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An optimized genetically encoded dual reporter for simultaneous ratio imaging of Ca 2+ and H + reveals new insights into ion signaling in plants
Author(s) -
Li Kunkun,
Prada Juan,
Damineli Daniel S. C.,
Liese Anja,
Romeis Tina,
Dandekar Thomas,
Feijó José A.,
Hedrich Rainer,
Konrad Kai Robert
Publication year - 2021
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/nph.17202
Subject(s) - guard cell , cytosol , abscisic acid , biophysics , second messenger system , calcium signaling , microbiology and biotechnology , calcium , membrane , chemistry , biochemistry , signal transduction , biology , enzyme , gene , organic chemistry
Summary 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 Ca 2+ 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 Ca 2+ ‐increases and cytosolic acidification by c.  2 min, suggesting a Ca 2+ /pH‐independent early pathogen signaling step. Imaging Ca 2+ 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.

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