https://orcid.org/0000-0002-4259-8296
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Magdalena Julkowska, A Tale of Two Isoforms: Calcium-Dependent Inhibition of SnRK2 by SnRK-Calcium-Binding Sensor, Plant Physiology, Volume 182, Issue 2, February 2020, Pages 683–684, https://doi.org/10.1104/pp.19.01554
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Reacting to the environment requires not only activating signaling cascades but also modulating the activity of individual components in a context- and time-dependent manner. For example, under nonstress conditions, protein phosphatases 2C (PP2C) keep the SnRK2 abscisic acid (ABA)-dependent protein kinases in an inactive state (Dupeux et al., 2011). Upon exposure to stress, ABA activates the PYR/PYL receptors, which interact with the PP2Cs (Park et al., 2009), releasing the SnRK2 protein kinases (Fig. 1). ABA-dependent SnRK2s have important functions in regulating stomatal closure and growth (Fujii and Zhu, 2009), but their activity is only transient (Boudsocq et al., 2007; McLoughlin et al., 2012). SnRKs interact with other proteins that modify their activities, including calcium-binding proteins. Previously, Bucholc et al. (2011) screened for proteins interacting with osmotic stress-activated protein kinase, a member of the SnRK2 family in Nicotiana tabacum. One of the SnRK2 interactors identified is a calcium-binding protein they named SnRK-Calcium-binding Sensor (SCS), which inhibits SnRK2 kinase activity upon Ca2+ binding (Bucholc et al., 2011). SCS was established to play a role in seed germination, but the nature of the interaction between SnRK2 and SCS, and its significance for other ABA-dependent processes, were unknown.
