Michael Hothorn

Michael Hothorn
University of Geneva | UNIGE · Department of Botany and Plant Biology

Professor

About

101
Publications
16,473
Reads
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5,557
Citations
Citations since 2016
66 Research Items
3671 Citations
20162017201820192020202120220200400600
20162017201820192020202120220200400600
20162017201820192020202120220200400600
20162017201820192020202120220200400600
Additional affiliations
September 2014 - present
University of Geneva
Position
  • Professor (Associate)
September 2011 - September 2014
Friedrich Miescher Laboratory of the Max Planck Society
Position
  • Independent Max Planck Research Group Leader
June 2007 - August 2011
Salk Institute for Biological Studies
Position
  • PostDoc Position
Education
October 2002 - May 2006
European Molecular Biology Laboratory
Field of study
  • Structural Biology

Publications

Publications (101)
Article
Full-text available
Steroid Receptor Signaling Plant brassinosteroids signal to diverse pathways in plant physiology. These steroid hormones are perceived at the cell surface, where they bind to the receptor BRASSINOSTEROID INSENSITIVE 1 (BRI1). Santiago et al. (p. 889 , published online 8 August) now show that somatic embryogenesis receptor kinase 1 (SERK1) complexes...
Article
Full-text available
Phosphorus is a macronutrient taken up by cells as inorganic phosphate (Pi). How cells sense cellular Pilevels is poorly characterized. Here we report that SPX domains, which are found in eukaryotic phosphate transporters, signaling proteins and inorganic polyphosphate polymerases, provide a basic binding surface for inositol polyphosphate signalin...
Article
Full-text available
Receptor kinases with extracellular leucine-rich repeat domains (LRR-RKs) form the largest group of membrane signaling proteins in plants. LRR-RKs can sense small molecule, peptide, or protein ligands, and may be activated by ligand-induced interaction with a shape complementary SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE (SERK) co-receptor kinase....
Article
Full-text available
Plants use leucine-rich repeat receptor kinases (LRR-RKs) to sense sequence diverse peptide hormones at the cell surface. A 3.0-Å crystal structure of the LRR-RK GSO1/SGN3 regulating Casparian strip formation in the endodermis reveals a large spiral-shaped ectodomain. The domain provides a binding platform for 21 amino acid CIF peptide ligands, whi...
Article
Full-text available
Many eukaryotic proteins regulating phosphate (Pi) homeostasis contain SPX domains that are receptors for inositol pyrophosphates (PP-InsP), suggesting that PP-InsPs may regulate Pi homeostasis. Here we report that deletion of two diphosphoinositol pentakisphosphate kinases VIH1/2 impairs plant growth and leads to constitutive Pi starvation respons...
Article
Full-text available
Triphosphate tunnel metalloenzymes (TTMs) are found in all biological kingdoms and have been characterized in microorganisms and animals. Members of the TTM family have divergent biological functions and act on a range of triphosphorylated substrates (RNA, thiamine triphosphate, inorganic polyphosphate). TTMs in plants have received considerably le...
Preprint
The brassinosteroid (BR) hormone and its plasma membrane receptor BR INSENSITIVE1 (BRI1) is one of the best-studied receptor-ligand pairs for understanding the interplay between receptor endocytosis and signaling in plants. BR signaling is mainly determined by the plasma membrane pool of BRI1, whereas BRI1 endocytosis ensures signal attenuation. Si...
Article
Full-text available
Phosphate (Pi) starvation response (PHR) transcription factors play key roles in plant Pi homeostasis maintenance. They are negatively regulated by stand-alone SPX proteins, cellular receptors for inositol pyrophosphate (PP-InsP) nutrient messengers. How PP-InsP-bound SPX interacts with PHRs is poorly understood. Here, we report crystal structures...
Preprint
Full-text available
Triphosphate tunnel metalloenzymes (TTMs) are found in all biological kingdoms and have been characterized in microorganisms and animals. Members of the TTM family already characterized have divergent biological functions and act on a range of triphosphorylated substrates (RNA, thiamine tri-phosphate, inorganic polyphosphate). TTM proteins in plant...
Article
Full-text available
Inositol pyrophosphates (PP-InsPs) are highly phosphorylated molecules that have emerged as central nutrient messengers in eukaryotic organisms. They can bind to structurally diverse target proteins to regulate biological functions, such as protein–protein interactions. PP-InsPs are strongly negatively charged and interact with highly basic surface...
