Biology subjects

Engelsdorf, T.

Publications and source records attributed to Engelsdorf, T..

14 recordsLinked to original sources

bioRxiv2026

Phytosulfokine signaling modulates salt stress responses and cell wall remodeling in Arabidopsis

Salinity severely impairs plant growth and development. Increasing evidence suggests that the cell wall (CW) plays a central role in salt stress acclimation, not only as a structural barrier but also as a dynamic sensor that activates downstream stress signaling pathways. To identify extracellular factors involved in cell wall remodeling and integrity signaling during salt stress, we performed a comparative proteomic analysis of the Arabidopsis seedling apoplast. Among the proteins that accumulated under salt stress, we focused on three members of the Subtilisin-Like Protease family (SBT1.1, SBT1.6, and SBT5.3), which have previously been implicated in the processing of signaling peptides and CW-associated proteins. Functional analyses revealed that sbt1.1 and sbt5.3 mutants exhibit enhanced lignin deposition under salt stress, suggesting altered CW remodeling during stress application. Given the established role of SBT1.1 in processing PHYTOSULFOKINE (PSK) peptides, we investigated the involvement of PSK signaling in salt stress responses. Mutants lacking the two PSK RECEPTORS (pskr1 pskr2) displayed reduced growth and increased lignification under salt treatment. Exogenous application of PSK attenuated salt-induced responses, including MITOGEN ACTIVATED PROTEIN KINASE 6 (MPK6) phosphorylation, salt stress marker gene expression, and lignin accumulation, ultimately promoting root elongation under salt stress. Furthermore, PSK treatment mitigated salt-induced changes in CW composition. In cell wall integrity (CWI) mutants, PSK treatment failed to restore wild-type root growth under salt stress and induced a pronounced root bending phenotype in fer-4, indicating that CWI signaling influences PSK-mediated root growth responses. Together, these results support a role for PSK signaling in modulating CW-associated responses to salinity stress in Arabidopsis.

plant biology↗

bioRxiv2026

Defining the Xanthomonas euvesicatoria type II-secreted effector arsenal: core nutritional functions and effector diversity

O_LIThe type II secretion (T2S) system is conserved across the Xanthomonas lineage, yet its contributions to pathogenicity and secreted protein repertoires are poorly defined. We demonstrate that T2S systems in Xanthomonas pathovars with divergent hosts and lifestyles are required for disease. C_LIO_LIIn planta quantification of cell wall compositional changes during infection by Xanthomonas euvesicatoria (Xe) revealed that T2S-dependent depletion of galacturonic acid occurs during host colonization, providing experimental evidence for T2 effector (T2E)-mediated cell wall remodeling. C_LIO_LIUsing an in planta label-free proteomics approach, we identified two known and 20 new Xe T2Es from tomato apoplast, many with annotated functions in polysaccharide and protein cleavage. Growth assays on plant cell wall extracts and purified substrates revealed T2S-mediated metabolization of plant cell wall polysaccharides and proteins not only by Xe, but also by Xanthomonas axonopodis pv. glycines (Xag) and Xanthomonas campestris pv. campestris (Xcc). Interestingly, comparative sequence analysis revealed that the T2E repertoires have diversified among these pathogens, with differences in protease repertoire being the most pronounced. C_LIO_LIOur methodology establishes a framework for T2E discovery, enabling future functional dissection of this understudied effector class and its crosstalk with other bacterial virulence factors. C_LI

plant biology↗

bioRxiv2025

Coping with stress: Transcriptional regulators linking cell wall integrity maintenance with primary-wall metabolism in Arabidopsis thaliana

