Genome-Wide Identification of CIPK Genes in Sugar Beet (Beta vulgaris) and Their Expression Under NaCl Stress

Salinity is one of the major abiotic factors that limits the growth and development of plants and the productivity of crops worldwide. Calcineurin B-like protein (CBL)-interacting protein kinases (CIPKs) have been shown to play a vital role in response to salt stress in plants. Although CIPKs have been widely identified in various species, the genome-wide identification of CIPKs and their expression patterns in sugar beet (Beta vulgaris L.) are unclear. In the present study, a total of 20 BvCIPK genes were identified in the genome of sugar beet and classified into five major groups A-E based on the phylogenetic analysis, and the classification was supported by the intron/exon structures and the distribution of conserved motifs. The NAF (Asn-Ala-Phe)/FISL (Phe-Ile-Ser-Leu) and protein-phosphatase interaction (PPI) domains were found on the C-terminus of BvCIPKs. The 19 BvCIPK genes were unevenly distributed onto seven chromosomes of sugar beet, and one gene was mapped onto unassembled scaffold based on the current genome database. Furthermore, the majority of BvCIPKs were significantly up-regulated by 50 and 100 mM NaCl. Notably, the expression levels of BvCIPK15 in shoots under two levels of NaCl were 7.4- and 4.7-fold higher than those under control condition, respectively. These results implied that BvCIPKs might be involved in the salt response of sugar beet. The findings of present study may provide new insights into the further molecular dissection of biological functions for salt tolerance in sugar crops.