Calmodulins and Calcineurin B–like Proteins

Luan, Sheng; Kudla, Jörg; Rodríguez‐Concepción, Manuel; Yalovsky, Shaul; Gruissem, Wilhelm

doi:10.1105/tpc.001115

Cited by 609 publications

(129 citation statements)

References 95 publications

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“…Calcineurin B-like (CBL) proteins are a unique family of calcium sensors in plants (14,15). The CBL proteins function by interacting with and regulating a unique family of plant protein kinases (called CIPKs for CBL-interacting protein kinases) (15)(16)(17)(18)(19).…”

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confidence: 99%

A Ca ²⁺ signaling pathway regulates a K ⁺ channel for low-K response in Arabidopsis

Kim

Cheong

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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Nutrient sensing is critical for plant adaptation to the environment. Because of extensive farming and erosion, low content of mineral nutrients such as potassium (K ؉ ) in soils becomes a limiting factor for plant growth. In response to low-K conditions, plants enhance their capability of K ؉ uptake through an unknown signaling mechanism. Here we report the identification of a Ca 2؉ -dependent pathway for low-K response in Arabidopsis. We are not aware of any other example of a molecular pathway for a nutrient response in plants. Earlier genetic analyses revealed three genes encoding two Ca 2؉ sensors (CBL1 and CBL9) and their target protein kinase (CIPK23) to be critical for plant growth on low-K media and for stomatal regulation, indicating that these calcium signaling components participate in the low-K response and turgor regulation. In this study, we show that the protein kinase CIPK23 interacted with, and phosphorylated, a voltage-gated inward K ؉ channel (AKT1) required for K ؉ acquisition in Arabidopsis. In the Xenopus oocyte system, our studies showed that interacting calcium sensors (CBL1 and CBL9) together with target kinase CIPK23, but not either component alone, activated the AKT1 channel in a Ca 2؉ -dependent manner, connecting the Ca 2؉ signal to enhanced K ؉ uptake through activation of a K ؉ channel. Disruption of both CBL1 and CBL9 or CIPK23 gene in Arabidopsis reduced the AKT1 activity in the mutant roots, confirming that the Ca 2؉ -CBL-CIPK pathway functions to orchestrate transporting activities in planta according to external K ؉ availability.calcium signaling ͉ potassium channel ͉ nutrient sensing ͉ potassium uptake ͉ protein kinase P lants and microbes are able to adapt to widely varying environmental conditions, including the availability of inorganic nutrients. The response to K ϩ is especially relevant because it is the major inorganic osmoticum that contributes to turgor pressure and, hence, to cellular growth and development (1, 2). Both plants and fungi maintain internal K ϩ near 100 mM even when extracellular K ϩ varies between 1 M and 100 mM (i.e., over five orders of magnitude in free concentration). A large collection of transporters is required for this homeostatic mechanism (3-6), yet little is known about the mechanism underlying regulation and integration of the transport activities in concert with the extracellular K ϩ levels. Some studies suggest that plants enhance their capability of K ϩ uptake by activating some K ϩ transporters in response to K ϩ -deficient conditions (7-10). A signaling process exists for the plants to ''monitor'' external K ϩ concentration and ''respond'' to the low-K condition by enhancing the capability for K ϩ acquisition. This signaling pathway represents a typical nutrient sensing and response process in plants about which our knowledge is extremely limited. One recent study indicates that low-K status in the soil triggers elevated production of H 2 O 2 that may serve as a signaling molecule to alter the expression of certain genes (11). Becaus...

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confidence: 99%

A Ca ²⁺ signaling pathway regulates a K ⁺ channel for low-K response in Arabidopsis

Kim

Cheong

et al. 2006

Proc. Natl. Acad. Sci. U.S.A.

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403

303

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“…In plants one of the earliest cellular responses to external stimuli is a transient increase in cytosolic Ca 2ϩ concentration (1)(2)(3)(4) and the subsequent propagation of this signal through the binding of Ca 2ϩ to various Ca 2ϩ -sensing proteins, such as calmodulin (CaM), 5 calcineurin B-like protein, and calciumdependent protein kinase (5)(6)(7)(8). CaM is known to couple Ca 2ϩ signals to changes in the activity of downstream target proteins via direct interaction.…”

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confidence: 99%

Identification of a Calmodulin-binding NAC Protein as a Transcriptional Repressor in Arabidopsis

Kim

Park²,

Yoo

et al. 2007

Journal of Biological Chemistry

119

111

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“…One might speculate that this is because of the different requirements of both molecules; CaM is required to interact with numerous cellular targets (33), whereas each CLD is tailored to interact intramolecularly with its own target. As a result, physiologically, the Ca 2ϩ form of CLD likely exists only very briefly and sets the stage for the more physiologically relevant JD-bound state, hence the interdomain associations observed by FRET and NMR.…”

