Biology subjects

Coudert, Y.

Publications and source records attributed to Coudert, Y..

5 recordsLinked to original sources

bioRxiv2026

Robust planar morphogenesis in leaf-like organs requires callose-dependent coordination of division and growth

Planar organs, such as leaves, are key developmental innovations underlying the evolutionary success of plants. In vascular plants, building a planar organ requires coordinating cell division and growth both within the organ plane and across multiple, mechanically distinct cell layers. Phyllids, the leaf-like organs of bryophytes, typically consist of a single cell layer and offer a minimal system to decouple in-plane growth coordination from inter-layer mechanics. Here, we investigate how robust planar morphogenesis is achieved in phyllids, using the moss Physcomitrium patens as a bryophyte model. We show that impaired cytokinesis, caused by the loss of a callose synthase gene, disrupts growth gradients, ultimately yielding smaller, non-planar organs of variable shape. Combining quantitative live imaging with computational modeling, we show that the severity of shape defects in mutants depends on the spatial distribution and developmental timing of local growth arrests. These findings reveal how callose-dependent coordination between cell division and in-plane growth prevents mechanical conflicts and maintains planarity in a monolayered plant organ.

plant biology↗

bioRxiv2026

Decarboxylation of indoleacetic acid illuminates its evolution into a plant hormone

The evolution of indoleacetic acid (IAA) into the plant hormone auxin remains unclear. Here, we compared IAA response and metabolism in land plants and their closest living relatives, the streptophyte algae, using chemical treatments, phytohormone profiling, and targeted and untargeted metabolomics. Streptophyte algae showed neither plant-like auxin responses nor canonical IAA metabolism. Here, we demonstrate IAA side-chain decarboxylation as a novel pathway of cellular IAA metabolism, operating in streptophyte algae and land plants alike. Decarboxylation also underpinned IAA's innate photolability and yielded cytotoxic intermediates, which also accumulated endogenously under simulated sunlight. Together, these findings establish IAA decarboxylation as a major, conserved metabolic pathway, and suggest that the metabolic constraints arising from IAA's instability and indirect cytotoxicity contributed to its adoption as a plant hormone.

plant biology↗

bioRxiv2026

Near-equiprobable binary branching decisions underlie filament patterning in the moss Physcomitrium patens

Branching forms are ubiquitous in nature and have evolved repeatedly across scales and species. An important goal of developmental biology remains to identify similarities and differences in the regulatory mechanisms underlying branching. Here, we investigate the branching filaments that form upon spore germination in mosses, using Physcomitrium patens as a model species. To identify the macroscopic rules governing filament patterning, we developed a pipeline to acquire high-resolution 3D images of whole sporelings, reconstruct filament architecture at single-cell resolution, and formalize cell organization using mathematical tree representations. Our quantitative analysis reveals that branch patterning in moss filaments can be captured by a simple probabilistic model in which subapical cells have a near-equal probability of producing - or not producing - a side-branch between successive apical cell divisions. This framework provides a quantitative basis for comparing the developmental rules driving branching morphogenesis within and beyond the plant kingdom.

plant biology↗

bioRxiv2026

Evolution of moss leaf-like organs through variations in deeply conserved developmental principles

Leaves and leaf-like organs with laminar structures and determinate growth arose multiple times independently in land plants. The cellular basis of leaf development is well characterized in flowering plants, and molecular studies have shown that the plant hormone auxin plays a central role in this process, orchestrating cellular growth and differentiation. Auxin is also crucial for the formation of phyllids, the leaf-like organs of bryophytes, yet its precise role in morphogenesis remains unclear. More broadly, whether similar developmental principles are shared across distantly related evolutionary lineages is unknown. Here, we combine live-imaging, genetics, pharmacological treatments, and modeling to investigate the cellular and molecular basis of phyllid development in the model moss Physcomitrium patens. By tracking phyllid morphogenesis from a single initial cell to full maturity, we uncover the cellular growth dynamics underlying organ development. We demonstrate that auxin spatially inhibits cell divisions and promotes cellular elongation and differentiation. However, unlike in vascular plants, moss PIN transporters do not participate in polar auxin transport during phyllid development but mainly reduce intracellular auxin concentration. These findings indicate that while auxins role in organogenesis is conserved, its transport mechanisms have diverged across land plants. Overall, our study reveals shared principles of planar organ morphogenesis, highlighting how the repeated deployment of similar developmental strategies, with lineage-specific variations, drove the convergent evolution of leaves and leaf-like organs. One-Sentence SummaryAuxin modulates a conserved developmental program in moss leaf-like organs by spatiotemporally controlling cell division and growth.

plant biology↗

bioRxiv2022

Apical and basal auxin sources pattern shoot branching in a moss

Shoot branching mechanisms where branches arise in association with leaves - referred to as lateral or axillary branching - evolved by convergence in the sporophyte of vascular plants and the gametophyte of bryophytes, and accompanied independent events of plant architectural diversification1. Previously, we showed that three hormonal cues, including auxin, have been recruited independently to co-ordinate branch patterning in flowering plant leafy shoots and moss gametophores (Coudert, Palubicki et al., 2015)2-4. Moreover, auxin-mediated apical dominance, which relies on local auxin production, has been proposed as a unifying molecular regulatory mechanism of branch development across land plants5. Whilst our previous work in the moss Physcomitrium patens has gathered indirect evidence supporting the notion that auxin synthesized in gametophore apices regulates branch formation at a distance2, direct genetic evidence for a role of auxin biosynthesis in gametophore branching control is still lacking. Here, we show that gametophore apex decapitation promotes branch emergence through massive and rapid transcriptional reprogramming of auxin-responsive genes and altering auxin biosynthesis gene activity. Specifically, we identify a subset of P. patens TRYPTOPHAN AMINO-TRANSFERASE (TAR) and YUCCA FLAVIN MONOOXYGENASE-LIKE (YUC) auxin biosynthesis genes expressed in apical and basal regions of the gametophore, and show that they are essential for branch initiation and outgrowth control. Our results demonstrate that local auxin biosynthesis coordinates branch patterning in moss and thus constitutes a shared and ancient feature of shoot architecture control in land plants.

plant biology↗