Biology subjects

Gutjahr, C.

Publications and source records attributed to Gutjahr, C..

16 recordsLinked to original sources

bioRxiv2026

Karrikin and strigolactone signalling affect pattern-triggered immunity and resistance to specific pathogens

Hormone signalling is important for plant adaptation to biotic stress. Karrikins (KARs), smoke-derived compounds, and strigolactones (SLs), endogenous plant hormones, are families of butenolide mole-cules, sharing a convergent perception and signalling pathway to regulate a plethora of developmental processes and plant-symbiont relationships. Perception of KARs and SLs is mediated by the /{beta}-hydro-lase KARRIKIN INSENSITIVE 2 (KAI2) and DWARF14 (D14), respectively, each resulting in the for-mation of an E3 ubiquitin ligase complex with the F-Box protein MORE AXILLIARY GROWTH 2 (MAX2) to target transcriptional repressors of the SUPPRESSOR OF MAX2 (SMAX)/SMAX-LIKE (SMXL) family for degradation. Most likely, KAI2 additionally perceives a still elusive endogenous ligand (KAI2-ligand, KL). Recent reports suggest a role of KL/SL signalling in plant immunity, but how these pathways are involved in defence, while balancing appropriate symbiont interactions remains largely unknown. Here, we report that KL and SL signalling quantitatively modulate plant immune responses and pathogen re-sistance. In Arabidopsis thaliana (hereafter Arabidopsis), disrupting or de-repressing KL or SL signalling affects plant susceptibility to a variety of plant pathogens. Furthermore, we describe a previously un-known role for KL and SL signalling in modulating pattern-triggered immunity (PTI). Interfering with KL and SL perception in Arabidopsis had similar effects on microbe-associated molecular pattern (MAMP)-triggered reactive oxygen species production, but transcriptomic profiling suggests a predominant role for KL signalling in regulating the extent of PTI. Importantly, KAI2- and D14-mediated regulation of MAMP-triggered ROS production extends to Lotus japonicus and, in the case of KAI2, to Nicotiana benthamiana, indicating conserved immuno-modulatory roles across dicotyledonous lineages. Together our data identify KL and SL signalling, with a predominant role for the KL pathway, as a conserved modulatory layer of plant immunity and provides a framework for understanding how developmental pathways intersect with immune regulation.

plant biology↗

bioRxiv2026

Unequal requirement of KAI2 for AM symbiosis across angiosperms

Development of arbuscular mycorrhiza (AM), a symbiosis between plants and beneficial Glomeromycotan fungi, is largely under plant control. Several genes, required for AM development, are proposed to be regulated by the karrikin signalling module, comprising the alpha/beta hydrolase receptor KARRIKIN INSENSITIVE 2 (KAI2), the F-box protein MORE AXILLARY GROWTH2 (MAX2) and the transcriptional repressor SUPPRESSOR OF MAX2 1 (SMAX1), which is ubiquitylated for proteasomal degradation upon KAI2-ligand-induced binding to the KAI2-MAX2 complex. Rice and Brachypodium distachyon kai2 mutants are incapable of forming AM. Here, we show that in Lotus japonicus, Pisum sativum, and Nicotiana benthamiana, KAI2 only quantitatively affects AM development, indicating angiosperms vary in their requirement for KAI2-signalling to support AM. Comparative transcriptomics of L. japonicus and B. distachyon roots after treatment with fungal signalling molecules revealed some AM-relevant genes respond KAI2-independently in L. japonicus but not in B. distachyon. Consistently we obtained evidence for low-level degradation of SMAX1 in Ljkai2a,b observed through a ratiometric reporter for the SMAX1 degron (SMAX1D2). Further, we found an unexpected accumulation of SMAX1D2 in in response to AM even in wild type. Together, this suggests an unexpected role of SMAX1 accumulation in AM roots and that in AM symbiosis of L. japonicus, redundant mechanisms drive SMAX1 degradation and gene activation independently of KAI2.