Cell wall damage (CWD) and hyperosmotic stress elicit both distinct and overlapping transcriptional programs in plants. Responses to these stresses involve cell wall integrity (CWI) maintenance, which is mediated by receptor-like kinases such as THESEUS1 (THE1), yet the downstream regulators linking early signalling to primary cell-wall metabolism and stress-induced phytohormone biosynthesis remain poorly defined. We induced CWD and hyperosmotic stress in wild type and the1 mutant alleles with isoxaben (ISX) and sorbitol, and analysed the gene expression of treated seedlings by RNA-seq. From these data, we focused on 15 transcriptional regulators whose expression was responsive to treatments and showed dependency on THE1 activity. Following up, we performed various functional analyses in mutant lines of these candidates and identified transcription factors that influence primary cell-wall metabolism, growth, transcriptional control of cellulose production, resistance to CWD and hyperosmotic stress, as well as phytohormone and lignin biosynthesis. Our results identify JMJ17, bHLH, and CBP60A as essential transcriptional regulators involved in responses to CWD and hyperosmotic stress, and they provide a starting point for dissecting the transcriptional network that regulates CWI maintenance and primary cell wall metabolism. This study sheds light on a previously unknown signalling network that regulates primary cell wall synthesis in control and stress conditions, providing a basis for more resilient crop plant breeding in the future. Significance StatementPlants provide food and materials used by society, and their productivity depends on maintaining cell wall integrity (CWI) during growth, development, and environmental stress. The CWI maintenance mechanism, involving receptor-like kinases such as THESEUS1 (THE1), has been extensively investigated, yet the transcriptional regulators involved in primary wall metabolism and stress-induced phytohormone production remain unknown. Here, we integrate transcriptomics with functional genetic and physiological assays to identify transcription factors acting in a THE1-dependent/independent manner. These regulators link CWI, hyperosmotic stress, and cell wall damage to primary wall metabolism, lignification, phytohormone production, and root growth. Our findings reveal elements of the transcriptional network that coordinate CWI and primary cell wall formation with adaptive responses, generating insights to enhance crop stress resilience.

plant biology↗

bioRxiv2025

Cell wall integrity and elicitor peptide signaling modulate antimicrobial defense in Arabidopsis via jasmonic acid

Plant cell walls constitute dynamic barriers that are essential for defense against pathogens. The receptor kinase THESEUS1 (THE1) monitors cell wall integrity (CWI) and contributes to pathogen resistance in Arabidopsis, but the underlying mechanisms remain unclear. Here we show that THE1-dependent CWI signaling induces accumulation of the antimicrobial metabolite camalexin upon cell wall damage (CWD) caused by cellulose biosynthesis inhibition or fungal infection. CWD alters THE1 plasma membrane nanodomain organization and involves calcium signaling components that modulate camalexin production. Induction of camalexin requires jasmonic acid (JA)-dependent expression of the transcription factors MYB47 and MYB95. In line with its antagonistic function on CWI signaling, the plant elicitor peptide Pep3 suppresses camalexin biosynthesis downstream of THE1 by inhibiting JA-dependent pathways. Our findings reveal a regulatory network where CWI and Pep3 signaling modulate antimicrobial defense via JA-mediated camalexin production. This network requires independent CWD-induced pathways, providing insights into how plants balance defense activation and suppression in response to cell wall stress.

plant biology↗

bioRxiv2025

The evolutionary history of plastid outer envelope proteins - a structure-sequence comparison

Plant metabolism heavily relies on chloroplasts, derived from once free-living organisms. However, how two distinct organisms merged into one remains currently only partially understood. Protein-mediated metabolite exchange across the double-membrane chloroplast envelope is essential for plant cell function. Here, we investigate the evolutionary origins of outer envelope proteins (OEPs) involved in these transport processes. The mosaic nature of the nuclear genome and the deep evolutionary distance since plastid acquisition are major challenges. To address them, we combine sequence-based analyses with emerging structure-based tools, which together enable more sensitive evolutionary comparisons than traditional methods alone. To uncover distinct evolutionary trajectories, we focused on five OEP families: four {beta}-barrel proteins involved in metabolite transport and JASSY, the first published OPDA transporter. We found that the {beta}-barrel proteins were recruited in a stepwise manner and structural homologs of some OEPs point to early recruitment via endosymbiotic gene transfer (EGT). Notably, OEP40 shows a recent structural rearrangement, lacking clear structural homologs in plants other than Arabidopsis, yet retaining sequence conservation across all major land-plant lineages. The JASSY-like family is found across plastid-bearing species, while true JASSY orthologs emerged in embryophytes likely via a stable recruitment of the characteristic lipid-binding domain. Overall, our findings highlight the dynamic nature of the chloroplast outer envelope and show how new functions evolved through structural reshaping and novel domain recruitment. Structure-based approaches thus powerfully complement sequence data, offering more in-depth insight into the evolution of plastid transport systems.

