Characterization of Arabidopsis calcium-dependent protein kinases: activated or not by calcium?

CDPKs (calcium-dependent protein kinases), which contain both calmodulin-like calcium binding and serine/threonine protein kinase domains, are only present in plants and some protozoans. Upon activation by a stimulus, they transduce the signal through phosphorylation cascades to induce downstream responses, including transcriptional regulation. To understand the functional specificities of CDPKs, 14 Arabidopsis CPKs (CDPKs in plants) representative of the three main subgroups were characterized at the biochemical level, using HA (haemagglutinin)-tagged CPKs expressed in planta. Most of them were partially or mainly associated with membranes, in agreement with acylation predictions. Importantly, CPKs displayed highly variable calcium-dependences for their kinase activities: seven CPKs from subgroups 1 and 2 were clearly sensitive to calcium with different intensities, whereas six CPKs from subgroup 3 exhibited low or no calcium sensitivity to two generic substrates. Interestingly, this apparent calcium-independence correlated with significant alterations in the predicted EF-hands of these kinases, although they all bound calcium. The noticeable exception, CPK25, was calcium-independent owing to the absence of functional EF-hands. Taken together, the results of the present study suggest that calcium binding differentially affects CDPK isoforms that may be activated by distinct molecular mechanisms.

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Molecular Players of EF-hand Containing Calcium Signaling Event in Plants

International Journal of Molecular Sciences ◽

10.3390/ijms20061476 ◽

2019 ◽

Vol 20 (6) ◽

pp. 1476 ◽

Cited By ~ 9

Author(s):

Tapan Mohanta ◽

Dhananjay Yadav ◽

Abdul Khan ◽

Abeer Hashem ◽

Elsayed Abd_Allah ◽

...

Keyword(s):

Calcium Signaling ◽

Protein Kinases ◽

Calcium Binding ◽

Life Forms ◽

Terrestrial Environment ◽

Calcium Dependent ◽

Ef Hand ◽

Dependent Protein ◽

Calcium Dependent Protein Kinases ◽

Ef Hands

Ca2+ is a universal second messenger that plays a pivotal role in diverse signaling mechanisms in almost all life forms. Since the evolution of life from an aquatic to a terrestrial environment, Ca2+ signaling systems have expanded and diversified enormously. Although there are several Ca2+ sensing molecules found in a cell, EF-hand containing proteins play a principal role in calcium signaling event in plants. The major EF-hand containing proteins are calmodulins (CaMs), calmodulin like proteins (CMLs), calcineurin B-like (CBL) and calcium dependent protein kinases (CDPKs/CPKs). CaMs and CPKs contain calcium binding conserved D-x-D motifs in their EF-hands (one motif in each EF-hand) whereas CMLs contain a D-x3-D motif in the first and second EF-hands that bind the calcium ion. Calcium signaling proteins form a complex interactome network with their target proteins. The CMLs are the most primitive calcium binding proteins. During the course of evolution, CMLs are evolved into CaMs and subsequently the CaMs appear to have merged with protein kinase molecules to give rise to calcium dependent protein kinases with distinct and multiple new functions. Ca2+ signaling molecules have evolved in a lineage specific manner with several of the calcium signaling genes being lost in the monocot lineage.

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Antioxidant Response and Calcium-Dependent Protein Kinases Involvement in Canola (Brassica napus L.) Tolerance to Drought

Agronomy ◽

10.3390/agronomy12010125 ◽

2022 ◽

Vol 12 (1) ◽

pp. 125

Author(s):

Hossein Ahmadi ◽

Alireza Abbasi ◽

Alireza Taleei ◽

Valiollah Mohammadi ◽

José J. Pueyo

Keyword(s):

Protein Kinases ◽

Water Deficit ◽

Molecular Mechanisms ◽

Antioxidant Response ◽

Guaiacol Peroxidase ◽

Brassica Napus L ◽

Calcium Dependent ◽

Drought Tolerant ◽

Dependent Protein ◽

Calcium Dependent Protein Kinases

Canola is an important temperate oil crop that can be severely affected by drought. Understanding the physiological and molecular mechanisms involved in canola tolerance to water deficit is essential to obtain drought-tolerant productive cultivars. To investigate the role of antioxidant response and the possible involvement of calcium-dependent protein kinases (CDPKs) in canola tolerance to drought, we analyzed four genotypes with different sensitivity to water stress. Leaf relative water content, canopy temperature, PSII efficiency, electrolyte leakage index and lipid peroxidation were used as indicators to classify the cultivars as drought-tolerant or drought-sensitive. Antioxidant enzymes superoxide dismutase, guaiacol peroxidase and catalase displayed significantly higher activities in drought-tolerant than in drought-sensitive cultivars subjected to water deficit, suggesting that the efficiency of the antioxidant response is essential in canola drought tolerance. The increased expression of genes BnaCDPK6 and BnaCDPK14 under drought conditions, their differential expression in drought-tolerant and drought-sensitive genotypes, and the presence of multiple cis-acting stress-related elements in their promoter regions suggest that CDPKs are part of the signaling pathways that regulate drought response in canola. We propose the BnaCDPK genes and their regulator elements as potential molecular targets to obtain drought-tolerant productive canola cultivars through breeding or genetic transformation.

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