Biology subjects

Muehlbauer, S.

Publications and source records attributed to Muehlbauer, S..

3 recordsLinked to original sources

bioRxiv2025

The chloroplast ionome shines new light on organellar Fe homeostasis

Annually, chloroplasts fix 258 billion tons of CO2 through photosynthesis. Photosynthesis and other biochemical pathways require specific amounts of metal ions in the organelle. Transport proteins in the plastid inner envelope maintain the organellar ion homeostasis. Despite substantial progress over the last decades, many genes encoding for plastid ion channels and ion carriers or their regulators remain unknown. To fill this knowledge gap, detailed information on the elemental composition of chloroplasts i.e., a plastid ionome, is needed. This will allow to compare mutants of transporter candidates with wild-types. Here, we provide quantitative descriptions of chloroplast ionomes from Arabidopsis thaliana, the metal hyperaccumulator Arabidopsis halleri, Pisum sativum, and Nicotiana benthamiana and analyze similarities and distinctions. Using A. thaliana, we show that plastid ionomes can be genetically manipulated. Chloroplasts of oligopeptide transporter3 (opt3)-deficient mutants contain 14-fold more iron, which they deposit into stromal FERRITIN. The removal of FERRITIN in opt3 mutants leads to a substantial decrease in plastid and leaf iron pointing to important signaling linked to the chloroplast ionome. Our study reveals that chloroplasts can be turned into large iron storages. Since crop biofortification to fight hidden hunger has become a global mission, this research provides groundwork to reach this goal.

plant biology↗

bioRxiv2025

Catch & Release - rapid cost-effective protein purification from plants using a DIY GFP-Trap-protease approach

The purification of proteins is the foundation to study their structure, function, biochemical properties, and interaction partners. In plant research, unique challenges arise from the complexity of plant tissues, interference of secondary metabolites, and sometimes the low abundance of target proteins. Many conventional plant protein purification methods rely on expensive reagents, multi-step procedures, and labor-intensive workflows, limiting their feasibility for many applications. Here, we present the "Catch & Release" system, a cost-effective, fast and reliable one-step purification workflow for the isolation of soluble and membrane-bound proteins from plant tissues. The Catch & Release toolbox includes a vector set, a homemade GFP-trap and homemade proteases. Catch & Release vectors streamline cloning and transgenic plant selection through the Fluorescence-Accumulating Seed Technology (FAST), which marks positive transformants with a strongly fluorescing seed coat. Each plasmid consists of four, easy to exchange, modules: a plant promoter, a cloning dropout marker, protease cleavage sites, and seven different epitope tags, including an innovative dual-fluorescent tag, providing flexibility for diverse experimental needs. The in vivo functionality of all modules has been confirmed. Besides enabling standard molecular biological experimentation, our vector set in combination with homemade GFP-trap and proteases enables efficient and rapid isolation of soluble and high molecular weight membrane proteins directly from plants. By following our detailed reagent preparation instructions, purification costs can be decreased hundred-fold compared to the commercially available options.

plant biology↗

bioRxiv2024

Premature upregulation of miR-92a's target RBFOX2 hijacks PTBP splicing and impairs cortical neuronal differentiation.

Alternative splicing is a crucial component of neuronal differentiation, yet the mechanisms that regulate splicing transitions during embryonic brain development remain incompletely understood. Here, we identify a post-transcriptional mechanism that times the expression of the splicing factor Rbfox2 during neurogenesis. RBFOX2 is normally expressed at low levels in neural progenitor cells (NPCs) and becomes upregulated in newborn neurons where it promotes neuronal differentiation. Unexpectedly, premature expression of Rbfox2 in NPCs of the embryonic mouse neocortex blocked their differentiation into neurons rather than promoting it. Genome-wide analysis revealed widespread alternative splicing changes enriched for NDD genes and associated with a hybrid NPC- and neuron-like splicing pattern that significantly deviates from the normal splicing developmental trajectory. Remarkably, premature Rbfox2 expression induced the inclusion of validated target exons that are otherwise repressed by PTBP2 pointing to an antagonistic splicing relationship. Integrative scRNA-seq analysis confirmed a negatively correlated expression between these two RNA-binding proteins (RBP) along differentiation pseudotime. Strikingly, we identified the NPC-specific miRNA 92a-3p as a regulator of the Rbfox2 expression switch: expression of miR-92a reduced RBFOX2 levels and reversed splicing patterns of target genes in vitro, while silencing miR-92a in vivo increased RBFOX2 expression in the embryonic cortex. Together, these findings reveal a previously unrecognized miRNA-RBP regulatory axis that ensures the proper timing of NPC-to-neuron splicing transitions in the developing cortex and provide new insights into splicing dysregulation as a contributing factor to the emergence of neurodevelopmental disorders. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=152 HEIGHT=200 SRC="FIGDIR/small/614071v3_ufig1.gif" ALT="Figure 1"> View larger version (28K): org.highwire.dtl.DTLVardef@16248caorg.highwire.dtl.DTLVardef@198dd0dorg.highwire.dtl.DTLVardef@d8887aorg.highwire.dtl.DTLVardef@1e8419e_HPS_FORMAT_FIGEXP M_FIG C_FIG Graphical Abstract Schematic representation of the proposed splicing regulation for the transition of undifferentiated NPCs to neurons in the developing cerebral cortex.

genomics↗