plant biology↗

bioRxiv2026

An ancient cis-element regulates translation of arginine decarboxylase to control downstream polyamine biosynthesis and stress responses

Polyamines (PAs) are ubiquitous metabolites that, despite their simple structure, profoundly influence plant growth, development, and stress adaptation. Their cellular levels are largely determined by arginine decarboxylase (ADC), a key rate-limiting enzyme in their biosynthesis. We previously identified a [~]50 bp GC-rich sequence in the 5' untranslated region (UTR) of plant ADC genes, termed the ADC-box, that is conserved across land plants. Transient reporter assays in tomato, in which ADC upstream regions were decoupled from their native coding sequences and fused to reporter genes, suggested that this element represses translation. However, its function in the native genomic context and its impact on PA homeostasis remain unclear. Here, we combined CRISPR-Cas9 genome editing, metabolite profiling, enzymatic assays, and RNA structure probing to define ADC-box function in tomato and in the seedless land plant Marchantia polymorpha, which retains a conserved [~]20 bp core region. Mutation of the M. polymorpha ADC-box increased ADC activity and altered PA levels, indicating that the ADC-box functions as a conserved translational repressor. In tomato, disruption of the ADC-boxes in SlADC1 and SlADC2 increased ADC activity, demonstrating that the ADC-box acts as a translational repressor in its native context. These ehects were most pronounced under cold stress, when ADC transcript levels increase, suggesting that the ADC-box buhers stress-induced translation. Metabolically, ADC-box disruption led to agmatine accumulation and alterations in upstream intermediates, while downstream PA pools remained largely unchanged. SHAPE analysis revealed that the tomato ADC-box folds into a three-stem RNA structure, with a central stem representing the major inhibitory module. ADC-box mutants displayed altered plant-microbe interactions, with enhanced resistance to Pseudomonas syringae and Tobacco rattle virus, but increased susceptibility to Ralstonia solanacearum and Tomato yellow leaf curl virus. Together, these findings establish the ADC-box as an evolutionarily conserved cis-regulatory element that stabilizes PA homeostasis and modulates plant-microbe interactions.

plant biology↗

bioRxiv2026

Brassinosteroid-regulated transcription factors confer epigenetic changes that repress plant immunity

When organisms encounter pathogens, they rapidly activate complex defense programs to ensure survival. While these immune responses are vital, they often also incur trade-offs, such as reduced growth and development and must therefore be tightly controlled 1,2. In this study, we reveal that the steroid hormones brassinosteroids (BRs) contribute to this control in Arabidopsis thaliana by repressing immunity-related genes. We provide evidence that the BR-regulated basic helix-loop-helix (bHLH) transcription factor CESTA (CES), along with its homologs BR ENHANCED EXPRESSION (BEE)1-3, mediate DNA methylation changes at transposable element (TE)-rich loci containing nucleotide-binding leucine-rich-repeat (NLR)-type receptor genes, including SUPPRESSOR OF NPR1-1 CONSTITUTIVE 1 (SNC1). These CES-induced methylation changes correlate with altered splicing of SNC1 pre-mRNA, a process that requires the BR receptor BRASSINOSTEROID INSENSITIVE 1 (BRI1). In support, we show that CES associates with components of the chromatin remodeling and splicing machinery. Together, our findings reveal a previously unrecognized BR-induced mechanism that modulates the epigenetic and post transcriptional regulation of immune genes, enabling plants to prioritize growth over defense. Significance statementSteroid hormones are powerful regulators of growth but also act as potent suppressors of immunity, with well-established clinical applications, for example in treating autoimmune diseases in humans. In plants, the steroid hormones brassinosteroids (BRs) exert similar effects. Here, we uncover that BR-mediated immune suppression involves DNA methylation changes and alternative splicing of a subset of immune receptor genes, that govern resistance responses mediated by the plant hormone salicylic acid. We provide evidence for a function of specific bHLH transcription factors in this process that link BR signaling to chromatin remodelling and RNA processing. Thereby our study reveals a novel mode of steroid hormone activity in immune repression, which involves epigenetic and posttranscriptional adjustment of immune receptor function.

