Genome-Wide Identification, Characterization and Expression Profiles of Calcium-Dependent Protein Kinase Genes in Barley (Hordeum vulgare L.)

Calcium-dependent protein kinases (CDPKs) acting in plant cells are important sensors of Ca²⁺ flux resulting from various environmental stresses like cold, drought or salt stress. Previous genome sequence analysis and comparative studies in Arabidopsis (Arabidopsis thaliana L.) and rice (Oryza sativa L.) allowed to define a multigene family of CDPKs. Here, we identified and characterized the CDPK gene complement of the model cereal, barley (Hordeum vulgare L.). Comparative analysis encompassed phylogeny reconstruction based on newly available barley genome sequence, as well as established model genomes (e.g. O. sativa, A. thaliana, Brachypodium distachyon). Functional gene copies possessed characteristic CDPK domain architecture, including a serine-threonine kinase domain and four regulatory EF-hand motifs. In silico verification was followed by measurements of transcript abundance via Real-Time PCR. The relative expression of CDPK genes was determined in the vegetative growth stage under intensifying drought stress conditions. The majority of barley CDPK genes showed distinct changes in patterns of expression during exposure to stress. Our study underscores the involvement of the barley CDPK gene complement in drought adaptation and the need for a coordinated systems biology approach to unravel the roles of differentially expressed genes that regulate physiological processes.