Genome-wide survey indicates diverse physiological roles of the barley (Hordeum vulgare L.) calcium-dependent protein kinase genes

Calcium-dependent protein kinases (CDPKs) are crucial calcium sensors that play important roles in the regulation of plant growth and developmental processes, as well as protective responses to environmental stress. Here, we identified 28 CDPK genes from barley and cloned 5 new, full-length CDPK genes, MLOC_58648a, MLOC_19618a, MLOC_71733a, AK249361a and MLOC_4965a, using their expressed sequence tags. Phylogenetic and gene structural analyses revealed that the CDPK could be divided into four subgroups. Significant site-specific altered constraints and a high evolutionary rate may have contributed to the functional divergences among CDPK gene subfamilies. Expression profiles of different tissues and developmental stages suggested that several CDPK genes are involved in the functional development of plants. Different expression levels under a variety of abiotic stresses also indicated that the CDPK family underwent functional divergence during long-term evolution. Furthermore, several CDPK genes responded to single treatments and individual CDPK genes responded to multiple treatments, suggesting that barley CDPKs may be involved in mediating cross-talk among different signalling pathways. Our data provide an important foundation for the functional and evolutionary analyses of this important gene family in barley.