plant biology↗

bioRxiv2025

Ethylene signal-driven plant-multitrophic synergy boosts crop performance

Efficient nutrient use in agriculture depends on the dynamic interplay between plant roots, soil, and microbial communities. The root-rhizosphere interface is central to nutrient uptake and serves as a key hub for interactions with beneficial microbes. Arbuscular mycorrhizal (AM) fungi, positioned at the nexus between plant roots and soil microbiota, play a critical role in enhancing crop performance under nutrient-limited conditions. In this study, we dissected the genetic and molecular basis of AM fungi-induced lateral root development in maize (Zea mays), focusing on the role of ethylene-responsive transcription factors (ERFs). We identified ERF genes as essential regulators of pericycle cell division, acting downstream of ethylene biosynthesis genes (ACS6 and ACS7) and AM fungal signaling. Our findings reveal that AM fungi promote lateral root initiation by activating ERF expression and reprogramming flavonoid metabolism, particularly reducing the accumulation of flavonols such as kaempferol and quercetin, which otherwise inhibit root development when over-accumulated. Furthermore, we demonstrated that Massilia, a beneficial rhizobacterium, synergizes with AM fungi to enhance lateral root formation by colonizing fungal hyphae, degrading flavonoids, and contributing to auxin production. Together, our results uncover a tripartite signaling network linking ethylene signaling, flavonoid-mediated microbial recruitment, and AM symbiosis. This study highlights ERFs as central integrators of plant-microbe interactions and provides a molecular framework for engineering root architecture and microbiome assembly to improve nutrient acquisition and support sustainable crop productivity.

plant biology↗

bioRxiv2025

Adaptation to a host-associated lifestyle drives convergent loss of flagellar motility in Pseudomonadota

BackgroundHost-associated bacteria must balance the benefits of motility through flagella against the offsets of energetic costs and immune surveillance. Understanding the interplay of evolutionary forces shaping this complex trait can provide insights on the dynamics and extent of within-host adaptations of flagellar assembly. We compared prevalence, redundancy, and homology of 55 known flagellar assembly genes across genomes of free-living and host-associated bacteria from a collection covering the entire Pseudomonadota phylum. ResultsWe show that the isolation of host-associated bacterial populations leads to the erosion of the flagellar regulon, driving widespread flagellum loss across lineages. This gene loss is rarely compensated by horizontal gene transfer. Moreover, host association imposes a diversifying selective pressure that acts unevenly across pathway components, resulting in greater functional heterogeneity than in free-living bacteria. ConclusionsOur results provide valuable insights into the distribution of flagellar genes in the phylum Pseudomonadota and its relation to bacterial lifestyle.

microbiology↗

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

C-terminal conformational changes in SCF-D3/MAX2 ubiquitin ligase are required for KAI2-mediated signaling

Karrikins (KARs) are bioactive molecules derived from burning vegetation. Plants perceive KARs through the /{beta} hydrolase KARRIKIN INSENSITIVE 2 (KAI2) that interacts with the F-box protein ubiquitin ligase MORE AXILLARY GROWTH 2 (MAX2). MAX2 also plays a role in the perception and signal activation by Strigolactone (SL), a phytohormone controlling various developmental processes in plants. SL also acts as a rhizosphere signal to activate arbuscular mycorrhiza fungi that can be exploited by parasitic plants. kai2 knockouts exhibit distinct developmental defects and therefore KAI2 is hypothesized to perceive an unidentified endogenous ligand provisionally termed KAI2-Ligand (KL). Upon KAR/KL perception, the protein complex of KAI2-MAX2 targets SUPPRESSOR OF MAX2-1/2 (SMAX1)/SMXL2 for proteasomal degradation. Despite the identification of the key components KAI2, MAX2, and SMAX1 in KAR/KL signaling, their mode of interaction and regulation remains elusive. Recently, the regulatory function of the conformational switch of MAX2 C-terminal helix (CTH) in SL signaling has been demonstrated however its role in KAR/KL signaling remained unknown. Here we address the function of MAX2-CTH dynamics both in vitro and in planta and show that the central role of CTH is conserved between SL and KAR/KL signaling pathway.