Preprint
Full-text available
Phosphate (Pi) is a key macronutrient limiting plant growth and crop productivity. In response to the nutrient deficiency, Pi starvation response (PHR) transcription factors activate Pi starvation induced (PSI) genes. PHR transcription factors are negatively regulated by stand-alone SPX proteins, cellular receptors for inositol pyrophosphate (PP-In...
Article
Immune systems respond to "non-self" molecules termed microbe-associated molecular patterns (MAMPs). Microbial genes encoding MAMPs have adaptive functions and are thus evolutionarily conserved. In the presence of a host, these genes are maladaptive and drive antagonistic pleiotropy (AP) because they promote microbe elimination by activating immune...
Article
Full-text available
Significance Coping with UV-B is crucial for plant survival in sunlight. The UV-B photoreceptor UVR8 regulates gene expression associated with photomorphogenesis, acclimation, and UV-B stress tolerance. UV-B photon reception by UVR8 homodimers results in monomerization, followed by interaction with the key signaling protein COP1. We have discovered...
Article
Full-text available
Phosphorus is an essential nutrient taken up by organisms in the form of inorganic phosphate (Pi). Eukaryotes have evolved sophisticated Pi sensing and signaling cascades, enabling them to stably maintain cellular Pi concentrations. Pi homeostasis is regulated by inositol pyrophosphate signaling molecules (PP-InsPs), which are sensed by SPX domain-...
Article
Full-text available
Significance Proper elaboration of the plant body plan requires that cell division patterns are coordinated during development in complex tissues. Activation of cell cycle machinery is critical for this process, but it is not clear how or if this links to cell-to-cell communication networks that are important during development. Here we show that k...
Article
Shade caused by the proximity of neighboring vegetation triggers a set of acclimation responses to either avoid or tolerate shade. Comparative analyses between the shade‐avoider Arabidopsis thaliana and the shade‐tolerant Cardamine hirsuta revealed a role for the atypical basic‐helix‐loop‐helix LONG HYPOCOTYL IN FR 1 (HFR1) in maintaining the shade...
Preprint
Full-text available
Plant-unique receptor kinases harbor conserved cytoplasmic kinase domains and sequence-diverse ectodomains. Here we report crystal structures of CRINKLY4-type ectodomains from Arabidopsis ACR4 and Physcomitrella patens PpCR4 at 1.95 Å and 2.70 Å resolution, respectively. Monomeric CRINKLY4 ectodomains harbor a N-terminal WD40 domain and a cysteine-...
Preprint
Full-text available
The plant UV-B photoreceptor UVR8 plays an important role in UV-B acclimation and survival. UV-B absorption by homodimeric UVR8 induces its monomerization and interaction with the E3 ubiquitin ligase COP1, leading ultimately to gene expression changes. UVR8 is inactivated through redimerization, facilitated by RUP1 and RUP2. Here, we describe a nov...
Preprint
Full-text available
Receptor kinases with extracellular leucine-rich repeat domains (LRR-RKs) form the largest group of membrane signaling proteins in plants. LRR-RKs can sense small molecule, peptide or protein ligands, and may be activated by ligand-induced interaction with a shape complementary SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE (SERK) co-receptor kinase. W...
Article
Filling in the gaps In a plant seed, the embryo lies dormant surrounded by nutritive endosperm while awaiting suitable conditions to germinate. A hydrophobic cuticle around the embryo protects it from catastrophic water loss during the early days of growth. Doll et al. identified a back-and-forth signaling pathway that ensures an intact cuticle. Th...
Preprint
Full-text available
Phosphorus is an essential nutrient taken up by organisms in the form of inorganic phosphate (Pi). Eukaryotes have evolved sophisticated Pi sensing and signalling cascades, enabling them to maintain cellular Pi concentrations. Pi homeostasis is regulated by inositol pyrophosphate signalling molecules (PP-InsPs), which are sensed by SPX-domain conta...
Article
Full-text available
Inorganic polyphosphates (polyPs) are linear polymers of orthophosphate units linked by phosphoanhydride bonds. PolyPs represent important stores of phosphate and energy, and are abundantly found in many pro‐ and eukaryotic organisms. In plants, the existence of polyPs has been established using microscopy and biochemical extraction methods that ar...
