Biology subjects

Delaux, P.-M.

Publications and source records attributed to Delaux, P.-M..

At least 19 recordsLinked to original sources

bioRxiv2026

A single genetic innovation at the origin of plant terrestrialization

How the functional innovations that enabled plants to first colonize land 450 million years ago evolved remains puzzling. Here, we show that the gain of a single family of enzymes was pivotal in the evolution of two of these innovations, the cuticle that protect plants from dehydration and UV light, and the Arbuscular Mycorrhizal symbiosis promoting water and nutrient uptake. We show that functional phosphatase domain Glycerol-3-Phosphate Acyl Transferase (p-GPATs) evolved in the first land plants, concomitantly with the cuticle and symbiosis. Mutation of two p-GPATs from the liverwort Marchantia paleacea is sufficient to abolish both cuticle formation and AM symbiosis, leading to major developmental defects. We propose that the evolution of p-GPATs in land plants acted as a two birds-one stone innovation, diverting intracellular lipids to the extracellular space and providing a simple path to the evolution of two traits essential for the colonization of land.

plant biology↗

bioRxiv2026

Prime-Editing in Marchantia paleacea: Expanding the Genome-Editing Toolbox in Bryophytes

Since the development of CRISPR-based genome editing tools, a number of novel technologies have emerged. This includes Prime-Editing that acts as a search and replace genome editing tool. Prime-Editing has been deployed across multiple clades, including in a few flowering plants. Here, we report on the development of an efficient Prime Editor (PE) for the model bryophyte Marchantia. Initial tests were conducted on Acetolactate Synthase as a target and revealed an average efficiency above 40%. The system has been developed in the GoldenGate cloning system, facilitating construct design. The development of PE in Marchantia expands the Genome-Editing tools available for this emerging model in plant biology.

plant biology↗

bioRxiv2026

The demonstration of a single origin for nodule evolution, with nodule engineering in a non-nodulating species

The nitrogen-fixing root-nodule symbiosis provides a sustainable source of nitrogen for plants within the Nitrogen (N)-fixing clade (NFC). A debate has raged over whether nodulation evolved once, with many losses or multiple times following a predisposition event. Here we demonstrate that nodule-organogenesis is fully conserved between an actinorhizal nodulator Datisca glomerata and the legume Medicago truncatula, showing entirely conserved programmes for Nodule INception (NIN)-controlled development leading to nodule emergence. Convergent losses of N-fixation within the NFC is associated with loss of NIN and we show the engineering of nodule-like development into strawberry, a non-nodulating member of the NFC, through the repair of NIN-functionality. Similar NIN-engineering resulted in altered-root developmental responses in barley. Our work is consistent with the single-gain hypothesis, where repair of NIN can recapitulate nodules in species within the NFC, demonstrating that understanding the ancestral state of nodulation facilitates its engineering.

plant biology↗

bioRxiv2026

Specialised root hair cells facilitate rhizobial infection

Legumes establish symbiotic partnerships with soil bacteria that convert atmospheric nitrogen into plant-available forms. Symbiotic bacteria enter through root hairs following recognition by cell surface receptors that help identify compatible symbionts. However, many root hairs express these receptors, and it has long remained unclear why only a small fraction become infected. Here, we use single-cell transcriptomics to show that legumes pre-specify a rare root hair population for infection before bacterial contact. These susceptible root hairs represent less than one percent of the total, express infection-associated genes prior to encountering symbionts and are conserved in distantly related legumes. Their abundance is regulated by the hormone ethylene and correlates with infection capacity. Our findings reveal that root hair cells do not respond uniformly to symbionts but are instead transcriptionally specialised in advance to control infection entry points. This pre-specification provides a mechanism to balance symbiotic benefits against pathogen infection risks and may exemplify a more general strategy used by multicellular hosts to spatially restrict microbial access.

plant biology↗

bioRxiv2026

The compartmentalized activity of a legume subtilase SBT12a allows symbiosome stabilization

