Biology subjects

Edelbacher, N.

Publications and source records attributed to Edelbacher, N..

6 recordsLinked to original sources

bioRxiv2026

PHOTOTROPIN-mediated blue light signaling orients the asymmetry of Marchantia polymorpha spores

Multicellular organisms produced by sexual reproduction develop from single cells and the asymmetry of these cells can define the orientation of the earliest developmental axes. The haploid multicellular stage of the plant, Marchantia polymorpha, develops from a single cell - the spore - that divides asymmetrically, producing an apical germ cell that generates the plant body and a smaller basal cell that differentiates as an anchoring germ rhizoid cell. We show that the orientation of this asymmetric cell division is controlled by an external, environmental cue - blue light - that is perceived by the photoreceptor PHOTOTROPIN and signals in an NCH1-dependent manner. This defines core elements of the mechanism by which a directional environmental signal orients cell division, which in turn orients the first axis of symmetry.

plant biology↗

bioRxiv2025

Antagonism between blue and red light-signalling controls thallus flatness in Marchantia polymorpha

The growth orientation of the Marchantia polymorpha thallus - a system of dorsiventralized, indeterminate axes - is modulated by light. We show that red and blue light act antagonistically to control thallus growth tropisms, with red light signalling promoting epinasty and blue light signalling promoting hyponasty. We found that loss-of-function mutations in the blue light receptor MpPHOT led to epinasty, while loss-of-function mutations in the red light receptor MpPHY resulted in hyponasty. We hypothesize that these antagonistic activities of blue and red light signalling are balanced in white light, resulting in the development of flat thalli. Using time-resolved transcriptomics, we identified genes that were rapidly induced upon light exposure. Among these genes were all six members of the M. polymorpha BBX gene family. Mutants harbouring loss-of-function mutations in two of the six MpBBX transcription factors developed defective thallus tropisms. Mpbbx1 loss-of-function mutants formed hyponastic thalli, while Mpbbx5 loss-of-function mutants developed epinastic thalli. Double mutants Mpbbx1 Mpbbx5 grew flat, supporting the hypothesis that they function antagonistically. Together, these data indicate that phototropin-mediated blue light and phytochrome-mediated red light signalling antagonistically modulate thallus tropism, and that BBX transcription factors also act antagonistically to regulate thallus flatness.

plant biology↗

bioRxiv2025

De novo meristem development in Marchantia requires light and an apical auxin minimum

Meristems are generative centres with stem cells from which the bodies of land plants develop. Marchantia polymorpha spores are single cell structures formed at meiosis. On germination, spores divide asymmetrically to form a basal cell that terminally differentiates and an apical germ cell that divides into an early cell mass on which a flat prothallus develops. A single stem cell niche (meristem) forms de novo at the margin of the prothallus to drive development of the thallus plant body. Here we show that the prothallus forms at the apical pole of the early cell mass and represses the formation of other prothalli. LOW AUXIN RESPONSIVE (MpLAXR) marks this apical pole indicating that an auxin minimum is located at the site of organogenesis. Light is required for the formation of the apical auxin minimum and for the development of the prothallus from the early cell mass. Disrupting the apical auxin minimum by exogenous auxin treatment suppresses the transitions to the prothallus and formation of the meristem from the early cell mass. A similar molecular program operates during plant regeneration from a single differentiated thallus cell, which regains stemness (pluripotency) upon surgical isolation from surrounding tissues; the isolated cell divides forming an early cell mass that develops a local auxin minimum where a flat prothallus with a single meristem forms. We conclude that a light-dependent, apical auxin minimum is required for the formation of the prothallus and the de novo development of the first meristem in Marchantia polymorpha. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=199 SRC="FIGDIR/small/665278v2_ufig1.gif" ALT="Figure 1"> View larger version (51K): org.highwire.dtl.DTLVardef@c3c93org.highwire.dtl.DTLVardef@15d061borg.highwire.dtl.DTLVardef@3beacdorg.highwire.dtl.DTLVardef@1b45fd4_HPS_FORMAT_FIGEXP M_FIG C_FIG

developmental biology↗

bioRxiv2025

The cytochrome P450 enzyme MpCYP78E1 inhibits meristem initiation and activity in Marchantia polymorpha