Preprint
Full-text available
The plant embryonic cuticle is a hydrophobic barrier deposited de novo by the embryo during seed development. At germination it protects the seedling from water loss and is thus critical for survival. Embryonic cuticle formation is controlled by a signaling pathway involving the protease ALE1 and the receptor-like kinases GSO1 and GSO2. We show tha...
Article
Full-text available
Inorganic polyphosphates (polyPs) and inositol pyrophosphates (PP‐InsPs) form important stores of inorganic phosphate and can act as energy metabolites and signaling molecules. Here we review our current understanding of polyP and InsP metabolism and physiology in plants. We outline methods for polyP and InsP detection, discuss the known plant enzy...
Article
Full-text available
Plants sense different parts of the sun's light spectrum using distinct photoreceptors, which signal through the E3 ubiquitin ligase COP1. Here, we analyze why many COP1-interacting transcription factors and photoreceptors harbor sequence-divergent Val-Pro (VP) motifs that bind COP1 with different binding affinities. Crystal structures of the VP mo...
Preprint
Full-text available
Plants use leucine-rich repeat receptor kinases (LRR-RKs) to sense sequence diverse peptide hormones at the cell surface. A 3.0 Å crystal structure of the LRR-RK GSO1/SGN3 regulating Casparian strip formation in the endodermis reveals a large spiral-shaped ectodomain. The domain provides a binding platform for 21 amino-acid CIF peptide ligands, whi...
Article
Full-text available
Inorganic polyphosphates (polyPs) are linear polymers of orthophosphate units linked by phosphoanhydride bonds. Here, we report that bacterial, archaeal, and eukaryotic conserved histidine α-helical (CHAD) domains are specific polyP-binding modules. Crystal structures reveal that CHAD domains are formed by two four-helix bundles, giving rise to a c...
Preprint
Full-text available
Inorganic polyphosphates (polyPs) are linear polymers of orthophosphate units linked by phosphoanhydride bonds. PolyPs represent important stores of phosphate and energy, and are abundantly found in many pro- and eukaryotic organisms. In plants, the existence of polyPs has been established using microscopy and biochemical extraction methods that ar...
Article
Full-text available
Plant-unique membrane receptor kinases with leucine-rich repeat (LRR) extracellular domains are key regulators of development and immune responses. Here, the 1.55 Å resolution crystal structure of the immune receptor kinase SOBIR1 from Arabidopsis is presented. The ectodomain structure reveals the presence of five LRRs sandwiched between noncanonic...
Article
Pseudoenzymes have burst into the limelight recently as they provide another dimension to regulation of cellular protein activity. In the eudicot plant lineage, the pseudoenzyme PDX1.2 and its cognate enzyme PDX1.3 interact to regulate vitamin B 6 biosynthesis. This partnership is important for plant fitness during environmental stress, in particul...
Preprint
Full-text available
Plant unique membrane receptor kinases with leucine-rich repeat (LRR) extracellular domains are key regulators of development and immune responses. Here we present the 1.55 Å resolution crystal structure of the immune receptor kinase SOBIR1 from Arabidopsis. The ectodomain structure reveals the presence of 5 LRRs sandwiched between non-canonical ca...
Preprint
Full-text available
Plants sense different parts of the sun's light spectrum using specialized photoreceptors, many of which signal through the E3 ubiquitin ligase COP1. Photoreceptor binding modulates COP1's ubiquitin ligase activity towards transcription factors. Here we analyze why many COP1-interacting transcription factors and photoreceptors harbor sequence-diver...
Preprint
Full-text available
Inorganic polyphosphates (polyPs) are long polymers of orthophosphate units (P i ), linked by energy-rich phosphoanhydride bonds. Conserved histidine α-helical (CHAD) domains of unknown biochemical function are often located at the C-terminus of polyP-metabolizing triphosphate tunnel metalloenzymes (TTMs), or can be found as stand-alone proteins in...
Article
Full-text available
Large protein families are a prominent feature of plant genomes and their size variation is a key element for adaptation. However, gene and genome duplications pose difficulties for functional characterization and translational research. Here we infer the evolutionary history of the DOMAIN OF UNKNOWN FUNCTION (DUF) 26-containing proteins. The DUF26...