evolutionary biology↗

bioRxiv2025

Galactan mobilization during carbon starvation compromises cell wall-mediated fungal resistance in Arabidopsis

Polysaccharides are the main components present in plant cell walls. They form a network that is dynamically modified during growth and upon both abiotic and biotic stress. We investigated how the cell wall of Arabidopsis rosettes is remodeled during periods of dark-induced starvation in the wild type and in plastidic phosphoglucomutase (pgm) mutants, which suffer from periodic starvation due to starch deficiency. Time-course analysis demonstrated that up to one fifth of the galactose present in leaf cell walls is reversibly released upon starvation, while other cell wall monosaccharides were less affected. An investigation of BETA-GALACTOSIDASE (BGAL) expression and the analysis of bgal mutants indicated that BGAL1 and BGAL4 contribute to the release of cell wall galactose upon starvation. Increased transcript abundance of UDP-GLUCOSE 4-EPIMERASE (UGE) 1 and 3 under starvation proposed an increased flux through the galactose salvage pathway, however an analysis of the UDP- galactose pool in mutant plants indicated redundancy with other UGEs. Simultaneously to galactan degradation, GALACTAN SYNTHASE1 (GALS1) expression was reduced, attenuating the synthesis of new galactan chains. We show that overexpression of GALS1 prevents depletion of the recyclable cell wall galactose pool and is sufficient to rescue impaired penetration resistance to the hemibiotrophic fungal pathogen Colletotrichum higginsianum upon dark-induced and periodic starvation. Our data suggest that pectic galactan in the plant cell wall serves as a sugar resource during starvation conditions. However, galactose release from the wall leads to impaired penetration resistance against a fungal pathogen, causing a tradeoff between sugar supply for plant metabolism and preformed defense. Significance statementPolysaccharides present in plant cell walls must be dynamically modified in response to external stimuli, but it is not well understood how cell wall remodeling is adjusted in response to metabolic cues and how this affects defense against pathogens. Here, we report that galactose is reversibly released from cell walls upon carbon starvation, which critically affects penetration resistance to a fungal pathogen.

plant biology↗

bioRxiv2025

Endogenous RALF peptide function is required for powdery mildew host colonization

The receptor kinase FERONIA (FER) is a susceptibility factor for biotrophic powdery mildew fungal pathogens in Arabidopsis thaliana, but the underlying molecular mechanisms remain largely unknown. FER is required for the perception of endogenous RAPID ALKALINIZATION FACTOR (RALF) peptides to control various aspects of plant growth, development and immunity. RALFs are perceived by FER-LORELEI-LIKE GPI-ANCHORED PROTEIN (LLG) heterocomplexes to induce cellular responses and bind to LEUCINE-RICH REPEAT EXTENSIN (LRX) proteins as structural components of the cell wall. Combining genetics, cell biology and biochemistry, we found that FERs endogenous RALF ligands are necessary for full colonization success of the powdery mildew species Erysiphe cruciferarum. We reveal that LLGs and LRXs are also powdery mildew susceptibility factors. We show that cell wall remodeling and apoplastic pH homeostasis, hallmark features of RALF function, support powdery mildew reproductive success. Moreover, we provide data that RALF-dependent powdery mildew pathogenesis is partially independent of FER. Powdery mildew fungi likely do not produce RALF peptide mimics, suggesting their reliance on endogenous RALFs for successful host colonization. We propose that powdery mildew fungi require RALF-mediated modulation of apoplastic pH and pectin re-modelling for successful host colonization, highlighting a new susceptibility mechanism by obligate biotrophic fungi.

