Terpenoids form one of the largest classes of plant specialized metabolites, contributing to defense against herbivores and pathogens while also supplying compounds used in pharmaceuticals, fragrances, industrial materials and potential biofuels. Their structural diversity is largely initiated by terpene synthase (TPS) enzymes, but gymnosperms differ from flowering plants in carrying the distinctive TPS-d subfamily, which produces mono-, sesqui- and diterpenoids, including defensive resin compounds. Earlier work was constrained by the enormous and complex genomes of gymnosperms and by functional studies concentrated mainly on a few conifers. Because the origin, expansion and specialization of TPS-d genes across major gymnosperm lineages remain unresolved, in-depth investigation of their evolutionary mechanisms is needed.
Researchers from Zhejiang A&F University, Zhejiang University, Yunnan Academy of Agricultural Sciences, Zhejiang Sci-Tech University and South China Agricultural University conducted the study, published (DOI: 10.1093/hr/uhag195) online on May 20, 2026, in Horticulture Research. Using chromosome-level genomes from ten gymnosperms and six other representative land plants, the team reconstructed the evolution of TPS genes and examined how duplication, protein-sequence divergence and tissue-specific expression shaped the gymnosperm-specific TPS-d lineage. The work further connected these evolutionary patterns with terpenoid accumulation in Torreya grandis, an economically important species in the Taxaceae family.
Across the 16 genomes, the researchers identified 903 putative TPS genes and resolved the gymnosperm-specific TPS-d lineage into three major subclades, with gymnosperms carrying an average of about 65 TPS-d genes per species. A striking 68% of TPS-d genes occurred in tandemly duplicated arrays, whereas phylogenetic patterns provided little support for whole-genome duplication (WGD) as the main driver of expansion. Most inferred tandem duplication (TD) events were concentrated within roughly the past 23 million years, suggesting repeated lineage-specific expansion after major gymnosperm groups had diverged. The team then measured amino acid polymorphism (AAP) and found greater sequence variability in specialized-metabolism TPS lineages than in conserved TPS-c and TPS-e/f groups. Structural modeling and molecular docking of five related enzymes further suggested that duplicated proteins can retain a similar overall fold while developing subtle differences in substrate-binding pockets. Expression analysis using ribonucleic acid sequencing (RNA-seq) datasets showed a parallel regulatory split: tandem-derived TPS-d genes were strongly tissue specialized, with high tissue-specificity index (τ) values. In T. grandis, integrated transcriptomic and metabolomic analyses across six tissues linked distinct TPS expression patterns with distinct terpenoid profiles. Within a tandem cluster associated with diterpene resin acid (DRA) biosynthesis, one candidate gene showed strong aril expression and chloroplast localization, connecting gene-family evolution with tissue-specific chemistry.
The authors said the study presents gene duplication not simply as a way to increase copy number, but as the starting point for evolutionary experimentation. After tandem duplication creates additional TPS-d copies, sequence changes can subtly alter catalytic properties while shifts in gene regulation can redirect activity toward particular tissues. They said this combination helps explain how closely related gymnosperm lineages can build different chemical profiles from a shared ancestral toolkit. The framework also highlights why studying duplicated genes at genomic, structural and expression levels together can reveal functional diversification that would be missed by gene counts alone.
These findings provide a roadmap for identifying terpene-biosynthetic genes in gymnosperms and for prioritizing candidates for biochemical validation. Because terpenoids support plant defense and include commercially valuable natural products, understanding how duplicated TPS genes acquire new functions could eventually inform tree breeding, metabolic engineering and enzyme discovery. The T. grandis case study also shows how comparative genomics can be paired with transcriptomics and metabolomics to connect evolutionary history to tissue-level chemistry. However, the work primarily establishes evolutionary associations and candidate functions; direct enzymatic characterization will still be needed to confirm the products and activities of many duplicated TPS genes. Such validation could turn the evolutionary framework into a practical guide for exploring gymnosperm chemical diversity.
###
References
DOI
10.1093/hr/uhag195
Original Source URL
https://doi.org/10.1093/hr/uhag195
Funding information
2026–2028 Youth Talent Support Program of the Zhejiang Association for Science and Technology (ZAST), Zhejiang A&F University’s Scientific Research Development Fund, National Natural Science Foundation of China (32370661), Major Projects of Zhejiang Province and National Key R&D Program of China.
About Horticulture Research
Horticulture Research is an open access journal of Nanjing Agricultural University and ranked number one in the Horticulture category of the Journal Citation Reports ™ from Clarivate, 2023. The journal is committed to publishing original research articles, reviews, perspectives, comments, correspondence articles and letters to the editor related to all major horticultural plants and disciplines, including biotechnology, breeding, cellular and molecular biology, evolution, genetics, inter-species interactions, physiology, and the origination and domestication of crops.