This work shows that the conserved CLAVATA3 peptide (CLV3p)-receptor stem cell signaling pathway represses vascular transcriptional programs in the shoot apical meristem, thereby preventing ectopic vascular differentiation in the stem center, and quantitatively regulates peripheral VB number.
Abstract
Terrestrial plant biomass relies on the formation of vascular bundles (VBs) comprising xylem, cambial, and phloem cells that drive secondary growth and wood formation. How VB formation and organization is coordinated with stem growth remains unclear. Here, we show that the conserved CLAVATA3 peptide (CLV3p)-receptor stem cell signaling pathway represses vascular transcriptional programs in the shoot apical meristem (SAM), thereby preventing ectopic vascular differentiation in the stem center, and quantitatively regulates peripheral VB number. Mutational analysis of conserved CLV3p residues partially uncouples its roles in vascular differentiation from stem cell maintenance. However, overexpression and mutational analysis with key phloem regulators reveals that CLV3p controls vascular and stem cell programs via a DOF (DNA-BINDING WITH ONE FINGER) and SMXL (SUPPRESSOR OF MAX2 1-LIKE) transcriptional module. Our findings identify a novel role for CLV3p signaling in shoot vascular development and establish a regulatory framework integrating stem cell signaling with vascular patterning.
A positive feedback loop between CLV3 and WUS that is mediated by multiple hormone interactions, which is critical for plants to adapt to harsh environments is revealed.
Mengchu Xu, Haijun Wu, Chengwu Liu et al.· Molecular Plant· 0 citations
Auxin Response Factors (ARFs) are of vital importance in plant growth and vascular development. Class A ARFs are the core auxin-driven drivers of embryogenesis, vascular pattern development, (pro)cambial stem cell initiation and xylem cell fate specification, while class B ARFs may attenuate or fine-tune auxin-mediated development. The potential roles of class C ARFs in vascular development and xylogenesis, however, remain largely unexplored. In this study, we identified Eucalyptus grandis ARF10 (EgrARF10) as a potential regulator of secondary cell wall (SCW) development. We show that EgrARF10 is nucleus-localised and strongly associated with SCW biosynthetic genes and transcription factors across co-expression and multi-omic networks. Mining of published spatial and single cell transcriptomic data revealed preferential expression of EgrARF10 in vessel and fusiform organizer cells of secondary xylem tissue, while EgrARF10 orthologs in other species exhibit diverse cell type-specific expression ranging from root cap vascular and metaxylem to cork cambium. Heterologous overexpression of EgrARF10 in hybrid poplar did not alter overall growth or morphology but resulted in a significant reduction in stem lignification, accompanied by relative increases in D-glucose, D-xylose and D-mannose, indicating altered SCW composition. While the molecular mechanism by which EgrARF10 acts remains unknown, these findings provide the first evidence for the role of a class C ARF in xylem SCW biology.
Ipeleng Makhura, R. Ployet, A. Myburg et al.· Tree Genetics & Genomes· 0 citations
Secondary xylem differentiation determines wood structure and function in perennial plants, yet its regulatory mechanisms remain poorly understood in Hevea brasiliensis. Here, we generated a single-nucleus RNA sequencing (snRNA-seq) atlas from the cambium to mature xylem region in stems, resolving transcriptionally distinct cell populations corresponding to cambium, xylem mother cells, and fibre-vessel cells. Pseudotime analysis reconstructed the developmental trajectories from cambium to late xylem cell states and revealed stage-specific activation of secondary cell wall (SCW) biosynthesis programmes. Gene regulatory network analysis identified HbWRKY12a as a fibre-vessel enriched transcription factor functioning as a key regulator in SCW formation. Molecular assays demonstrated that HbWRKY12a directly binds and activates HbMYB1R1c, which subsequently modulates lignin-associated SCW deposition. Heterologous overexpression of either HbWRKY12a or HbMYB1R1c in Arabidopsis resulted in significant reductions in stem diameter and plant height. Both overexpression lines exhibited markedly decreased SCW thickness in fibre, vessels, and pith cells. These findings reveal a WRKY-MYB cascade that mediates SCW formation in H. brasiliensis, extending the classical NAC-MYB regulatory framework and providing molecular targets for improving xylem properties and stress resilience in tropical perennial crops.