plant biology↗

bioRxiv2025

The Ustilago maydis transcription factor Nit2 controls nitrate assimilation during biotrophy and adjusts organic nitrogen metabolism in maize leaves under N limitation

Little is known on how filamentous phytopathogens adapt to nitrogen limitation in the host plant. In previous work, we have shown that the transcription factor Nit2 plays a major role for the utilization of non-favored nitrogen sources like nitrate, minor amino acids or nucleobases in saprotrophic sporidia of the basidiomycete corn smut fungus Ustilago maydis. Here, we employed{Delta} nit2 mutants in the natural FB1 x FB2 background to identify Nit2 regulated genes during biotrophy and investigated the impact of Nit2 on the physiology of leaf galls in nitrogen replete versus nitrogen limited host plants. RNA-Seq analysis of galls caused by the U. maydis {Delta}nit2 mutant and by the U. maydis wild type, revealed that about one third of the genes affected by Nit2 deletion during fungal biotrophy are involved in nitrogen metabolism and transport. Induction of the nitrate assimilation cluster was completely dependent on Nit2 and under nitrogen limitation,{Delta} nit2 leaf galls accumulated nitrate and showed reduced accumulation of the nitrogen-rich phloem transport amino acids asparagine and glutamine compared to wild type galls. In nitrogen replete conditions, only asparagine content was reduced in{Delta} nit2 leaf galls compared to wild type galls. Since total protein content in galls and pathogenicity were comparable between fungal genotypes in both nitrogen regimes, our findings demonstrate that nitrate utilization is dispensable for Ustilago maydis during biotrophy and can likely be compensated by increased utilization of abundant organic nitrogen sources, like asparagine, GABA and glutamine, which occurs in a partially Nit2-dependent fashion.

plant biology↗

bioRxiv2024

Linear β-1,2-glucans trigger immune hallmarks and disease resistance in plants

Immune responses in plants are triggered by molecular patterns or elicitors, recognized by plant pattern recognition receptors (PRRs). Such molecular patterns arise from host-pathogen interactions and the response cascade activated after their perception is known as pattern-triggered immunity (PTI). Glucans have emerged as key players in PTI, but certain glucans ability to stimulate defensive responses in plants remains understudied. This work focused on identifying novel glucan oligosaccharides acting as molecular patterns. The ability of various microorganism-derived glucans to prompt PTI responses was tested, revealing that specific microbial-derived glucans, such as short linear {beta}-1,2-glucans, trigger this response in plants by increasing reactive oxygen species (ROS) production, MAP kinase phosphorylation, and differential expression of defence-related genes in Arabidopsis thaliana. Pretreatments with {beta}-1,2-glucan trisaccharide (B2G3) improved Arabidopsis defence against bacterial and fungal infections in a hypersusceptible genotype. The knowledge generated was then transferred to the monocotyledonous model species maize and wheat, confirming that these plants also respond to {beta}-1,2-glucans, with increased ROS production and improved protection against fungal infections following B2G3 pretreatments. In summary, as with other {beta}-glucans, plants perceive {beta}-1,2-glucans as warning signals and stimulate defence responses against phytopathogens. HighlightsWe describe a new group of glycans present in the extracellular matrices of some plant-interacting microorganisms that are sensed by host surveillance systems and enhance the plants natural resistance to disease.

