Abstract
The interplay between abscisic acid (ABA) and salicylic acid (SA) influences plant responses to various (a)biotic stresses; however, the underlying mechanism for this crosstalk is largely unknown. Here, we report that type 2C protein phosphatases (PP2Cs), some of which are negative regulators of ABA signaling, bind SA. SA binding suppressed the ABA‐enhanced interaction between these PP2Cs and various ABA receptors belonging to the PYR/PYL/RCAR protein family. Additionally, SA suppressed ABA‐enhanced degradation of PP2Cs and ABA‐induced stabilization of SnRK2s. Supporting SA's role as a negative regulator of ABA signaling, exogenous SA suppressed ABA‐induced gene expression, whereas the SA‐deficient sid2‐1 mutant displayed heightened PP2C degradation and hypersensitivity to ABA‐induced suppression of seed germination. Together, these results suggest a new molecular mechanism through which SA antagonizes ABA signaling. A better understanding of the crosstalk between these hormones is important for improving the sustainability of agriculture in the face of climate change.
Highlights
Elaborate hormone signaling networks allow plants to perceive and respond adaptively to various biotic and abiotic stresses (Tuteja, 2007; Raghavendra et al, 2010)
Recombinant histidine-tagged PP2C-D4 was produced in Escherichia coli and the purified protein was further assessed for salicylic acid (SA)-binding activity using three different assays, including surface plasmon resonance (SPR), photoaffinity crosslinking, and size-exclusion chromatography
SA binding was not detected for two other phosphatases, HAB1 or phosphatase 2A regulatory subunit A (PP2A), or for other components of the abscisic acid (ABA)
Summary
Elaborate hormone signaling networks allow plants to perceive and respond adaptively to various biotic and abiotic stresses (Tuteja, 2007; Raghavendra et al, 2010). One of the vital hormones that plays a central role in the adaptation to abiotic stresses, drought and salt stresses, is ABA. ABA is involved in regulating plant growth and developmental processes under non-stress conditions (Raghavendra et al, 2010) and modulating defense responses following pathogen attack (Robert-Seilaniantz et al, 2011; Denance et al, 2013). Because of its essential role in multiple physiological processes both under stressed and non-stressed conditions, the ABA signaling pathway has been studied intensively during the last two decades. Several proteins were proposed to be ABA receptors, but their exact role in ABA response and their associated mechanisms were never established (Hauser et al, 2011)
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