Genome-Wide Identification and Abiotic-Stress-Responsive Expression of Gene Family in

is a tree species of the family, an ancient relict plant mainly used for landscaping and timber production due to its excellent material properties and ornamental value. The cytokinin oxidase/dehydrogenase (CKX) enzyme regulates cytokinin levels and plays an important role in plant growth, development, and resistance. However, too-high or too-low temperatures or soil drought can limit the growth of , representing a key issue for research. Here, we identified the gene family in the genome and examined its transcriptional responses to cold, drought, and heat stresses. A total of five genes, distributed on four chromosomes and divided into three phylogenetic groups, were identified across the whole genome. Further analysis showed that multiple hormone- and stress-responsive cis-acting elements are located in the promoter regions of s, indicating a potential role of these s in plant growth, development, and response to environmental stresses. Based on existing transcriptome data, s, especially , were found to transcriptionally respond to cold, heat, and drought stresses. Furthermore, quantitative reverse-transcription PCR (qRT-PCR) showed that responds to drought stress in an ABA-dependent manner in stems and leaves and in an ABA-independent manner in roots. These results lay a foundation for functional research on genes in the resistance breeding of the rare and endangered tree species of .