Publications by authors named "Katharina Schiessl"

10 Publications

  • Page 1 of 1

Molecular mechanism of cytokinin-activated cell division in .

Science 2021 03 25;371(6536):1350-1355. Epub 2021 Feb 25.

Sainsbury Laboratory, University of Cambridge, Bateman Street, Cambridge CB2 1LR, UK.

Mitogens trigger cell division in animals. In plants, cytokinins, a group of phytohormones derived from adenine, stimulate cell proliferation. Cytokinin signaling is initiated by membrane-associated histidine kinase receptors and transduced through a phosphorelay system. We show that in the shoot apical meristem (SAM), cytokinin regulates cell division by promoting nuclear shuttling of Myb-domain protein 3R4 (MYB3R4), a transcription factor that activates mitotic gene expression. Newly synthesized MYB3R4 protein resides predominantly in the cytoplasm. At the G2-to-M transition, rapid nuclear accumulation of MYB3R4-consistent with an associated transient peak in cytokinin concentration-feeds a positive feedback loop involving importins and initiates a transcriptional cascade that drives mitosis and cytokinesis. An engineered nuclear-restricted MYB3R4 mimics the cytokinin effects of enhanced cell proliferation and meristem growth.
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http://dx.doi.org/10.1126/science.abe2305DOI Listing
March 2021

NODULE INCEPTION Recruits the Lateral Root Developmental Program for Symbiotic Nodule Organogenesis in Medicago truncatula.

Curr Biol 2019 11 19;29(21):3657-3668.e5. Epub 2019 Sep 19.

Sainsbury Laboratory, Cambridge University, Bateman Street, Cambridge CB2 1LR, UK; Department of Cell and Developmental Biology, John Innes Centre, Norwich Research Park, Colney Lane, Norwich NR4 7UH, UK. Electronic address:

To overcome nitrogen deficiencies in the soil, legumes enter symbioses with rhizobial bacteria that convert atmospheric nitrogen into ammonium. Rhizobia are accommodated as endosymbionts within lateral root organs called nodules that initiate from the inner layers of Medicago truncatula roots in response to rhizobial perception. In contrast, lateral roots emerge from predefined founder cells as an adaptive response to environmental stimuli, including water and nutrient availability. CYTOKININ RESPONSE 1 (CRE1)-mediated signaling in the pericycle and in the cortex is necessary and sufficient for nodulation, whereas cytokinin is antagonistic to lateral root development, with cre1 showing increased lateral root emergence and decreased nodulation. To better understand the relatedness between nodule and lateral root development, we undertook a comparative analysis of these two root developmental programs. Here, we demonstrate that despite differential induction, lateral roots and nodules share overlapping developmental programs, with mutants in LOB-DOMAIN PROTEIN 16 (LBD16) showing equivalent defects in nodule and lateral root initiation. The cytokinin-inducible transcription factor NODULE INCEPTION (NIN) allows induction of this program during nodulation through activation of LBD16 that promotes auxin biosynthesis via transcriptional induction of STYLISH (STY) and YUCCAs (YUC). We conclude that cytokinin facilitates local auxin accumulation through NIN promotion of LBD16, which activates a nodule developmental program overlapping with that induced during lateral root initiation.
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http://dx.doi.org/10.1016/j.cub.2019.09.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6839406PMC
November 2019

and Are Essential for Indeterminate Nodule Identity.

Plant Physiol 2018 09 19;178(1):295-316. Epub 2018 Jul 19.

Institute of Plant Sciences Paris-Saclay IPS2, Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique, Université Paris-Sud, Université Evry, Université Paris-Saclay, Bâtiment 630, 91405 Orsay, France