The stabilization of rhizobia in specialized organelles, called symbiosomes, is an evolutionary hallmark for maintaining high rates of nitrogen fixation in legumes. This is achieved by releasing thousands of bacteria from nodular infection threads within in a single plant cell, which poses a great challenge for the host to keep control over these differentiated bacteria. Considering the importance of proteolytic degradation of antimicrobial proteins or generation of symbiosis-promoting peptides, proteolytic activity may represent a key regulatory system. Indeed, we identified the Medicago truncatula subtilisin-like protease (subtilase, SBT) 12a acting as a novel regulator of symbiosome functionality and maintenance. Loss-of-function mutations in SBT12a led to severe symbiotic defects with nodules of sbt12a being characterized by high level induction of defense/senescence-related genes. Using untargeted proteomic High-efficiency Undecanal-based N-Termini EnRichment (HUNTER) we identified and individually confirmed specific SBT12a target proteins that are involved in plant defense responses and symbiosome maintenance. This positions SBT12a as a central host factor controlling symbiosome performance.

plant biology↗

bioRxiv2026

Stepwise evolution of the developmental and symbiotic functions of DELLA in land plants

DELLA proteins play diverse roles in development, plant-microbe interactions and stress responses, and are regulated by the hormone gibberellic acid (GA) in flowering plants. Here, we investigated the evolutionary conservation of functions of the single DELLA ortholog in the non-vascular model liverwort Marchantia paleacea, which lacks genes for perception and biosynthesis of bioactive GA. We found that GA-independent developmental phenotypes are conserved in M. paleacea, while neither DELLA, nor its close paralog GRAS13 are involved in establishment of arbuscular mycorrhizal symbiosis. We propose that symbiosis-related functions of DELLA evolved and have been maintained in vascular plants because GA-dependent regulation offered an additional, systemic, control layer on symbiosis.

plant biology↗

bioRxiv2025

EPP1 is an ancestral component of the plant Common SymbiosisPathway

The success of plants on land has been enabled by mutualistic intracellular associations with microbes for 450 million years (Delaux and Schornack 2021). Because of their intracellular nature, the establishment of these interactions requires tight regulation by the host plants. In particular, three genes - SYMRK, CCaMK and CYCLOPS - form the core of an ancestral common symbiosis pathway (CSP) for intracellular symbioses, and are conserved since the most recent common ancestor of land plants (Radhakrishnan et al. 2020; Delaux et al. 2015; Wang et al. 2010; Parniske 2008). Here, we describe EPP1 as a fourth gene committed to the CSP. Among land plants, EPP1 is conserved only in species able to associate with at least one type of intracellular symbiont. We found that loss-of-function epp1 mutants or EPP1 knock-down lines in four clades of land plants - legumes, Solanaceae, monocots and bryophytes - are all impaired in their ability to associate with arbuscular mycorrhizal fungi. We discovered that the plasma membrane-localized receptor-like SYMRK phosphorylates EPP1 on a conserved serine residue and that this phosphorylation is essential for symbiosis. Using a gain-of-function approach, we demonstrate that EPP1 is upstream of the nuclear kinase CCaMK. We propose that EPP1 is an ancestral component of the essential pathway that has regulated plant symbiosis for half a billion years.

plant biology↗

bioRxiv2025

Nissolia brasiliensis as a non-nodulating model legume

The nitrogen-fixing root nodule symbiosis (RNS) is specifically formed by four orders of angiosperms. The largest of these four orders include the legume family, the Fabaceae. Among legumes, historical model species have emerged, such as the RNS-forming Medicago truncatula and Lotus japonicus, or, more recently, Aeschynomene aevenia. By contrast, legume species that have lost RNS have been largely ignored. Here, we describe the first chromosome-level assembly for a non-RNS-forming legume, the tropical papilionoid Nissolia brasiliensis. We compared its genome to closely related legumes and identified genes associated with RNS. Finally, we developed a stable transformation protocol that can be deployed in the future to re-evolve RNS in legumes, a first step toward the goal of engineering RNS in non-legume crops.

plant biology↗

bioRxiv2025

Leafy liverwort genomes shed light on the evolution of ericoid symbiosis

Symbioses have been fundamental to colonization of terrestrial ecosystems by plants and their evolution. Emergence of the ancient arbuscular mycorrhizal symbiosis was followed by the diversification of alternative intracellular symbioses, such as the ericoid mycorrhizae (ErM). We aimed at understanding how these diversifications occurred. We sequenced the genomes of ErM-forming liverworts, and reconstituted symbiosis under laboratory conditions. We demonstrated the existence of a nutrient-regulated symbiotic state that enables ErM and underlies intracellular colonization of plant tissues. Comparative transcriptomic analyses identified an ancestral gene module associated with intracellular symbiosis beyond ErM. Genetic manipulations in the liverwort Marchantia paleacea, phylogenetics and transactivation assays demonstrated its essential function for intracellular symbiosis. We conclude that plant have maintained, and convergently recruited, an ancestral gene module for intracellular symbioses.

