DECODING Ca²⁺ SIGNALS THROUGH PLANT PROTEIN KINASES

Abstract

Plants harbor four families of kinases that have been implicated in Ca(2+) signaling (CDPKs, CRKs, CCaMKs, and SnRK3s). Although each family appears to respond to Ca(2+) via different mechanisms, they all utilize Ca(2+) sensors that bind Ca(2+) through multiple EF-hands. The CDPK (Ca(2+)-dependent protein kinase) family is represented by the most genes, with 12 subfamilies comprised of 34 isoforms in Arabidopsis and 27 in rice. Some of the calcium-regulated kinases also show potential for regulation by lipid signals and kinase cascades. Thus, Ca(2+)-regulated kinases provide potential nodes of cross-talk for multiple signaling pathways that integrate Ca(2+) signals into all aspects of plant growth and development.

Inactivation of Plasma Membrane–Localized CDPK-RELATED KINASE5 Decelerates PIN2 Exocytosis and Root Gravitropic Response inArabidopsis

“…Nonetheless, specific roles of CRKs in the control of root gravitropism remained thus far hidden because the available inhibitors and agonists could target more than one classes of signaling factors. The CaM antagonist KM-93 might thus interfere with the activities of CCaMK Ca 2+ and calmodulin-activated kinases, which carry visinin-like C-terminal Ca 2+ binding motives (Zhang and Lu, 2003), in addition to inhibiting CRKs that harbor defective Ca 2+ binding EF-hand motives, and are thus active also in the absence of Ca 2+ (Harper et al, 2004). Unlike some other plant species, intriguingly, no genuine CCaMK kinase is encoded by the Arabidopsis genome .…”

“…CRK5 is one of the eight members of the Arabidopsis CRK family, which share very similar structural and biochemical features with CRKs characterized in other plant species (Harper et al, 2004). N-terminal sequences of CRKs show high variability, except for two conserved domains corresponding to an MGxC myristoylation and palmitoylation motif and a downstream putative nuclear localization signal, which are also present in CRK5 (see Supplemental Figure 3 online).…”

“…Here, we show that CRK5, a member of the Arabidopsis thaliana Ca 2+ /calmodulin-dependent kinase-related (CRK) protein family (Harper et al, 2004), is required for proper polar localization of PIN2 in the transition zones of roots. Inactivation of CRK5 causes a root gravitropic defect and stimulates lateral root formation.…”

Nuclear-Localized and Deregulated Calcium- and Calmodulin-Dependent Protein Kinase Activates Rhizobial and Mycorrhizal Responses in Lotus japonicus

“…The deregulation of symbiosis signaling by the truncated CCaMK protein emphasizes the negative regulatory role of the C-terminal domains, that is, the CaM BD and the three EF hands (Gleason et al, 2006). The C-terminal domains have been reported to possess an autoinhibitory activity through their ability to change conformation (Sathyanarayanan et al, 2000;Harper et al, 2004). In the inactive form, the folded C-terminal region covers the kinase domain.…”

Induction of anthraquinone biosynthesis in Rubia cordifolia cells by heterologous expression of a calcium‐dependent protein kinase gene

“…2011;108: 1734-1738. ß 2011 Wiley Periodicals, Inc. KEYWORDS: calcium-dependent protein kinase; Rubia cordifolia; anthraquinones; isochorismate synthase; callus culture; metabolic engineering Calcium-dependent protein kinases (CDPKs) represent a class of a multigene family that is ubiquitous in the plant kingdom and serves as one of the components in a complex calcium decoding system (Harper et al, 2004). CDPKs participate in the regulation of a variety of cell functions, and play an important role in biotic and abiotic plant stress responses (reviewed in Cheng et al, 2002;Ludwig et al, 2004).…”