Symbiotic interactions between legume plants and rhizobia result in the formation of nitrogen-fixing nodules, but the molecular actors and the mechanisms allowing for the maintenance of nodule identity are poorly understood. (), (), and () are orthologs of Arabidopsis () and are members of the gene family, which has conserved roles in plant development and is essential for indeterminate and determinate nodule identity in legumes. The loss of function of , , and triggers a partial loss of nodule identity characterized by the development of ectopic roots arising from nodule vascular meristems. Here, we report the identification and characterization of a second gene involved in regulating indeterminate nodule identity in , is the paralog of and belongs to a second legume-specific subclade, the clade. expression was induced during early nodule formation, and it was expressed primarily in the nodule central meristem. mutants did not present any particular symbiotic phenotype; however, the loss of function of both and resulted in the complete loss of nodule identity and was accompanied by drastic changes in the expression of symbiotic, defense, and root apical meristem marker genes. double mutants developed only nonfixing root-like structures that were no longer able to host symbiotic rhizobia. This study provides original insights into the molecular basis underlying nodule identity in legumes forming indeterminate nodules.
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http://dx.doi.org/10.1104/pp.18.00610DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6130032PMC
September 2018

DELLA genes restrict inflorescence meristem function independently of plant height.

Nat Plants 2017 Sep 21;3(9):749-754. Epub 2017 Aug 21.

Cell and Developmental Biology Department, John Innes Centre, Norwich Research Park, Norwich, NR4 7UH, UK.

DELLA proteins associate with transcription factors to control plant growth in response to gibberellin . Semi-dwarf DELLA mutants with improved harvest index and decreased lodging greatly improved global food security during the 'green revolution' in the 1960-1970s . However, DELLA mutants are pleiotropic and the developmental basis for their effects on plant architecture remains poorly understood. Here, we show that DELLA proteins have genetically separable roles in controlling stem growth and the size of the inflorescence meristem, where flowers initiate. Quantitative three-dimensional image analysis, combined with a genome-wide screen for DELLA-bound loci in the inflorescence tip, revealed that DELLAs limit meristem size in Arabidopsis by directly upregulating the cell-cycle inhibitor KRP2 in the underlying rib meristem, without affecting the canonical WUSCHEL-CLAVATA meristem size regulators . Mutation of KRP2 in a DELLA semi-dwarf background restored meristem size, but not stem growth, and accelerated flower production. In barley, secondary mutations in the DELLA gain-of-function mutant Sln1d also uncoupled meristem and inflorescence size from plant height. Our work reveals an unexpected and conserved role for DELLA genes in controlling shoot meristem function and suggests how dissection of pleiotropic DELLA functions could unlock further yield gains in semi-dwarf mutants.
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http://dx.doi.org/10.1038/s41477-017-0003-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5669458PMC
September 2017

Active Control of Cell Size Generates Spatial Detail during Plant Organogenesis.

Curr Biol 2015 Nov 29;25(22):2991-6. Epub 2015 Oct 29.

Cell and Developmental Biology Department, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK. Electronic address:

How cells regulate their dimensions is a long-standing question. In fission and budding yeast, cell-cycle progression depends on cell size, although it is still unclear how size is assessed. In animals, it has been suggested that cell size is modulated primarily by the balance of external signals controlling growth and the cell cycle, although there is evidence of cell-autonomous control in cell cultures. Regardless of whether regulation is external or cell autonomous, the role of cell-size control in the development of multicellular organisms remains unclear. Plants are a convenient system to study this question: the shoot meristem, which continuously provides new cells to form new organs, maintains a population of actively dividing and characteristically small cells for extended periods. Here, we used live imaging and quantitative, 4D image analysis to measure the sources of cell-size variability in the meristem and then used these measurements in computer simulations to show that the uniform cell sizes seen in the meristem likely require coordinated control of cell growth and cell cycle in individual cells. A genetically induced transient increase in cell size was quickly corrected by more frequent cell division, showing that the cell cycle was adjusted to maintain cell-size homeostasis. Genetically altered cell sizes had little effect on tissue growth but perturbed the establishment of organ boundaries and the emergence of organ primordia. We conclude that meristem cells actively control their sizes to achieve the resolution required to pattern small-scale structures.
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http://dx.doi.org/10.1016/j.cub.2015.10.008DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4651904PMC
November 2015

Crystal structure of PhnZ in complex with substrate reveals a di-iron oxygenase mechanism for catabolism of organophosphonates.