plant biology↗

bioRxiv2022

Parental pericentromeric methylation status drives methylome remodelling and heterosis in epigenetic hybrids

Heterosis is the superior phenotypic performance of F1 hybrids relative to their parents. Although this phenomenon is extensively exploited commercially, its molecular causes remain elusive. A central challenge is to understand how specific features of parental (epi)genomes contribute to the widespread functional remodelling that occurs in hybrids. Using Arabidopsis, we show that differentially methylated regions (DMRs) in parental pericentromeres act as major re-organizers of hybrid methylomes and transcriptomes, even in the absence of genetic variation. We demonstrate that these parental DMRs facilitate methylation changes in the hybrids not only in cis, but also in trans at thousands of target regions throughout the genome. Many of these trans-induced changes facilitate the expression of nearby genes, and are significantly associated with phenotypic heterosis. Our study establishes the epigenetic status of parental pericentromeres as an important predictor of heterosis and elucidates its pleiotropic potential in the functional remodelling of hybrid genomes.

genomics↗

bioRxiv2021

PHOSPHATE STARVATION RESPONSE enables arbuscular mycorrhiza symbiosis

Arbuscular mycorrhiza (AM) is a widespread symbiosis between roots of the majority of land plants and Glomeromycotina fungi. AM is important for ecosystem health and functioning as the fungi critically support plant performance by providing essential mineral nutrients, particularly the poorly accessible phosphate, in exchange for organic carbon. AM fungi colonize the inside of roots and this is promoted at low but inhibited at high plant phosphate status, while the mechanistic basis for this phosphate-dependence remained obscure. Here we demonstrate that a major transcriptional regulator of phosphate starvation responses in rice PHOSPHATE STARVATION RESPONSE 2 (PHR2) regulates AM. Root colonization of phr2 mutants is drastically reduced, and PHR2 is required for root colonization, mycorrhizal phosphate uptake, and yield increase in field soil. PHR2 promotes AM by targeting genes required for pre-contact signaling, root colonization, and AM function. Thus, this important symbiosis is directly wired to the PHR2-controlled plant phosphate starvation response.

plant biology↗

bioRxiv2021

KAI2 regulates seedling development by mediating light-induced remodelling of auxin transport

The photomorphogenic remodelling of seedling growth upon exposure to light is a key developmental transition in the plant life cycle. The /{beta}-hydrolase signalling protein KARRIKIN-INSENSITIVE2 (KAI2), a close homologue of the strigolactone receptor DWARF14 (D14), is involved in this process, and kai2 mutants have strongly altered seedling growth as a result1. KAI2 and D14 both act through the MAX2 (MORE AXILLARY BRANCHING2) F-box protein to target proteins of the SMAX1-LIKE (SUPPRESSOR OF MAX2 1) (SMXL) family for degradation, but the signalling events downstream of this step are unclear in both pathways2. Here, we show that kai2 phenotypes arise because of a failure to downregulate auxin transport from the seedling shoot apex towards the root system, rather than a failure to respond to light per se. We demonstrate that KAI2 controls the light-induced remodelling of the PIN-mediated auxin transport system in seedlings, promoting the reduction of PIN3, PIN4, and PIN7 abundance in older tissues, and the increase of PIN1, PIN2, PIN3, and PIN7 abundance in the root meristem, consistent with transition from elongation-mediated growth in the dark to meristematically-mediated growth in the light. We show that removing PIN3, PIN4 and PIN7 from kai2 mutants, or pharmacological inhibition of auxin transport and synthesis, is sufficient to suppress most kai2 seedling phenotypes. KAI2 is not required for the light-mediated changes in PIN gene expression but is required for the changes in PIN protein abundance at the plasma membrane; we thus propose that KAI2 acts to promote vesicle trafficking, consistent with previous suggestions about D14-mediated signalling in the shoot3.