plant biology↗

bioRxiv2023

Root branching in salt requires auxin-independent modulation of LBD16 function

Salinity stress constrains lateral root (LR) growth and severely impacts plant growth. Auxin signaling is indispensable for the regulation of LR formation. Nevertheless, the molecular mechanism of how salinity affects root auxin signaling and whether salt would steer alternative pathway(s) to regulate LR development is unknown. Here we show that the auxin-regulated transcription factor LATERAL ORGAN BOUNDARY DOMAIN (LBD)16, known as an essential player for LR development under control conditions, is regulated by an alternative non-canonical pathway under salinity. Salt represses auxin signaling but in parallel activates an upstream transcriptional activator of LBD16, ZINC FINGER OF ARABIDOPSIS THALIANA 6 (ZAT6). ZAT6 modulates the activity of LBD16 to contribute to downstream cell wall remodeling, and promotes LR development under salinity stress. Our study thus shows that root developmental plasticity in response to salt stress is achieved by integration of auxin-dependent repressive and salt-activated auxin-independent pathways converging on LBD16 to modulate root branching modulation under salinity.

plant biology↗

bioRxiv2021

THESEUS1 modulates cell wall stiffness and abscisic acid production in Arabidopsis thaliana

Plant cells can be distinguished from animal cells by their cell walls and high turgor pressure. Although changes in turgor and stiffness of cell walls seem coordinated, we know little about the mechanism responsible for coordination. Evidence has accumulated that plants, like yeast, have a dedicated cell wall integrity maintenance mechanism. This mechanism monitors the functional integrity of the wall and maintains it through adaptive responses when cell wall damage occurs during growth, development, and interactions with the environment. The adaptive responses include osmo-sensitive-induction of phytohormone production, defence responses as well as changes in cell wall composition and structure. Here, we investigate how the cell wall integrity maintenance mechanism coordinates changes in cell wall stiffness and turgor in Arabidopsis thaliana. We show that the production of abscisic acid (ABA), the phytohormone modulating turgor pressure and responses to drought, depends on the presence of a functional cell wall. We find that the cell wall integrity sensor THESEUS1 modulates mechanical properties of walls, turgor loss point and ABA biosynthesis. We identify RECEPTOR-LIKE PROTEIN 12 as a new component of cell wall integrity maintenance controlling cell wall damage-induced jasmonic acid production. Based on the results we propose that THE1 is responsible for coordinating changes in turgor pressure and cell wall stiffness. Significance statementPlants need to constantly adapt to a changing environment. This includes responses to biotic and abiotic stress. Key elements influencing the response to abiotic stress are the plant cell walls surrounding all cells and the phytohormone abscisic acid, which influences turgor pressure in plants. Turgor pressure in plant cells is much higher than in animal cells and a key driver of plant growth and development. Here we investigate the mechanism regulating cell wall stiffness and coordinating changes in stiffness and turgor. We characterize key elements of the mechanism and dissect its mode of action. This knowledge will enable us to pursue novel approaches to improve plant resistance to drought stress, which is crucial in a rapidly changing environment.

plant biology↗

bioRxiv2019

Functional characterization of genes mediating cell wall metabolism and responses to plant cell wall integrity impairment

Plant cell walls participate in all plant-environment interactions. Maintaining cell wall integrity (CWI) during these interactions is essential. This realization led to increased interest in CWI and resulted in knowledge regarding early perception and signalling mechanisms active during CWI maintenance. By contrast, knowledge regarding processes mediating changes in cell wall metabolism upon CWI impairment is very limited. To identify genes involved and to investigate their contributions to the processes we selected 23 genes with altered expression in response to CWI impairment and characterized the impact of T-DNA insertions in these genes on cell wall composition using Fourier-Transform Infrared Spectroscopy (FTIR) in Arabidopsis thaliana seedlings. Insertions in 14 genes led to cell wall phenotypes detectable by FTIR. A detailed analysis of four genes found that their altered expression upon CWI impairment is dependent on THE1 activity, a key component of CWI maintenance. Phenotypic characterizations of insertion lines suggest that the four genes are required for particular aspects of CWI maintenance, cell wall composition or resistance to Plectosphaerella cucumerina infection in adult plants. Taken together, the results implicate the genes in responses to CWI impairment, cell wall metabolism and/or pathogen defence, thus identifying new molecular components and processes relevant for CWI maintenance.

