The Arabidopsis GORK K+-channel is phosphorylated by calcium-dependent protein kinase 21 (CPK21), which in turn is activated by 14-3-3 proteins

Properties and functions of calcium‐dependent protein kinases and their relatives inArabidopsis thaliana

“…Importantly, 14‐3‐3 interactions observed in vitro have been confirmed in vivo for AtCPK1 and AtCPK3, suggesting relevant biological functions (Camoni et al ., ; Chang et al ., ; Lachaud et al ., ; van Kleeff et al ., ). 14‐3‐3 proteins were shown to stimulate the activity of AtCPK1/21/23 in vitro without affecting calcium sensitivity (Camoni et al ., ; van Kleeff et al ., ) and to prevent AtCPK3 degradation in vivo (Lachaud et al ., ). A more complex interplay between CDPKs and 14‐3‐3 proteins probably occurs as 14‐3‐3 proteins can also be substrates of CDPKs (Swatek et al ., ; Ormancey et al ., ).…”

“…In a large-scale analysis of 759 protein kinases, tyrosine autophosphorylation has been detected on AtCRK2/3/8 while no significant signal over the background could be observed for 17 tested CDPKs (Nemoto et al, 2015). Indeed, very few CPKs could autophosphorylate on Tyr in vitro, including AtCPK28 which is closer to CRKs than to other CDPK subgroups, suggesting that CRKs and subgroup IV CDPKs could share this specific ability (Oh et al, 2012;Swatek et al, 2014;Nemoto et al, 2015;Bender et al, 2017;van Kleeff et al, 2018). Nevertheless, the molecular basis of such activity remains elusive as none of the established tyrosine kinase consensus motifs is present in CDPKs or CRKs (Rudrabhatla et al, 2006).…”

“…Nonetheless, the molecular mechanism of lipid regulation remains elusive with the lack of any known lipid binding domain in CDPKs, despite the direct PA or PC binding observed in vitro for ZmCPK11 and CaCDPK1 (Klimecka et al, 2011;Dixit & Jayabaskaran, 2012). Similarly with 14-3-3 proteins that bind phosphomotifs, no 14-3-3 binding domain has been validated so far in any CDPK, although consensus motifs with autophosphorylation sites were detected in AtCPK1 and AtCPK21 (Camoni et al, 1998;Hegeman et al, 2006;van Kleeff et al, 2018). Importantly, 14-3-3 interactions observed in vitro have been confirmed in vivo for AtCPK1 and AtCPK3, suggesting relevant biological functions (Camoni et al, 1998;Chang et al, 2009;Lachaud et al, 2013;van Kleeff et al, 2014).…”

“…In addition, CPKs also regulate K + channels, either the gated outwardly rectifying K + channel GORK involved in stomatal closure or the inward K + channel KAT1/2 involved in stomatal opening (Ronzier et al, 2014;Corratg e-Faillie et al, 2017;van Kleeff et al, 2018). In particular, cpk10 and cpk8 showed decreased ABA sensitivity for both stomatal closure and inhibition of the K +inward current, which probably contributed to their droughthypersensitive phenotype (Zou et al, 2010(Zou et al, , 2015.…”

Abscisic acid dynamics, signaling, and functions in plants

“…In addition to the modulation of anion channel efflux, other ion channels can be regulated in a Ca 2+ dependent manner. GOAK, a K + outward rectifying channel, is phosphorylated and activated by CPK21 (Hosy et al 2003; van Kleeff et al 2018). Moreover, CPK13 also inactivates KAT1 and KAT2, two K + influx channels, and affects stomatal behavior through specific phosphorylation events (Ronzier et al 2014).…”