plant biology↗

bioRxiv2021

Acidovorax pan-genome reveals specific functional traits for plant beneficial and pathogenic plant-associations

Beta-proteobacteria belonging to the genus Acidovorax have been described from various environments. Many strains can interact with a range of hosts, including humans and plants, forming neutral, beneficial or detrimental associations. In the frame of this study we investigated genomic properties of 52 bacterial strains of the genus Acidovorax, isolated from healthy roots of Lotus japonicus, with the intent of identifying traits important for effective plant-growth promotion. Based on single-strain inoculation bioassays with L. japonicus, performed in a gnotobiotic system, we could distinguish 7 robust plant-growth promoting strains from strains with no significant effects on plant-growth. We could show that the genomes of the two groups differed prominently in protein families linked to sensing and transport of organic acids, production of phytohormones, as well as resistance and production of compounds with antimicrobial properties. In a second step, we compared the genomes of the tested isolates with those of plant pathogens and free-living strains of the genus Acidovorax sourced from public repositories. Our pan-genomics comparison revealed features correlated with commensal and pathogenic lifestyle. We could show that commensals and pathogens differ mostly in their ability to use plant-derived lipids and in the type of secretion-systems being present. Most free-living Acidovorax strains did not harbour any secretion-systems. Overall, our data indicated that Acidovorax strains undergo extensive adaptations to their particular lifestyle by horizontal uptake of novel genetic information and loss of unnecessary genes.

microbiology↗

bioRxiv2019

Duplicated KAI2 receptors with divergent ligand-binding specificities control distinct developmental traits in Lotus japonicus

Karrikins (KARs), smoke-derived butenolides, are perceived by the /{beta}-fold hydrolase KARRIKIN INSENSITIVE2 (KAI2) and are thought to mimic endogenous, yet elusive plant hormones tentatively called KAI2-ligands (KLs). The sensitivity to different karrikin types as well as the number of KAI2 paralogs varies among plant species, suggesting diversification and co-evolution of ligand-receptor relationships. In legumes, which comprise a number of important crops with protein-rich, nutritious seed, KAI2 has duplicated. We report sub-functionalization of KAI2a and KAI2b in the model legume Lotus japonicus and demonstrate that their ability to bind the synthetic ligand GR24ent-5DS differs in vitro as well as in genetic assays in Lotus japonicus and in the heterologous Arabidopsis thaliana background. These differences can be explained by the exchange of a widely conserved phenylalanine in the binding pocket of KAI2a with a tryptophan in KAI2b, which occured independently in KAI2 proteins of several unrelated angiosperms. Furthermore, two polymorphic residues in the binding pocket are conserved across a number of legumes and may contribute to ligand binding preferences. Unexpectedly, L. japonicus responds to diverse synthetic KAI2-ligands in an organ-specific manner. Hypocotyl development responds to KAR1, KAR2 and rac-GR24, while root system development responds only to KAR1. This organ-specificity cannot be explained by receptor-ligand preferences alone, because LjKAI2a is sufficient for karrikin responses in the hypocotyl, while LjKAI2a and LjKAI2b operate redundantly in roots. Our findings open novel research avenues into the evolution and diversity of butenolide ligand-receptor relationships, their ecological significance and the mechanisms controlling diverse developmental responses to different KAI2 ligands.

