Chimonanthus praecox, also known as wintersweet, is a traditional ornamental plant in China. It blooms during the cold winter months and emits a long-lasting fragrance. The WUSCHEL-related homeobox (WOX) transcription factor family is a plant-specific family of homeodomain (HD) transcription factors that plays diverse roles in plant development. We identified 13 WOX family genes (CpWOX1–CpWOX12 and CpWUS) and systematically analysed their physicochemical properties, evolutionary relationships, conserved domains, and expression regulation characteristics. The subcellular localization prediction indicates that all CpWOX proteins are localized in the nucleus and contain a conserved homeobox domain, with the WUS clade specifically containing a WUS-box motif. Phylogenetic analysis revealed that these genes are divided into three evolutionary branches: the WUS, ancient, and intermediate clades. Promoter analysis suggests that CpWOX genes may be involved in hormone responses, abiotic stress, developmental regulation, and encodes a nuclear-localised protein with self-activating activity. It is highly expressed in the stamen and root and is induced by low and high temperatures, salt stress, and methyl jasmonate. This study revealed the evolutionary characteristics of the WOX family genes in wintersweet and the function of CpWUS in regulating flowering time and root development, providing a theoretical basis for understanding the developmental regulatory mechanisms in wintersweet.

Chimonanthus praecox, a traditional ornamental plant in China, is admired for its ability to bloom during the cold winter season and is recognized as an outstanding woody cut flower. MADS-box genes encode transcription factors essential for plant growth and development, with key functions in regulating flowering time and the formation of floral organs. In this study, 74 MADS-box genes (CpMADS1–CpMADS74) were identified and mapped across 11 chromosomes, with chromosome 1 harboring the highest number (13 genes) and chromosome 3 the fewest (3 genes). Physicochemical property analysis revealed that all CpMADS proteins are hydrophilic and predominantly nuclear-localized. Phylogenetic analysis classified these genes into Type I and Type II subfamilies, highlighting a clear divergence in domain structure. Eighty simple sequence repeat (SSR) loci were detected, with dinucleotide repeats being the most abundant, and the majority located in Type II MADS genes. From 23 C. praecox samples, 10 polymorphic SSR markers were successfully developed and PCR-validated, enabling a cluster analysis that grouped these cultivars into three distinct clusters. This study offers significant insights into the regulation of flowering, floral organ development, genetic linkage map construction, and the application of marker-assisted selection in C. praecox.