Chromosome-scale genome of Ormosia hosiei provides insights into legume tree genome evolution

BACKGROUND: Ormosia hosiei, commonly known as the "Chinese love bean tree" for its traditional symbolic association with love and longing in Chinese literature, is an economically and ecologically important leguminous tree species endemic to China, prized for its high-density hardwood and its vital ecological functions in subtropical forests. However, the limited availability of genomic resources has hindered in-depth molecular studies, constraining both genetic improvement efforts-such as those targeting wood formation-and conservation strategies. RESULTS: In this study, we present a high-quality genome assembly of O. hosiei with a total size of 2.14 Gb and a scaffold N50 of 255.85 Mb, and annotated 39,309 protein-coding genes. Extensive identification and characterization of Gypsy and Copia LTR retrotransposon subfamilies revealed their major contribution to genome size expansion. Whole-genome duplication (WGD) analysis revealed that O. hosiei has experienced two WGD events: an ancient event shared broadly across leguminous species, and a more recent duplication likely shared within the Genistoid clade, including multiple Ormosia species. Furthermore, we identified 117 NAC and 176 MYB transcription factors in O. hosiei, including VND-like and MYB46-/83-like genes that are central regulators of secondary cell wall biosynthesis. These genes likely contribute to wood formation and the development of straight trunk architecture. CONCLUSIONS: Overall, the O. hosiei reference genome provides a valuable genomic resource for understanding legume evolution and offers essential support for functional genomics studies, molecular breeding, and conservation of this precious timber species endemic to China.