Jinjing Pan, Yanhong Xu, Junchao Zhao et al.· Plant, Cell and Environment· 0 citations
Pollen wall formation requires precise coordination between tapetum differentiation, metabolism, and programmed cell death. In Arabidopsis, the microspore-derived peptide CLE19 restricts tapetal activity to maintain pollen wall homeostasis, yet how CLE19 signaling achieves developmental specificity and robustness remains unclear. Here, we identify the receptor-like kinase BARELY ANY MERISTEM 3 (BAM3) as an additional receptor for CLE19. Genetic, cytological, biochemical, and transcriptomic analyses showed that disruption of BAM3 signaling impairs tapetum differentiation, secretory homeostasis, and pollen exine patterning, resulting in selective transcriptional reprogramming during anther development. Comparative transcriptomic analyses reveal that BAM3 mediates a distinct subset of CLE19-responsive genes, including both AMS-dependent pathways governing tapetal degeneration and exine biosynthesis, and AMS-independent programs associated with flavonoid metabolism and pollen wall development. Biochemical assays, structure-guided mutagenesis, and AlphaFold3 modeling further support CLE19-dependent assembly of BAM3-SERK1/2 receptor complex, revealing a conserved molecular framework for CLE19 perception that is distinct from, yet complementary to, the previously characterized CLE19-PXL1-SERK1/2 receptor module. Together, these findings establish a dual-receptor architecture for CLE19 signaling in which BAM3 mediates a transcriptionally distinct branch of the CLE19 pathway. More broadly, this work demonstrates how combinatorial peptide-receptor usage expands the signaling capacity of a single developmental peptide to coordinate robust male reproductive development.
Wenhui Sun, S. Wang, Mengyu Li et al.· Plant Physiology· 0 citations
It is reported that NtProRP1, an extracellular protein, localizes to the cell wall immediately after fertilization in Nicotiana tabacum, uncovering a new mechanism for NtProRP1 in regulating early embryogenesis and delivering a unique transcriptomic resource that advances understanding of extracellular signaling in plant embryogenesis.
An Luo, Ying Qiao, Siyuan Li et al.· Plant and Cell Physiology· 0 citations
The root meristem is essential for stem cell maintenance and root development in plants. In Arabidopsis, Root meristem Growth Factor (RGF) peptides and their receptors regulate root meristem size through reactive oxygen species (ROS)-dependent signalling. RGF1-mediated ROS redistribution post-translationally stabilises the root meristem master regulator PLETHORA2 (PLT2). Although genomic studies suggest that RGF–receptor modules are evolutionarily conserved across land plants, their functional characterisation has remained largely limited to Arabidopsis. Here, we show that Oryza sativa RGF1-1 (OsRGF1-1) functions as a rice homologue of Arabidopsis RGF1 (AtRGF1). CRISPR/Cas9-generated Osrgf1-1 mutants exhibited shorter seminal roots, reduced root meristem size, and decreased superoxide (O₂•⁻) accumulation. EdU staining further confirmed that cell proliferation activity was reduced in the Osrgf1-1 mutants. The Osrgf1-1 mutants were sensitive to low concentrations of chemically synthesised mature OsRGF1-1 peptide. This low dose of OsRGF1-1 peptide restored seminal root growth and O₂•⁻ accumulation in the Osrgf1-1 mutants but had no detectable effect on the wild type. Functional analyses using Arabidopsis rgfr receptor mutants further demonstrated that OsRGF1-1 is perceived through conserved RGF receptor machinery. Together, our findings provide the first functional evidence that the RGF1–receptor–ROS signalling module is evolutionarily conserved between dicots and monocots in the regulation of root meristem development.
Joon-Keat Lai, Jhen-Ni Jhang, Hong-Chun Yen et al.· bioRxiv· 0 citations