The evolution of xylem reflects a progressive simplification, moving from gymnosperms to angiosperms.
Wood, produced by xylem, provides structural support and long-distance water transport, constituting a major fraction of Earth’s plant biomass. However, tracking how individual xylem cells differentiate has been computationally challenging because developing wood contains many cell types and stages at once. As noted in the editor’s commentary “A needle in the haystack,” the specific signals of transient developmental stages are masked by high-dimensional noise arising from the complex tissue background.
To search for that “needle,” an interdisciplinary team from the Department of Life Science at National Taiwan University (Profs. Te-Lun Mai and Ying-Chung Jimmy Lin) and the Department of Biotechnology and Bioindustry Sciences at National Cheng Kung University (Prof. Ying-Lan Chen), in collaboration with the University of California, Davis, tackled this problem by constructing a high-dimensional multi-omics atlas. The study is published in The Plant Cell.
They integrated single-cell transcriptomics with spatial transcriptomics, proteomics, and metabolomics to profile differentiating xylem in the conifer Cunninghamia lanceolata and to compare these data with those of four flowering species.
By applying cross-species data integration algorithms, the team mapped cell states from diverse species onto a single shared landscape. This analysis revealed a clear pattern: while gymnosperms utilize more complex developmental pathways, angiosperms occupy only simplified subsets of them. Spatial data validated this pattern and supported a “code cleanup” model of evolution. Instead of building new features, the developmental program appears to have been streamlined by deleting parts of the “original code,” a process of reductive evolution.
This challenges the view that evolution mostly adds features; instead, this computational analysis demonstrates that reducing the program to its essentials is also an effective evolutionary strategy in seed plant wood.
In short, these findings support a model of “reductive evolution” in seed plant wood: rather than gaining complexity, angiosperm xylem appears to have emerged by gradually simplifying an ancestrally elaborate axial program.
“These data provide a framework for future studies of xylem biology and plant adaptation,” said Prof. Te-Lun Mai, who directed the bioinformatics and modeling efforts, together with Prof. Ying Chung Jimmy Lin at National Taiwan University. Leveraging this computational framework, the team has also investigated tension wood, a special type of xylem formed under mechanical stress that may be used to fine-tune wood properties and biomass yield in the future.
Prof. Te-Lun Mai's email address: [email protected]
Prof. Ying-Chung Jimmy Lin’s email address: [email protected]