Section: Discussionmentioning

confidence: 99%

Conformational Changes in the Ca2+-regulatory Region from Soybean Calcium-dependent Protein Kinase-α

Weljie¹,

Robertson

Vogel

2003

Journal of Biological Chemistry

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Calcium-dependent protein kinases are key proteins involved in plant and protozoal Ca 2؉ signaling. These unique molecules include a calcium regulatory calmodulin-like domain (CLD), which binds to another small regulatory domain named the junction domain (JD). Both CLD and JD are part of the same polypeptide as the protein kinase domain. The CLD consists of N-and C-terminal lobes, each having two helix-loop-helix Ca 2؉ -binding motifs. In this study, fluorescence resonance energy transfer using a series of Trp and Cys site-directed mutants was undertaken to probe the relative motions of the two lobes of CLD between the apo-and Ca 2؉ -saturated forms, as well as bound to a peptide encoding the JD sequence. Using an IAEDANS-modified Cys, a total of 15 Trp 3 Cys distances were measured in these three states from the five donor-acceptor combinations F334W-Cys 436 , L371W-Cys 436 , L403W-Cys 436 , F334W-L403C, and L371W-L403C. Consistent with recently reported NMR diffusion measurements and with 1 H, 15 N heteronuclear correlation NMR spectra, the distances derived from fluorescence resonance energy transfer measurements in apoCLD indicate partial unfolding and a subsequent contraction on binding Ca 2؉ , which is maintained on addition of the JD peptide. Interpretation of the distances suggests that the Ca 2؉ -saturated form is open with the two lobes sitting side-by-side although highly flexible. The transition to the JD-CLD state appears to be accompanied by a rotation of the N-and C-terminal domains with respect to each other inducing a slightly more closed overall complex. The observed differences between the behavior of CLD and the well studied related protein calmodulin are likely because of different physiological requirements for activation in vivo.Calcium-dependent protein kinases (CDPKs) 1 play a crucial role in the Ca 2ϩ -induced signaling pathways of both plants and protists (1-3). The CDPK response is calcium-dependent but calmodulin (CaM)-independent, presumably because of the presence of an internal Ca 2ϩ -regulatory region (calmodulinlike domain, or CLD) near the C terminus of CDPK. The CLD is very similar (Ͼ40% identity) to the ubiquitous calcium-regulatory protein CaM. The target for the CLD is another short domain found in CDPK entitled the junction domain (JD), which connects the CLD with the N-terminal protein kinase domain (4, 5).In vivo, increases in the cytosolic [Ca 2ϩ ] presumably are thought to induce a structural change directly from the apo state of the CLD to the activated (JD-CLD) form. Bimolecular studies (2, 6, 7) demonstrate that significant activity can be reconstituted using truncated CDPK constructs lacking the CLD with exogenous CLD in the presence of Ca 2ϩ . Although recent structural work demonstrates that the CLD shares the same global fold as CaM, it is clear that functionally (2, 6, 7) and structurally there are also some significant distinctions. 2 Like CaM (8 -10), CLD is comprised of two domains, each consisting of two helix-loop-helix EF-hand Ca 2ϩ binding loops (see Fi...

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Calmodulins and Calcineurin B–like Proteins

Cited by 609 publications

References 95 publications

A Ca ²⁺ signaling pathway regulates a K ⁺ channel for low-K response in Arabidopsis

A Ca ²⁺ signaling pathway regulates a K ⁺ channel for low-K response in Arabidopsis

Identification of a Calmodulin-binding NAC Protein as a Transcriptional Repressor in Arabidopsis

Conformational Changes in the Ca2+-regulatory Region from Soybean Calcium-dependent Protein Kinase-α

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Calmodulins and Calcineurin B–like Proteins

Cited by 609 publications

References 95 publications

A Ca 2+ signaling pathway regulates a K + channel for low-K response in Arabidopsis

A Ca 2+ signaling pathway regulates a K + channel for low-K response in Arabidopsis

Identification of a Calmodulin-binding NAC Protein as a Transcriptional Repressor in Arabidopsis

Conformational Changes in the Ca2+-regulatory Region from Soybean Calcium-dependent Protein Kinase-α

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A Ca ²⁺ signaling pathway regulates a K ⁺ channel for low-K response in Arabidopsis

A Ca ²⁺ signaling pathway regulates a K ⁺ channel for low-K response in Arabidopsis