plant biology↗

bioRxiv2018

Cellulose biosynthesis inhibition reduces cell cycle activity in a nitrate reductase- and cytokinin-dependent manner

O_LIDuring growth, development and defense, cell wall integrity needs to be coordinated with cell cycle activity. In Saccharomyces cerevisiae, coordination is mediated by the cell wall integrity maintenance mechanism. In plants, little is known how coordination is achieved.\nC_LIO_LIHere we investigated coordination between plant cell wall and cell cycle activity in Arabidopsis thaliana seedlings by studying the impact of cell wall damage (CWD, caused by cellulose biosynthesis inhibition) on cell cycle gene expression, growth, phytohormone (jasmonic acid, salicylic acid, cytokinins) and lignin accumulation.\nC_LIO_LIWe found root growth and cell cycle gene expression are reduced by CWD in an osmo-sensitive manner. trans-zeatin application suppressed the CWD effect on gene expression. Quantification of cytokinins revealed CWD-induced, osmo-sensitive changes in several cytokinins. Expression of CYTOKININ OXIDASE2/DEHYDROGENASE (CKX2) and CKX3, encoding cytokinin-degrading enzymes, was elevated in CWD-exposed seedlings. Genetic studies implicated NITRATE REDUCTASE1/2 (NIA1/2) in the response to CWD. In nia1/2 seedlings CWD induced neither expression of CKX2/3 and cell cycle genes nor accumulation of jasmonic acid, salicylic acid and lignin.\nC_LIO_LIThis suggests that CWD causes increased CKX2/3 expression through a NIA1/2-mediated process. Increased CKX expression seems to cause changes in cytokinin levels, leading to reduced cell cycle gene expression.\nC_LI

plant biology↗

bioRxiv2017

Pattern-Triggered Immunity And Cell Wall Integrity Maintenance Jointly Modulate Plant Stress Responses

Plant cells are surrounded by walls, which must often meet opposing functional requirements during plant growth and defense. The cells meet them by modifying wall structure and composition in a tightly controlled and adaptive manner. The modifications seem to be mediated by a dedicated cell wall integrity (CWI) maintenance mechanism. Currently the mode of action of the mechanism is not understood and it is unclear how its activity is coordinated with established plant defense signaling. We investigated responses to induced cell wall damage (CWD) impairing CWI and the underlying mechanism in Arabidopsis thaliana. Interestingly inhibitor- and enzyme-derived CWD induced similar, turgor-sensitive stress responses. Genetic analysis showed that the receptor-like kinase (RLK) FEI2 and the mechano-sensitive, plasma membrane-localized Ca2+- channel MCA1 function downstream of the THE1 RLK in CWD perception. Phenotypic clustering with 27 genotypes identified a core group of RLKs and ion channels, required for activation of CWD responses. By contrast, the responses were repressed by pattern-triggered immune (PTI) signaling components including PEPR1 and 2, the receptors for the immune signaling peptide AtPep1. Interestingly AtPep1 application repressed CWD-induced phytohormone accumulation in a PEPR1/2-dependent manner. These results suggest that PTI suppresses CWD-induced defense responses through elicitor peptide-mediated signaling during defense response activation. If PTI is impaired, the suppression of CWD-induced responses is alleviated, thus compensating for defective PTI.\n\nSignificance statementStress resistance and plant growth determine food crop yield and efficiency of bioenergy production from ligno-cellulosic biomass. Plant cell walls are essential elements of the biological processes, therefore functional integrity of the cell walls must be maintained throughout. Here we investigate the plant cell wall integrity maintenance mechanism. We characterize its mode of action, identify essential signaling components and show that the AtPep1 signaling peptide apparently coordinates pattern triggered immunity (PTI) and cell wall integrity maintenance in plants. These results suggest how PTI and cell wall modification coordinately regulate biotic stress responses with plants possibly compensating for PTI impairment through enhanced activation of stress responses regulated by the CWI maintenance mechanism.

plant biology↗