Biology subjects

Scholz, P.

Publications and source records attributed to Scholz, P..

9 recordsLinked to original sources

bioRxiv2026

Nanoscale regulation of ROS signaling at the plasma membrane tunes the plant response to osmotic stress

The spatiotemporal organization of proteins and lipids within membranes is crucial for ensuring proper cellular signaling. While the segregation of proteins and lipids into membrane nanodomains is well established, it remains unclear whether nanodomains can generate gradients of small diffusible molecules. In plants, reactive oxygen species (ROS), especially hydrogen peroxide (H2O2), act as a key signaling molecules in response to environmental stimuli such as osmotic stress. However, how extracellular H2O2 affects intracellular signaling has remained unknown. Here, we show that osmotic stimulation induces the formation of localized, H2O2-rich nano-environments at the cytoplasmic face of the plasma membrane (PM) in Arabidopsis root cells. Using a PM-tethered H2O2 biosensor, we found that these oxidized nanodomains arise from the clustering of RESPIRATORY BURST OXIDASE HOMOLOGs (RBOHs) and RHO OF PLANTS 6 (ROP6), in coordination with aquaporin-mediated H2O2 transport via the PLASMA MEMBRANE INTRINSIC PROTEIN2;7 (PIP2;7). These local redox hotspots at the PM create a feedforward loop in which H2O2 enhances ROP6 nanoclustering thereby amplifying ROS signaling. Disruption of H2O2 production or transport dampens both ROP6 clustering and anisotropic cell expansion, indicating a crucial role for spatially-confined redox signaling in regulating plant growth under osmotic stress. Our findings propose a model in which ROP6/RBOHD-F/PIP2;7 nanodomains function as discrete redox signaling units, redefining ROS signaling at the PM as a structured, signal-specific, and compartmentalized process.

cell biology↗

bioRxiv2025

Arabidopsis root lipid droplets are hubs for membrane homeostasis under heat stress, and triterpenoid synthesis and storage.

O_LIPlant lipid droplets (LDs) and their associated proteins have numerous subcellular and physiological functions. While considerable progress has been made for LDs in many tissues, the function and composition of LDs in roots remains largely unexplored. C_LIO_LIWe investigated the changes of the number of LDs and of the lipidome in heat-stressed Arabidopsis thaliana roots. Furthermore, we isolated root LDs from the Arabidopsis mutant trigalactosyldiacylglycerol 1-1 sugar dependent 1-4 and investigated their proteome and lipidome. C_LIO_LIHeat stress lead to a degradation of membrane lipids and an increase in TAGs and LDs. while, fatty acid SEs decreased, probably acting as precursors for acylated sterol glycosides. A variety of proteins were enriched in root LDs, which are thus far not described as LD proteins. Transient expression of these proteins in many cases confirmed their LD localization, for example of the triterpene biosynthetic enzymes thalianol synthase and marneral synthase. We could furthermore show that the educts and products of these enzymes are enriched in root LDs, too. C_LIO_LIWe conclude that root LDs simultaneously act as a sink and source during heat stress-induced membrane remodeling. Furthermore, root LDs play a pivotal role in triperpene synthesis and storage, thereby highlighting LDs as hubs in specialized metabolism. C_LI

plant biology↗

bioRxiv2024

Axon demyelination and degeneration in a zebrafishspastizin model of hereditary spastic paraplegia

Hereditary spastic paraplegias (HSPs) are a diverse set of neurological disorders characterized by progressive spasticity and weakness in the lower limbs caused by damage to the axons of the corticospinal tract. More than 88 genetic mutations have been associated with HSP, yet the mechanisms underlying these disorders are little understood. We studied the pathogenesis of one form of HSP known as spastic paraplegia 15 (SPG15). This disorder is caused by mutations in the ZFYVE26 gene, which codes for a protein called SPASTIZIN. We show that, in zebrafish, the significant reduction of Spastizin caused degeneration of Mauthner (M)-cells. M-cell degeneration is associated with axon demyelination in the spinal cord and impaired locomotion in the spastizin mutants. Our findings reveal that the mutation not only compromises axonal integrity but also affects the structural molecules of the myelin sheath, laying the foundation for degeneration and advancing our understanding of the intricate mechanisms underlying HSPs.