Article
Full-text available
Eukaryotic mRNAs frequently contain upstream open reading frames (uORFs), encoding small peptides that may control translation of the main ORF (mORF). Here, we report the characterization of a distinct bicistronic transcript in Arabidopsis. We analysed loss-of-function phenotypes of the inorganic polyphosphatase TRIPHOSPHATE TUNNEL METALLOENZYME 3...
Article
The plant embryonic cuticle is a hydrophobic barrier deposited de novo by the embryo during seed development. At germination it protects the seedling from water loss and is thus critical for survival. Embryonic cuticle formation is controlled by a signaling pathway involving the protease ALE1 and the receptor-like kinases GSO1 and GSO2. We show tha...
Preprint
Full-text available
Large protein families are a prominent feature of plant genomes and their size variation is a key element for adaptation in plants. Here we infer the evolutionary history of a representative protein family, the DOMAIN OF UNKNOWN FUNCTION (DUF) 26-containing proteins. The DUF26 first appeared in secreted proteins. Domain duplications and rearrangeme...
Preprint
Full-text available
Many eukaryotic proteins regulating phosphate (Pi) homeostasis contain SPX domains. We have previously shown that these domains act as cellular receptors for inositol pyrophosphate (PP-InsP) signaling molecules, suggesting that PP-InsPs may regulate Pi homeostasis. Here we report that simultaneous deletion of two diphosphoinositol pentakisphosphate...
Article
MacroH2A histone variants suppress tumor progression and act as epigenetic barriers to induced pluripotency. How they impart their influence on chromatin plasticity is not well understood. Here, we analyze how the different domains of macroH2A proteins contribute to chromatin structure and dynamics. By solving the crystal structure of the macrodoma...
Article
Full-text available
In the version of this Letter originally published, there were errors in the x axis labels of Figs 1, 2 and 4: in Fig. 1b, the label Col-0 should not have been included on the axis; in Fig. 2b BIR should have read BIR2, and DN221 should have read D122N; in Fig. 4f, pSEK3 should have read pSERK3. These figures have now been amended in all versions o...
Chapter
Full-text available
Brassinosteroids (BRs) are a class of growth-promoting steroid hormones in plants, which are sensed by the membrane receptor kinase BRASSINOSTEROID INSENSITIVE 1 (BRI1). BR binding to the extracellular domain of BRI1 creates a docking platform for shape-complementary co-receptor kinases of the SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE (SERK) famil...
Article
Full-text available
The leucine-rich repeat receptor kinase (LRR-RK) BRASSINOSTEROID INSENSITIVE 1 (BRI1) requires a shape-complementary SOMATIC EMBRYOGENESIS RECEPTOR KINASE (SERK) co-receptor for brassinosteroid sensing and receptor activation 1 . Interface mutations that weaken the interaction between receptor and co-receptor in vitro reduce brassinosteroid signall...
Article
Full-text available
CLAVATA3/EMBRYO SURROUNDING REGION (CLE) peptides are secreted endogenous plant ligands that are sensed by receptor kinases (RKs) to convey environmental and developmental inputs. Typically, this involves an RK with narrow ligand specificity that signals together with a more promiscuous co-receptor. For most CLEs, biologically relevant (co-)recepto...
Article
Full-text available
Significance Plants contain a unique family of membrane receptors, which are different from the ones found in bacteria and animals. These proteins are able to sense very different signals, such as steroid molecules, peptides, and proteins at the cell surface using a spiral-shaped ligand binding domain. Ligand binding allows the receptor to engage w...
Preprint
Full-text available
The leucine-rich repeat receptor kinase (LRR-RK) BRI1 requires a shape-complementary SERK co-receptor for brassinosteroid sensing and receptor activation. Interface mutations that weaken the interaction between receptor and co-receptor in vitro reduce brassinosteroid signaling responses. The SERK3 elongated ( elg ) allele maps to the complex interf...
Article
Full-text available
Arabidopsis root development is orchestrated by signaling pathways that consist of different CLAVATA3/EMBRYO SURROUNDING REGION (CLE) peptide ligands and their cognate CLAVATA (CLV) and BARELY ANY MERISTEM (BAM) receptors. How and where different CLE peptides trigger specific morphological or physiological changes in the root is poorly understood....
Article
Full-text available
Plants have evolved a family of unique membrane receptor kinases to orchestrate the growth and development of their cells, tissues, and organs. Receptor kinases also form the first line of defense of the plant immune system and allow plants to engage in symbiotic interactions. Here, we discuss recent advances in understanding, at the molecular leve...