Proc Natl Acad Sci U S A 2014 Apr 21;111(14):5171-6. Epub 2014 Mar 21.

Department of Biomedical and Molecular Sciences, Queen's University, Kingston, ON, Canada K7L 3N6.

The enzymes PhnY and PhnZ comprise an oxidative catabolic pathway that enables marine bacteria to use 2-aminoethylphosphonic acid as a source of inorganic phosphate. PhnZ is notable for catalyzing the oxidative cleavage of a carbon-phosphorus bond using Fe(II) and dioxygen, despite belonging to a large family of hydrolytic enzymes, the HD-phosphohydrolase superfamily. We have determined high-resolution structures of PhnZ bound to its substrate, (R)-2-amino-1-hydroxyethylphosphonate (2.1 Å), and a buffer additive, l-tartrate (1.7 Å). The structures reveal PhnZ to have an active site containing two Fe ions coordinated by four histidines and two aspartates that is strikingly similar to the carbon-carbon bond cleaving enzyme, myo-inositol-oxygenase. The exception is Y24, which forms a transient ligand interaction at the dioxygen binding site of Fe2. Site-directed mutagenesis and kinetic analysis with substrate analogs revealed the roles of key active site residues. A fifth histidine that is conserved in the PhnZ subclade, H62, specifically interacts with the substrate 1-hydroxyl. The structures also revealed that Y24 and E27 mediate a unique induced-fit mechanism whereby E27 specifically recognizes the 2-amino group of the bound substrate and toggles the release of Y24 from the active site, thereby creating space for molecular oxygen to bind to Fe2. Structural comparisons of PhnZ reveal an evolutionary connection between Fe(II)-dependent hydrolysis of phosphate esters and oxidative carbon-phosphorus or carbon-carbon bond cleavage, thus uniting the diverse chemistries that are found in the HD superfamily.
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http://dx.doi.org/10.1073/pnas.1320039111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3986159PMC
April 2014

Arabidopsis JAGGED links floral organ patterning to tissue growth by repressing Kip-related cell cycle inhibitors.

Proc Natl Acad Sci U S A 2014 Feb 4;111(7):2830-5. Epub 2014 Feb 4.

Cell and Developmental Biology Department, John Innes Centre, Norwich NR4 7UH, United Kingdom.

Plant morphogenesis requires coordinated cytoplasmic growth, oriented cell wall extension, and cell cycle progression, but it is debated which of these processes are primary drivers for tissue growth and directly targeted by developmental genes. Here, we used ChIP high-throughput sequencing combined with transcriptome analysis to identify global target genes of the Arabidopsis transcription factor JAGGED (JAG), which promotes growth of the distal region of floral organs. Consistent with the roles of JAG during organ initiation and subsequent distal organ growth, we found that JAG directly repressed genes involved in meristem development, such as CLAVATA1 and HANABA TARANU, and genes involved in the development of the basal region of shoot organs, such as BLADE ON PETIOLE 2 and the GROWTH REGULATORY FACTOR pathway. At the same time, JAG regulated genes involved in tissue polarity, cell wall modification, and cell cycle progression. In particular, JAG directly repressed KIP RELATED PROTEIN 4 (KRP4) and KRP2, which control the transition to the DNA synthesis phase (S-phase) of the cell cycle. The krp2 and krp4 mutations suppressed jag defects in organ growth and in the morphology of petal epidermal cells, showing that the interaction between JAG and KRP genes is functionally relevant. Our work reveals that JAG is a direct mediator between genetic pathways involved in organ patterning and cellular functions required for tissue growth, and it shows that a regulatory gene shapes plant organs by releasing a constraint on S-phase entry.
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http://dx.doi.org/10.1073/pnas.1320457111DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3932912PMC
February 2014

Determination of absolute configuration of the phosphonic acid moiety of fosfazinomycins.

Org Biomol Chem 2013 Nov;11(42):7420-6

University of Vienna, Institute of Organic Chemistry, Währingerstraße 38, 1090, Vienna, Austria.

