Identification and comparative analysis of the gene family and characterization of the cold stress response in the woody plant .

is an important ornamental woody plant that grows in tropical and subtropical regions. Freezing stress can adversely impact plant productivity and limit the expansion of geographical locations. Understanding cold-responsive genes could potentially bring about the development of new ways to enhance plant freezing tolerance. Members of the serine/threonine protein kinase () gene family play important roles in abiotic stress. However, the function of genes in remains poorly defined. A total of 16 genes were first identified in . A systematic phylogenetic analysis was conducted in which 253 genes from 12 species were divided into three groups. Furthermore, we analysed the chromosomal locations, molecular structures, motifs and domains of genes in . All of the CIPK sequences had NAF domains and promoter regions containing cis-acting regulatory elements of the related stress response. Three genes were identified as Pmu-miR172/167-targeted sites. Transcriptome data showed that most genes presented tissue-specific and time-specific expression profiles. Nine genes were highly expressed in flower buds in December and January, and 12 genes were up-regulated in stems in winter. The expression levels of 12 genes were up-regulated during cold stress treatment confirmed by qRT-PCR. Our study improves understanding of the role of the gene family in the low temperature response in woody plants and provides key candidate genes and a theoretical basis for cold resistance molecular-assisted breeding technology in .