varieties with improved stress tolerance.
KW  - SLAH3
KW  - S-type anion channel
KW  - hypoxia
KW  - pH
KW  - cytosolic acidification
KW  - flooding
KW  - PALM
KW  - stoichiometry
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-363320
VL  - 31
ER  -