Su, J.-C. | bioRxiv Science

bioRxiv2024

A Sap Peptide Conserved across Flowering Plants Positively Regulates Lignin Biosynthesis, Biomass and Immunity

Signaling peptides act as hormones to deliver short- or long-distance intercellular signals to govern complex developmental processes. Identifying endogenous signaling peptides is challenging due to their low abundance and the unknown cleavage sites required for release from precursor proteins, not to mention the investigation of their evolutionary roles across species. Consequently, very few peptides were evolutionarily characterized in vivo, especially long-distance signaling peptides. Here we present current largest peptidomic datasets from six species (maize, camphor tree, tomato, rose gum, soybean and poplar), totaling 12,242 peptides, selected from all representative evolutionary clades of angiosperms, including monocots, magnoliids, rosid eudicots, and asterid eudicots. A sap peptide was found to be identical across all six species and named as ASAP (angiosperm sap peptide), emerging as the most conserved peptide family discovered thus far. ASAP rapidly induces a series of protein phosphorylation involved in a signaling cascade previously reported to regulate lignin biosynthesis, plant growth and plant immunity. Functional assays on ASAP activity demonstrated its capability on the induction of monolignol biosynthesis and lignin deposition. High-throughput phenomic analyses showed that ASAP significantly increased plant above- and below-ground biomass. In addition, ASAP treatment enhanced plant immunity and reduced the number of galls and egg masses against nematode invasion. This study provides insights into the conservation and functional significance of plant long-distance mobile signaling peptides, offering potential applications in crop improvement and disease management strategies.

plant biology↗

bioRxiv2021

Single-cell transcriptomics unveils xylem cell development and evolution

As the most abundant tissue on Earth1, 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 cells2. 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 plants2. 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, here we 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 trichocarpa and Eucalyptus grandis share nearly identical fusiform lineages. The tracheids in the basal eudicot Trochodendron aralioides, an evolutionarily reversed character3, 4, exhibit strong transcriptomic similarity to vessel elements but not libriform fibers, suggesting that water transportation, instead of mechanical support, is the major feature. We also found that the more basal angiosperm Liriodendron chinense has 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 history5.

plant biology↗