neuroscience↗

bioRxiv2024

Plasticity of the Arabidopsis leaf lipidome and proteome in response to pathogen infection and heat stress

Plants must cope with a variety of stressors during their life cycle, and the adaptive responses to these environmental cues involve all cellular organelles. Among them, comparatively little is known about the contribution of cytosolic lipid droplets (LDs) and their core set of neutral lipids and associated surface proteins to the rewiring of cellular processes in response to stress. Here, we analyzed the changes that occur in the lipidome and proteome of Arabidopsis leaves after pathogen infection with Botrytis cinerea or Pseudomonas syringae, or after heat stress. Analyses were carried out in wild-type plants and the oil-rich double mutant tgd1-1 sdp1-4 that allowed for an allied study of the LD proteome in stressed leaves. Using liquid chromatography-tandem mass spectrometry-based methods, we show that a hyperaccumulation of the primary LD core lipid triacylglycerol is a general response to stress and that acyl chain and sterol composition are remodeled during cellular adaptation. Likewise, comparative analysis of the LD protein composition in stress-treated leaves highlighted the plasticity of the LD proteome as part of the general stress response. We further identified at least two additional LD-associated proteins, whose localization to LDs in leaves was confirmed by confocal microscopy of fluorescent protein fusions. Taken together, these results highlight LDs as dynamic contributors to the cellular adaptation processes that underlie how plants respond to environmental stress. One sentence summaryBiotic and heat stress strongly alters the lipidome and proteome of Arabidopsis leaves including the proteome of lipid droplets.

plant biology↗

bioRxiv2022

Environmental gradients reveal stress hubs predating plant terrestrialization

Plant terrestrialization brought forth the land plants (embryophytes). Embryophytes account for most of the biomass on land and evolved from streptophyte algae in a singular event. Recent advances have unraveled the first full genomes of the closest algal relatives of land plants; among the first such species was Mesotaenium endlicherianum. Here, we used fine-combed RNAseq in tandem with photophysiological assessment on Mesotaenium exposed to a continuous range of temperature and light cues. Our data establish a grid of 42 different conditions, resulting in 128 transcriptomes and ~1.5 Tbp (~9.9 billion reads) of data to study combinatory effects of stress response using clustering along gradients. We describe major hubs in genetic networks underpinning stress response and acclimation in the molecular physiology of Mesotaenium. Our data suggest that lipid droplet formation, plastid and cell wall-derived signals denominate molecular programs since more than 600 million years of streptophyte evolution--before plants made their first steps on land.

evolutionary biology↗

bioRxiv2022

SLDP and LIPA mediate lipid droplet-plasma membrane tethering in Arabidopsis thaliana

Membrane contact sites (MCS) are inter-organellar connections that allow for the direct exchange of molecules, such as lipids or Ca2+ between organelles, but can also serve to tether organelles at specific locations within cells. Here we identified and characterised three proteins that form a lipid droplet (LD)-plasma membrane (PM) tethering complex in plant cells, namely LD-localised SEED LD PROTEIN (SLDP) 1 and 2 and PM-localised LD-PLASMA MEMBRANE ADAPTOR (LIPA). Using proteomics and different protein-protein interaction assays, we show that both SLDPs associate with LIPA. Disruption of either SLDP1 and 2 expression, or that of LIPA, leads to an aberrant clustering of LDs in Arabidopsis seedlings. Ectopic co-expression of one of the SLDPs with LIPA on the other hand is sufficient to reconstitute LD-PM tethering in Nicotiana tabacum pollen tubes, a cell type characterised by dynamically moving LDs in the cytosolic streaming. Further, confocal laser scanning microscopy revealed both SLDP2.1 and LIPA to be enriched at LD-PM contact sites in seedlings. These and other results suggest that SLDP and LIPA interact to form a tethering complex that anchors a subset of LDs to the PM during post-germinative seedling growth in Arabidopsis thaliana. One-sentence summarySEED LIPID DROPLET PROTEIN1 and 2 and LIPID DROPLET PLASMA MEMBRANE ADAPTOR tether lipid droplets to the plasma membrane in seedlings of Arabidopsis thaliana.

