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Elife. 2015 Jul 20;4. doi: 10.7554/eLife.03599.

Calcium specificity signaling mechanisms in abscisic acid signal transduction in Arabidopsis guard cells.

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Division of Biological Sciences, Cell and Developmental Biology Section, University of California, San Diego, San Diego, United States.


A central question is how specificity in cellular responses to the eukaryotic second messenger Ca(2+) is achieved. Plant guard cells, that form stomatal pores for gas exchange, provide a powerful system for in depth investigation of Ca(2+)-signaling specificity in plants. In intact guard cells, abscisic acid (ABA) enhances (primes) the Ca(2+)-sensitivity of downstream signaling events that result in activation of S-type anion channels during stomatal closure, providing a specificity mechanism in Ca(2+)-signaling. However, the underlying genetic and biochemical mechanisms remain unknown. Here we show impairment of ABA signal transduction in stomata of calcium-dependent protein kinase quadruple mutant plants. Interestingly, protein phosphatase 2Cs prevent non-specific Ca(2+)-signaling. Moreover, we demonstrate an unexpected interdependence of the Ca(2+)-dependent and Ca(2+)-independent ABA-signaling branches and the in planta requirement of simultaneous phosphorylation at two key phosphorylation sites in SLAC1. We identify novel mechanisms ensuring specificity and robustness within stomatal Ca(2+)-signaling on a cellular, genetic, and biochemical level.


SLAC1; SnRK; abscisic acid (ABA); arabidopsis; calcium specificity; calcium-dependent protein kinase (CPK); plant biology; protein phosphatase 2C (PP2C)

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