Comparative genomic analysis of the CPK gene family in Moso bamboo (Phyllostachys edulis) and the functions of PheCPK1 in drought stress

Calcium-dependent protein kinases (CPKs) play an important role in plant regulation of growth and development, and in the responses to biotic and abiotic stresses. In the present study, we analyzed Moso bamboo (Phyllostachys edulis) CPK genes and their closely related five gene families (Brachypodium distachyon, Hordeum vulgare L., Oryza sativa, Setaria italica, and Zea mays) comprehensively, including phylogenetic relationships, gene structures, and synteny analysis. Thirty Moso bamboo CPKs were divided into four subgroups; in each subgroup, the constituent parts of gene structure were relatively conserved. Furthermore, analysis of expression profiles showed that most PheCPK genes are significantly upregulated under drought and cold stress, especially PheCPK1. Overexpression of PheCPK1 in Arabidopsis reduced plant tolerance to drought stress, as determined through physiological analyses of the relative water content, relative electrical leakage, and malondialdehyde content. It also activated the expressions of stress-related genes. In addition, overexpression of PheCPK1 in Arabidopsis exhibited significantly decreased reactive oxygen species (ROS)-scavenging ability. Taken together, these results suggest that PheCPK1 may act as a negative regulator involved in the drought stress responses.