Sinojackia Hu represents the first woody genus described by Chinese botanists, with all species classified as endangered ornamental plants endemic to China. Their characteristic spindle-shaped fruits confer high ornamental value to the plants, making them favored in gardens and parks. Nevertheless, the fruits likely pose a germination obstacle, contributing to the endangered status of this lineage. Here we report the chromosome-scale genome of S. xylocarpa, and explore the mechanisms underlying its endangered status, as well as its population dynamics throughout evolution. Population genomic analysis has indicated that S. xylocarpa experienced a bottleneck effect following the recent glacial period, leading to a continuous population reduction. Examination of the pericarp composition across six stages of fruit development revealed a consistent increase in the accumulation of lignin and fiber content, responsible for the sturdiness of mature fruits’ pericarps. At molecular level, enhanced gene expression in the biosynthesis of lignin, cellulose and hemicellulose was detected in pericarps. Therefore, we conclude that the highly lignified and fibrotic pericarps of S. xylocarpa, which inhibit its seed germination, should be its threatening mechanism, thus proposing corresponding strategies for improved conservation and restoration. This study serves as a seminal contribution to conservation biology, offering valuable insights for the study of other endangered ornamental plants.

Blooming time is an important basis for constructing plant landscapes. The short flowering period of Osmanthus fragrans, recognized as one of the ten traditional flowers in China, considerably constrains the further utilization of its resources. To clarify O. fragrans flowering regulation, this study focused on OfCOR27, conducting cloning, expression analysis, and functional verification to explore its effects on O. fragrans flowering time. A COR27 phylogenetic tree was built across six species; OfCOR27 physicochemical properties, conserved structures, and promoter cis-elements were analyzed. OfCOR27 CDS was cloned, fusion vectors were transformed into Nicotiana benthamiana, and organ-specific expression was tested in two O. fragrans cultivars. Overexpression vectors were transformed into Arabidopsis thaliana, with qRT-PCR verifying gene function. Five OfCOR27s were identified, showing evolutionary conservation. OfCOR27, which localizes to the nucleus and is associated with flowering regulation, shows higher expression in ‘Sijigui’ than in ‘XiaoyeSugui’. Overexpression of OfCOR27 promoted flowering in A. thaliana, whereas the AtCOR27 mutant flowered later. This confirms OfCOR27 is a positive regulator of plant flowering, which may promote flowering by enhancing the expression of flowering-promoting genes and altering hormone levels, providing a theoretical basis and candidate gene for the genetic improvement of flowering traits in woody ornamental plants.