plant biology↗

bioRxiv2025

Exploring fern pathosystems and immune receptors to bridge gaps in plant immunity

Land plants include angiosperms, bryophytes, lycophytes and ferns, each of which may deploy distinct strategies to resist pathogens. Here, we investigate fern-pathogen interactions by characterizing novel pathosystems and analysing the diversity of fern immune receptors. A collection of fern species was inoculated with a diverse set of microbes, and disease symptoms were assessed. We further leveraged published genome mining tools to analyse the diversity of RECEPTOR-LIKE KINASES, RECEPTOR-LIKE PROTEINS (RLKs/RLPs) and NUCLEOTIDE-BINDING AND LEUCINE-RICH REPEATS (NLRs), along with key immune signalling components, in ferns. Our results reveal that ferns exhibit a range of responses to pathogens, including non-host resistance and specific resistance mechanisms. Among ten ferns tested, Pteris vittata displays the broadest spectrum of pathogen compatibility. Genome mining indicates that ferns encode a diverse repertoire of putative immune receptors, antimicrobial peptides and mediators of systemic acquired resistance. Ferns possess numerous RLKs/RLPs, resembling those required for cell-surface immunity in angiosperms. They also encode diverse NLRs, including a previously undescribed class with a disordered N-terminal domain, termed disN-NLR. These findings provide insights into disease resistance evolution and open promising perspectives for crop protection strategies.

plant biology↗

bioRxiv2024

Horizontal gene transfers and terpene metabolism drive plant-fungal interaction in Marchantia polymorpha

The liverwort Marchantia polymorpha has emerged as a model for studying plant immunity in bryophytes, providing unique insights into conserved defense mechanisms across land plants. By contrast, Marchantia-specific immune mechanisms have not been explored. In this study, we investigated the genetic basis of quantitative resistance in M. polymorpha against the fungal pathogen Colletotrichum nymphaeae, a naturally occurring compatible parasite. Through a combination of phenotypic, cytological and transcriptomic approaches, combined with genome-wide association studies (GWAS), we identified key defense-related genes and pathways. Transcriptomic analyses performed on two lines with contrasting suceptibilities to the pathogen revealed a strong overlap in immune responses between M. polymorpha and angiosperms, including the upregulation of PR proteins, transcription factors typically associated with biotic stresses, and enzymes involved in specialized metabolism. Leveraging the biological and genetic variability present in a collection of natural M. polymorpha accessions, highlight the role of horizontally transferred microbial-like terpene synthase (MTPSL) genes, which may contribute to the exceptional terpene diversity in liverworts and play a role in pathogen resistance. GWAS uncovered candidate loci associated with resistance traits, implicating both core immune components and specialized metabolic pathways. These results provide new insights into the specific molecular underpinnings of bryophyte immunity and underscore the evolutionary significance of horizontal gene transfer and specialized metabolites in shaping plant-pathogen interactions.

plant biology↗

bioRxiv2024

Ectomycorrhizal symbiosis evolved independently and by convergent gene duplication in rosid lineages

Many land plants rely on mutualistic symbiotic associations to thrive, starting with their common ancestor associating with arbuscular mycorrhizal (AM) fungi. Similar to AM symbiosis, multiple other intracellular symbiotic interactions have evolved in a variety of land plants. Ectomycorrhizal (ECM) symbiosis contrasts with these relationships as there is no intracellular accommodation of the symbiont inside the plant cell, but only intercellular colonization. This symbiotic relationship is common in a variety of seed plants, mostly trees and shrubs such as pines, willows and oaks. Although it is known which plant lineages are involved in ECM symbiosis, there has been little investigation into the evolutionary origin of ECM symbiosis in these lineages. Furthermore, the genetic innovations and transcriptomic response related to this symbiosis have been studied largely in a genus or species-specific context, which hinders the study of their evolutionary origins. In this study, we reconstruct the origin of ECM in the rosid clade, showing at least 16 independent origins, resulting in the 17 known extant ECM rosid lineages. Moreover, comparative genomics of these lineages highlight genes involved in cell wall remodeling which underwent duplications in a convergent manner across ectomycorrhizal lineages.