plant biology↗

bioRxiv2019

KAI2 regulates root and root hair development by modulating auxin distribution

Strigolactones (SLs) are endogenous signalling molecules that play important roles in controlling plant development. SL perception is closely related to that of karrikins, smoke-derived compounds presumed to mimic endogenous signalling molecules (KLs). SLs have been suggested to regulate root development. However, perception of both molecules requires the F-box protein MAX2 and the use of max2 mutants has hampered defining the exact role of SLs in roots. Here we dissect the role of SL and KL signalling in Arabidopsis root development using mutants defective in the /{beta} hydrolase receptors D14 and KAI2, which specifically perceive SLs and KLs, respectively. Both pathways together regulate lateral root density (LRD), but contrary to previous reports, KL signalling alone controls root hair density, root hair length and additionally root skewing, straightness and diameter. Members of the SMXL protein family are downstream targets of SL (SMXL6, 7, 8) and KL (SMAX1, SMXL2) signalling. We identified distinct and overlapping roles of these proteins in the regulation of root development. Both SMAX1/SMXL2 and SMXL6/SMXL7/SMXL8 regulate LRD, confirming that SL and KL signalling act together to regulate this trait, while the KL-signalling specific SMAX1 and SMXL2 regulate all other investigated root traits. Finally, we show that KL signalling regulates root hair development by modulating auxin distribution within the root.

plant biology↗

bioRxiv2017

Root type and soil phosphate determine the taxonomic landscape of colonizing fungi and the transcriptome of field-grown maize roots

Key findingOur data illustrates for the first time that root type identity and phosphate availability determine the community composition of colonizing fungi and shape the transcriptomic response of the maize root system.\n\nSummaryO_LIPlant root systems consist of different root types colonized by a myriad of soil microorganisms including fungi, which influence plant health and performance. The distinct functional and metabolic characteristics of these root types may influence root type inhabiting fungal communities.\nC_LIO_LIWe performed internal transcribed spacer (ITS) DNA profiling to determine the composition of fungal communities in field-grown axial and lateral roots of maize (Zea mays L.) and in response to two different soil phosphate (P) regimes. In parallel, these root types were subjected to transcriptome profiling by RNA-Seq.\nC_LIO_LIWe demonstrated that fungal communities were influenced by soil P levels in a root type-specific manner. Moreover, maize transcriptome sequencing revealed root type-specific shifts in cell wall metabolism and defense gene expression in response to high phosphate. Furthermore, lateral roots specifically accumulated defense related transcripts at high P levels. This observation was correlated with a shift in fungal community composition including a reduction of colonization by arbuscular mycorrhiza fungi as observed in ITS sequence data and microscopic evaluation of root colonization.\nC_LIO_LIOur findings point towards a diversity of functional niches within root systems, which dynamically change in response to soil nutrients. Our study provides new insights for understanding root-microbiota interactions of individual root types to environmental stimuli aiming to improve plant growth and fitness.\nC_LI

microbiology↗

bioRxiv2017

Lipid transfer from plants to arbuscular mycorrhiza fungi

Arbuscular mycorrhiza (AM) symbioses contribute to global carbon cycles as plant hosts divert up to 20% of photosynthate to the obligate biotrophic fungi. Previous studies suggested carbohydrates as the only form of carbon transferred to the fungi. However, de novo fatty acid (FA) synthesis has not been observed in AM fungi in absence of the plant. In a forward genetic approach, we identified two Lotus japonicus mutants defective in AM-specific paralogs of lipid biosynthesis genes (KASI and GPAT6). These mutants perturb fungal development and accumulation of emblematic fungal 16:1{omega}5 FAs. Using isotopolog profiling we demonstrate that 13C patterns of fungal FAs recapitulate those of wild-type hosts, indicating cross-kingdom lipid transfer from plants to fungi. This transfer of labelled FAs was not observed for the AM-specific lipid biosynthesis mutants. Thus, growth and development of beneficial AM fungi is not only fueled by sugars but depends on lipid transfer from plant hosts.

plant biology↗