plant biology↗

bioRxiv2021

Heat stress leads to rapid lipid remodelling and transcriptional adaptations in Nicotiana tabacum pollen tubes

After reaching the stigma, pollen grains germinate and form a pollen tube that transports the sperm cells to the ovule. Due to selection pressure between pollen tubes, they likely evolved mechanisms to quickly adapt to temperature changes to sustain an elongation at the highest possible rate. We investigated these adaptions in Nicotiana tabacum pollen tubes grown in vitro under 22 {degrees}C and 37 {degrees}C by a multi-omic approach including lipidomic, metabolomic and transcriptomic analysis. Both glycerophospholipids and galactoglycerolipids increased in saturated acyl chains under heat stress while triacylglycerols changed less in respect to desaturation but showed higher levels. Free sterol composition was altered, and sterol ester levels decreased. The levels of sterylglycosides and several sphingolipid classes and species were augmented. Most amino acids increased during heat stress, including the non-codogenic amino acids {gamma}-amino butyrate and pipecolate. Furthermore, the sugars sedoheptulose and sucrose showed higher levels. Also the transcriptome underwent pronounced changes with 1,570 of 24,013 genes being differentially up- and 813 being downregulated. Transcripts coding for heat shock proteins and many transcriptional regulators were most strongly upregulated, but also transcripts that have so far not been linked to heat stress. Transcripts involved in triacylglycerol synthesis were increased, while the modulation of acyl chain desaturation seemed not to be transcriptionally controlled indicating other means of regulation. One sentence summaryNicotiana tabacum pollen tubes react to heat stress with metabolomic adaptations, transcriptional adjustments, and a rapid and reversible lipid remodelling.

plant biology↗

bioRxiv2021

Neuronal cholesterol synthesis is essential for repair of chronically demyelinated lesions in mice

Astrocyte-derived cholesterol supports brain cells under physiological conditions. However, in demyelinating lesions, astrocytes downregulate cholesterol synthesis and the cholesterol that is essential for remyelination has to originate from other cellular sources. Here, we show that repair following acute versus chronic demyelination involves distinct processes. In particular, we found that in chronic myelin disease, when recycling of lipids is often defective, de novo neuronal cholesterol synthesis is critical for regeneration. By gene expression profiling, genetic loss of function experiments and comprehensive phenotyping, we provide evidence that neurons increase cholesterol synthesis in chronic myelin disease models and MS patients. In mouse models, neuronal cholesterol facilitated remyelination specifically by triggering OPC proliferation. Our data contribute to the understanding of disease progression and have implications for therapeutic strategies in MS patients.

neuroscience↗

bioRxiv2019

The cell-wall-localised BETA-XYLOSIDASE 4 contributes to immunity of Arabidopsis against Botrytis cinerea

Plant cell walls constitute physical barriers that restrict access of microbial pathogens to the contents of plant cells. The primary cell wall of multicellular plants predominantly consists of cellulose, hemicellulose and pectin. In Arabidopsis, a cell wall-localised protein, BETA-XYLOSIDASE 4 (BXL4) that belongs to a seven-member BETA-XYLOSIDASE (BXL) gene family was induced upon infection with the necrotrophic fungal pathogen Botrytis cinerea and mechanical wounding in a jasmonoyl isoleucine (JA-Ile) dependent manner. Ectopic expression of the BXL4 gene in Arabidopsis seed coat epidermal cells was able to rescue a bxl1 mutant phenotype suggesting that like BXL1, BXL4, had both xylosidase and arabinosidase activity and acts in mura on cell wall polysaccharides. bxl4 mutants show a compromised resistance to B. cinerea. Upon infection, bxl4 mutants accumulated reduced levels of JA-Ile and camalexin. Conditional overexpression of BXL4 resulted in enhanced expression of PDF1.2 and PAD3 transcripts both before and after B. cinerea infection. This was associated with reduced susceptibility of the transgenic lines to B. cinerea. These data suggest that remodelling or degradation of one or more cell wall polysaccharides is important for plant immunity against B. cinerea and plays a role in pathogen-induced JA-Ile and camalexin accumulation. One-sentence summaryBXL4 is a putative bifunctional xylosidase/arabinofuranisodase localising to the apoplast, important for immunity against the necrotrphic pathogen B. cinerea.

plant biology↗