plant biology↗

bioRxiv2024

Conservation of an immune homeostasis module in land plants

Calcium-dependent protein kinases (CDPKs) decode cellular calcium transients and play diverse roles in plant growth and stress responses, including immunity. In Arabidopsis thaliana (At, Arabidopsis thereafter), AtCPK28 contributes to immune homeostasis by phosphorylating subgroup IV plant U-box proteins AtPUB22/24/25/26, which target the key immune receptor-like cytoplasmic kinase (RLCK) AtBIK1 for turnover. While this module is conserved in multiple angiosperms, it is unclear if the role of CPK28 in immune homeostasis is conserved more broadly across land plants. Here, we took an evolutionary comparative approach to understand the role of CPK28. We identified a single CPK28 ortholog in the liverwort Marchantia polymorpha, MpCPK28, which exhibits Ca2+-dependent kinase activity that is inhibited by calmodulin in vitro. We identified the subgroup IV plant U-box protein MpPUB20e as a substrate of MpCPK28. MpPUB20e is able to ubiquitinate MpPBLa, the functional ortholog of AtBIK1. We also provide preliminary evidence that MpPBLa undergoes proteasomal degradation in Marchantia, suggesting that optimization of MpPBLa protein accumulation is conserved across land plants. Interestingly, while loss of CPK28 function in multiple angiosperm species results in enhanced immune signaling, we find that Marchantia Mpcpk28 mutant alleles do not display enhanced immune-triggered production of reactive oxygen species or resistance to two pathogens. However, transgenic expression of MpCPK28 was able to restore function in Arabidopsis cpk28-1 mutants, suggesting latent functional conservation of MpCPK28. Furthermore, while AtCPK28-mediated phosphorylation of Thr95/94 on AtPUB25/26 is known to contribute to their activation, we could not observe a functional role for the equivalent residue Thr122 on MpPUB20e. Taken together, our results suggest that post-translational fine-tuning by CPK28 is likely to have refined the PUB-BIK1 module in the vascular plant lineages.

plant biology↗

bioRxiv2024

Conservation of symbiotic signalling across 450 million years of plant evolution

HighlightO_LIThe common symbiotic pathway is activated during arbuscular mycorrhizal symbiosis in Marchantia paleacea C_LIO_LIThe three core members of the common symbiotic pathway are essential for symbiosis in Marchantia paleacea C_LIO_LIThe molecular function of the CCaMK/CYCLOPS module is conserved across land plants C_LIO_LISymbiotic signalling has been conserved in plants for 450 million years C_LI The colonization of land by plants 450 million years ago revolutionized life on Earth1. The fossil record2 and genetic evidence in extant species3 suggest that this transition was facilitated by interactions with symbiotic arbuscular mycorrhizal (AM) fungi4. This ancestral symbiosis relied on the biosynthesis of chemicals by the host plant, both as signals5 and as nutrients3. In angiosperms, a signalling pathway involving the receptor-like kinase SYMRK/DMI26,7, the Calcium and Calmodulin-dependent protein kinase CCaMK/DMI38 and the transcription factor CYCLOPS/IPD39,10 has been described as the common symbiosis pathway (CSP), essential for the establishment of the AM symbiosis and the root-nodule symbiosis11. Phylogenetic and comparative phylogenomic analyses indicated an ancient origin of the CSP, present in all extant land plants forming intracellular symbioses12-15. Trans-complementation assays of the angiosperm mutants with orthologs from diverse species further indicated the conservation of the molecular function of the CSP across the embryophytes9,12,14-16. However, this correlative evidence did not allow testing the ancestral biological function of the CSP. In this study we demonstrate that SYMRK, CCaMK and CYCLOPS are essential for the colonization by AM fungi in bryophytes, indicating that plants have maintained a dedicated signalling pathway to support symbiotic interactions for 450 million years.

plant biology↗

bioRxiv2024

LysM-RLK plays an ancestral symbiotic function in plants

Arbuscular mycorrhiza (AM) with soilborne Glomeromycota fungi was pivotal in the conquest of land by plants almost half a billion years ago. In flowering plants, it is hypothesised that AM is initiated by the perception of AM-fungi-derived chito- and lipochito-oligosaccharides (COs/LCOs) in the host via Lysin Motif Receptor-Like Kinases (LysM-RLKs). However, it remains uncertain whether plant perception of these molecules is a prerequisite for AM establishment and for its origin. Here, we made use of the reduced LysM-RLK complement present in the liverwort Marchantia paleacea to assess the conservation of the role played by this class of receptors during AM and in COs/LCOs perception. Our reverse genetic approach demonstrates the critical function of a single LysM-RLK, LYKa, in AM formation, thereby supporting an ancestral function for this receptor in symbiosis. Binding studies, cytosolic calcium variation recordings and genome-wide transcriptomics indicate that another LysM-RLK of M. paleacea, LYR, is also required for triggering a response to COs/LCOs, despite being dispensable for AM formation. Collectively, our results demonstrate that the perception of symbionts by LysM-RLK is an ancestral feature in land plants, and suggest the existence of yet-uncharacterised AM-fungi signals.