Fosfazinomycins A and B produced by Streptomyces lavendofoliae share the same phosphonate moiety with one chiral centre of unknown configuration which was determined by synthesising both enantiomers of 2-hydroxy-2-phosphonoacetic acid methyl ester. A chiral cyclic phosphite was reacted with methyl glyoxylate in a Pudovik reaction to give a pair of diastereomeric α-hydroxyphosphonates, which were separated by HPLC. The configurations at C-2 were assigned on the basis of single crystal X-ray structure analysis. Deprotection of these diastereomers furnished the enantiomeric α-hydroxyphosphonic acids, of which the (S)-configured had the same sign of optical rotation as the phosphonic acid moiety of the two fosfazinomycins.
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http://dx.doi.org/10.1039/c3ob41574kDOI Listing
November 2013

JAGGED controls Arabidopsis petal growth and shape by interacting with a divergent polarity field.

PLoS Biol 2013 30;11(4):e1001550. Epub 2013 Apr 30.

Department of Cell and Developmental Biology, John Innes Centre, Norwich Research Park, Norwich, United Kingdom.

A flowering plant generates many different organs such as leaves, petals, and stamens, each with a particular function and shape. These types of organ are thought to represent variations on a common underlying developmental program. However, it is unclear how this program is modulated under different selective constraints to generate the diversity of forms observed. Here we address this problem by analysing the development of Arabidopsis petals and comparing the results to models of leaf development. We show that petal development involves a divergent polarity field with growth rates perpendicular to local polarity increasing towards the distal end of the petal. The hypothesis is supported by the observed pattern of clones induced at various stages of development and by analysis of polarity markers, which show a divergent pattern. We also show that JAGGED (JAG) has a key role in promoting distal enhancement of growth rates and influences the extent of the divergent polarity field. Furthermore, we reveal links between the polarity field and auxin function: auxin-responsive markers such as DR5 have a broader distribution along the distal petal margin, consistent with the broad distal organiser of polarity, and PETAL LOSS (PTL), which has been implicated in the control of auxin dynamics during petal initiation, is directly repressed by JAG. By comparing these results with those from studies on leaf development, we show how simple modifications of an underlying developmental system may generate distinct forms, providing flexibility for the evolution of different organ functions.
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http://dx.doi.org/10.1371/journal.pbio.1001550DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3641185PMC
October 2013

JAGGED controls growth anisotropyand coordination between cell sizeand cell cycle during plant organogenesis.

Curr Biol 2012 Oct 16;22(19):1739-46. Epub 2012 Aug 16.

Department of Cell and Developmental Biology, John Innes Centre, Norwich Research Park, Norwich NR4 7UH, UK.

Background: In all multicellular organisms, the links between patterning genes, cell growth, cell cycle, cell size homeostasis, and organ growth are poorly understood, partly due to the difficulty of dynamic, 3D analysis of cell behavior in growing organs. A crucial step in plant organogenesis is the emergence of organ primordia from the apical meristems. Here, we combined quantitative, 3D analysis of cell geometry and DNA synthesis to study the role of the transcription factor JAGGED (JAG), which functions at the interface between patterning and primordium growth in Arabidopsis flowers.

Results: The floral meristem showed isotropic growth and tight coordination between cell volume and DNA synthesis. Sepal primordia had accelerated cell division, cell enlargement, anisotropic growth, and decoupling of DNA synthesis from cell volume, with a concomitant increase in cell size heterogeneity. All these changes in growth parameters required JAG and were genetically separable from primordium emergence. Ectopic JAG activity in the meristem promoted entry into S phase at inappropriately small cell volumes, suggesting that JAG can override a cell size checkpoint that operates in the meristem. Consistent with a role in the transition from meristem to primordium identity, JAG directly repressed the meristem regulatory genes BREVIPEDICELLUS and BELL 1 in developing flowers.

Conclusions: We define the cellular basis for the transition from meristem to organ identity and identify JAG as a key regulator of this transition. JAG promotes anisotropic growth and is required for changes in cell size homeostasis associated with accelerated growth and the onset of differentiation in organ primordia.
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http://dx.doi.org/10.1016/j.cub.2012.07.020DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3471073PMC
October 2012