The Arabidopsis Chaperone J3 Regulates the Plasma Membrane H+-ATPase through Interaction with the PKS5 Kinase  

Abstract

The plasma membrane H + -ATPase (PM H + -ATPase) plays an important role in the regulation of ion and metabolite transport and is involved in physiological processes that include cell growth, intracellular pH, and stomatal regulation. PM H + -ATPase activity is controlled by many factors, including hormones, calcium, light, and environmental stresses like increased soil salinity. We have previously shown that the Arabidopsis thaliana Salt Overly Sensitive2-Like Protein Kinase5 (PKS5) negatively regulates the PM H + -ATPase. Here, we report that a chaperone, J3 (DnaJ homolog 3; heat shock protein 40-like), activates PM H + -ATPase activity by physically interacting with and repressing PKS5 kinase activity. Plants lacking J3 are hypersensitive to salt at high external pH and exhibit decreased PM H + -ATPase activity. J3 functions upstream of PKS5 as double mutants generated using j3-1 and several pks5 mutant alleles with altered kinase activity have levels of PM H + -ATPase activity and responses to salt at alkaline pH similar to their corresponding pks5 mutant. Taken together, our results demonstrate that regulation of PM H + -ATPase activity by J3 takes place via inactivation of the PKS5 kinase.

The Tomato Calcium Sensor Cbl10 and Its Interacting Protein Kinase Cipk6 Define a Signaling Pathway in Plant Immunity

“…CBLs and CIPKs have been described to interact specifically with protein phosphatases, the chaperone-like protein DNAJ and a 14-3-3 protein (Fuglsang et al, 2007;Yang et al, 2010). Understanding the regulation of the formation of the Cbl10/Cipk6 complex, identification of additional regulatory components, together with transcriptional regulation of their genes under developmental-, tissue-, and cell-specific and environmental or biotic stress conditions will be important for understanding how downstream Cbl10/Cipk6 signaling specificity is achieved from upstream Ca 2+ -derived signals in abiotic and biotic stress signaling.…”

An Arabidopsis Plasma Membrane Proton ATPase Modulates JA Signaling and Is Exploited by the Pseudomonas syringae Effector Protein AvrB for Stomatal Invasion

“…Plasma membrane vesicles were isolated using aqueous twophase partitioning and the H + -ATPase activity assay was performed as described previously (Yang et al, 2010).…”

Phosphorylation of SOS3-Like Calcium-Binding Proteins by Their Interacting SOS2-Like Protein Kinases Is a Common Regulatory Mechanism in Arabidopsis

“…To determine if this phosphorylation regulation occurs in other functional interacting SCaBP-PKS pairs, in vitro kinase assays were performed between SCaBP1 and PKS5 (Fuglsang et al, 2007;Yang et al, 2010), CBL1/SCaBP5 or CBL9/ SCaBP7 and CIPK23/PKS17 (Xu et al, 2006), and SCaBP1 and PKS24 (Akaboshi et al, 2008). PKS24, CIPK23, CBL1, and CBL9 cDNA was fused to a GST gene.…”

“…The CBL1-and CBL9-CIPK23 complexes phosphorylate and regulate AKT1 to protect plants from low potassium stress (Xu et al, 2006). SCaBP1 action is required for PKS5 to phosphorylate and negatively regulate AHA2 to mediate the cytoplasmic pH homeostasis (Fuglsang et al, 2007;Yang et al, 2010). In addition to regulating ion transporter activity, PKS kinases have been found to interact with protein phosphatases Ohta et al, 2003;Lee et al, 2007), however the regulatory mechanism is not well understood.…”