plant biology↗

bioRxiv2024

Annexin and calcium-regulated priming of legume root cells for endosymbiotic infection

Legumes establish endosymbioses with arbuscular mycorrhizal (AM) fungi or rhizobia bacteria to improve mineral nutrition. Symbionts are hosted in privileged habitats, root cortex (for AM fungi) or nodules (for rhizobia) for efficient nutrient exchange. To reach these habitats, plants form cytoplasmic bridges, which are key to predicting and guiding the cellular route of entry of fungal hyphae or rhizobia-filled infection threads (ITs). However, the underlying mechanisms are poorly studied. Here we show that unique ultrastructural changes and Ca2+ spiking signatures, closely linked to MtAnn1 annexin accumulation, accompany rhizobia-associated bridge formation. Loss of MtAnn1 function in M. truncatula affects Ca2+ spike amplitude, cytoplasmic configuration and rhizobia infection efficiency, consistent with a role of MtAnn1 in regulating infection priming. MtAnn1, which evolved in species establishing intracellular symbioses, is also AM-symbiosis-induced and required for proper arbuscule formation. Together, we propose that MtAnn1 is part of an ancient Ca2+-regulatory module for transcellular endosymbiotic infection.

plant biology↗

bioRxiv2023

The Marchantia pangenome reveals ancient mechanisms of plant adaptation to the environment

Plant adaptation to a terrestrial life 450 million years ago played a major role in the evolution of life on Earth. This shift from an aquatic environment has been mostly studied by focusing on flowering plants. Here, we gathered a collection of 133 accessions of the non-vascular plants Marchantia polymorpha and studied its intraspecific diversity using selection signature analyses, genome-environment association study and a gene-centered pangenome. We identified adaptive features shared with flowering plants, such as peroxidases or nucleotide-binding and leucine-rich repeat (NLR), which likely played a role in the adaptation of the first land plants to the terrestrial habitat. The M. polymorpha pangenome also harbored lineage-specific accessory genes absent from seed plants. We conclude that different land plants lineages still share many elements from the genetic toolkit evolved by their most recent common ancestor to adapt to the terrestrial habitat, refined by lineage specific polymorphisms and gene family evolutions.

plant biology↗

bioRxiv2023

Comparative Phylogenomics and Phylotranscriptomics Provide Insights into the Genetic Complexity of Nitrogen Fixing Root Nodule Symbiosis

Plant root nodule symbiosis (RNS) with mutualistic nitrogen-fixing bacteria is restricted to a single clade of angiosperms, the Nitrogen-Fixing Nodulation Clade (NFNC), and is best understood in the legume family. It is widely accepted that nodulation originated through the assembly of modules recruited from existing functions, such as mycorrhizal symbiosis, polar growth, and lateral root development. Because nodulating species are scattered within the NFNC, the number of times nodulation has evolved or has been lost has been a matter of considerable speculation. This interesting evolutionary question has practical implications concerning the ease with which nodulation might be engineered in non-nodulating crop plants. Nodulating species share many commonalities, due either to divergence from a common ancestor over 100 million years ago or to convergence or deep homology following independent origins over that same time period. In either case, comparative analyses of diverse nodulation syndromes can provide insights into constraints on nodulation--what must be acquired or cannot be lost for a functional symbiosis--and what the latitude is for variation in the symbiosis. However, much remains to be learned about nodulation, especially outside of legumes. Here we present new information across the spectrum of nodulating groups. We find no evidence for convergence at the level of amino acid residues or gene family expansion across the NFNC. Our phylogenomic analyses further emphasize the uniqueness of the transcription factor, NIN, as a master regulator of nodulation, and identify key mutations affecting its function across the NFNC. We find that nodulation genes are over-represented among orthologous gene groups (OGs) present in the NFNC common ancestor, but that lineage-specific OGs play major roles in nodulation. We identified over 900,000 conserved noncoding elements (CNEs), of which over 300,000 were unique to NFNC species. A significant proportion of these are associated with nodulation-related genes and thus are candidates for transcriptional regulators.

evolutionary biology↗