Plant shoot branches are formed by the initiation and activation of generative centres known as meristems. In dichotomously branching plants, such as many bryophytes and lycophytes, new meristems are formed when a pre-existing meristem splits into two daughter meristems. These meristems may be active and produce shoot branches or may be inactive. Here, we show that in conditions where meristem inactivation occurs, such as simulated shade, the position of the inactive meristem alternated between either side of the plant body in the liverwort Marchantia polymorpha. Using this predictable pattern, we generated transcriptomes of active and inactive meristems and identified the cytochrome P450 monooxygenase, MpCYP78E1, as a novel regulator of meristem activity. MpCYP78E1 reporter expression was higher in active meristems than inactive meristems. More meristems were active in loss of function mutants than wild type, and fewer meristems were active in gain of function mutants, indicating that MpCYP78E1 inhibits meristem activity. Furthermore, unlike wild type, Mpcyp78e1 loss of function mutants produced supernumerary meristem from the centre of the mature plant body. We conclude that MpCYP78E1 inhibits both meristem initiation and activity to modulate shoot branching architecture.

plant biology↗

bioRxiv2025

High-Throughput Glycan Array Screening Reveals Rhamnogalacturonan-I as a Ligand for Arabidopsis Leucine-Rich Repeat Receptor Kinases

The plant cell wall not only serves as a physical barrier against pathogens but, when damaged, also functions as a source of cell wall-derived molecules that play crucial roles in plant immunity as damage-associated molecular patterns (DAMPs). While oligogalacturonides from homogalacturonan are well-studied DAMPs, the immune-signaling potential of other cell wall components remains largely unexplored. Conventional genetic and biochemical approaches aimed at identifying ligand-receptor pairs in plant immunity have been limited by the vast diversity of potential ligand molecules and functional redundancy of putative receptors. Here, we developed a high-throughput screening pipeline that simultaneously examines multiple interactions between plant cell wall-derived glycans and >350 extracellular domains (ECDs) of receptor kinases and receptor like proteins in Arabidopsis, resulting in the screening of >40,000 interactions. We discovered a group of leucine-rich repeat receptor kinases named ARMs (AWARENESS of RG-I MAINTENANCES) that interact with rhamnogalacturonan-I (RG-I), a major component of pectin. RG-I treatment induced pattern-triggered immunity responses, with distinct kinetics compared to oligogalacturonide responses. We identified RG-I oligosaccharide structures required for interaction with ARM receptors and immune activation, and found that ARM receptors are redundantly involved in plant immunity. Collectively, our approach provides a powerful platform for discovering glycan-receptor pairs in plants, facilitating a more comprehensive understanding of cell wall surveillance mechanisms in plant immunity.

plant biology↗

bioRxiv2024

The three-dimensional anatomy and dorsoventral asymmetry of the mature Marchantia polymorpha meristem develops from a symmetrical gemma meristem

Meristems are three-dimensional generative structures that maintain a population of stem cells whilst producing new organs and tissues. Meristems develop in all land plants, however we know relatively little about the spatial and temporal regulation of meristem structure in lineages such as the bryophytes. Here we describe the three-dimensional anatomy of the meristem during the development of the liverwort, Marchantia polymorpha. Using optical reconstructions of the frontal, sagittal and transverse planes through the mature meristem, we show that the apical stem cell is sub-apical, ventral, and located in the outer cell layer. The anatomy of the mature meristem is therefore asymmetrical in the dorsoventral axis, which is reflected by the domain specific protein localisation of Marchantia Class III and Class IV Homeodomain-Leucine-Zippers (MpC3HDZ and MpC4HDZ) and promoter activity of MpYUCCA2. The dorsoventral asymmetry that defines the mature meristem is absent in the juvenile meristems of the asexual propagules known as gemmae. We discovered that anatomical dorsoventral asymmetry of the meristem forms after two days of gemmaling growth and is accompanied by expression of the dorsal identity reporter, MpC3HDZ. We conclude that the gemma meristem is in a state of arrested development and undergoes anatomical rearrangement to develop the three-dimensional meristem structure of the mature plant.

plant biology↗