Ancient signals: comparative genomics of green plant CDPKs

• Calcium-dependent protein kinases (CDPKs) are conserved proteins.
• CDPKs combine Ca2+-binding and signaling capabilities.
• We compare CDPKs from angiosperms and early diverging green plant lineages.
• Current architecture of the CDPK family was shaped during land colonization by plants.
• Chlorophyta CDPKs constitute alga-specific phylogenetic groups that apparently kept evolving independently.
• We suggest that the Chloropyhta–Streptophyta split played a key role in CDPK evolution.

Calcium-dependent protein kinases (CDPKs) are multifunctional proteins that combine calcium-binding and signaling capabilities within a single gene product. This unique versatility enables multiple plant biological processes to be controlled, including developmental programs and stress responses. The genome of flowering plants typically encodes around 30 CDPK homologs that cluster in four conserved clades. In this review, we take advantage of the recent availability of genome sequences from green algae and early land plants to examine how well the previously described CDPK family from angiosperms compares to the broader evolutionary states associated with early diverging green plant lineages. Our analysis suggests that the current architecture of the CDPK family was shaped during the colonization of the land by plants, whereas CDPKs from ancestor green algae have continued to evolve independently.