Calcium-Dependent Protein Kinases in Plants: Evolution, Expression and Function

Abstract

Calcium-dependent protein kinases (CPKs) are plant proteins that directly bind calcium ions before phosphorylating substrates involved in metabolism, osmosis, hormone response and stress signaling pathways. CPKs are a large multigene family of proteins that are present in all plants studied to date, as well as in protists, oomycetes and green algae, but are not found in animals and fungi. Despite the increasing evidence of the importance of CPKs in developmental and stress responses from various plants, a comprehensive genome-wide analysis of CPKs from algae to higher plants has not been undertaken. This paper describes the evolution of CPKs from green algae to plants using a broadly sampled phylogenetic analysis and demonstrates the functional diversification of CPKs based on expression and functional studies in different plant species. Our findings reveal that CPK sequence diversification into four major groups occurred in parallel with the terrestrial transition of plants. Despite significant expansion of the CPK gene family during evolution from green algae to higher plants, there is a high level of sequence conservation among CPKs in all plant species. This sequence conservation results in very little correlation between CPK evolutionary groupings and functional diversity, making the search for CPK functional orthologs a challenge.

Algal ancestor of land plants was preadapted for symbiosis

“…S5) (36). One specific feature of CCaMKs compared with CDPKs is the presence of a calmodulin-binding domain (CBD) overlapping with the autoinhibitory domain (37).…”

Analysis of Noncanonical Calcium-Dependent Protein Kinases in Toxoplasma gondii by Targeted Gene Deletion Using CRISPR/Cas9

“…CDPKs are found in green algae, higher plants, ciliates, and oomycetes, as well as being in apicomplexan parasites (10). Although they are lacking in animal cells, CDPKs are similar in many ways to calcium-calmodulin-dependent kinases (CaMK).…”

“…Upon binding to calcium, the CAD domain completely reorganizes and flips to the backside of the kinase domain, opening the nucleotide and substrate binding pockets to activate the enzyme (11,12). CDPKs likely arose by fusion of a calmodulin-like domain containing four EF hands, a structural feature first described in parvalbumin and that is responsible for calcium binding, followed by their diversification in plants and protists (10). The fact that CDPKs are not found in animal cells, combined with the findings that some of them are essential, has made them attractive targets for development of inhibitors (15).…”

Role of the Plasma Membrane in Saline Conditions: Lipids and Proteins

“…The receptor proteins identified on the PM are known to sense various environmental stimuli and transduce them to downstream intracellular signaling networks (Cheng et al, 2009). It is important to mention that the receptor proteins located on the PM are suggested as potential candidate genes for genetic engineering of improved stress tolerant crops (Osakabe et al, 2013;Valmonte et al, 2014). On the other hand, overexpression of RPK1 proteins (receptor-like protein kinase) distributed in the PM inhibits Arabidopsis salt tolerance (Shi et al, 2014).…”