Single-Cell Transcriptomics Unveils Xylem Cell Development and Evolution

As the most abundant tissue on Earth, xylem is responsible for lateral growth in plants. Typical xylem has a radial system composed of ray parenchyma cells and an axial system of fusiform cells. In most angiosperms, fusiform cells are a combination of vessel elements for water transportation and libriform fibers for mechanical support, while both functions are performed together by tracheids in other vascular plants. However, little is known about the developmental programs and evolutionary relationships of these xylem cell types. Through both single-cell and laser-capture microdissection transcriptomic profiling, the research team led by Ying-Chung Jimmy Lin(林盈仲) from the NTU Institute of Plant Biology, PhD students Chia-Chun Tung (董家均), Shang-Che Kuo (郭尚哲), Jhong-He Yu (余中合), and Assistant Research Fellow Chuan Ku (顧銓) from the Institute of Plant and Microbial Biology, Academia Sinica, demonstrate the developmental lineages of ray and fusiform cells in stem-differentiating xylem across four divergent woody angiosperms. Cross-species analyses of single-cell trajectories reveal highly conserved ray, yet variable fusiform, lineages across angiosperms. Core eudicots Populus trichocarpaandEucalyptus grandisshare nearly identical fusiform lineages. The tracheids in the basal eudicotTrochodendron aralioides, an evolutionarily reversed character, exhibit strong transcriptomic similarity to vessel elements but not libriform fibers, suggesting that water transportation, instead of mechanical support, is the major feature. They also found that the more basal angiospermLiriodendron chinensehas a fusiform lineage distinct from that in core eudicots. This evo-developmental framework provides a comprehensive understanding of the formation of xylem cell lineages across multiple plant species spanning over a hundred million years of evolutionary history.

Click the link to read the article: https://genomebiology.biomedcentral.com/articles/10.1186/s13059-022-02845-1