Biology subjects

Trentmann, O.

Publications and source records attributed to Trentmann, O..

4 recordsLinked to original sources

bioRxiv2025

The secreted redox sensor roGFP2-Orp1 reveals oxidative dynamics in the plant apoplast

- Specific generation of reactive oxygen species (ROS) is important for signalling and defence in many organisms. In plants, different types of ROS serve useful biological functions in the extracellular space (apoplast), influencing polymer structures as well as signaling during immune responses. The current knowledge of apoplastic ROS dynamics is limited, as dynamic monitoring of extracellular redox processes in vivo remains difficult. - We employed evolutionary distant land plant model species from bryophytes and flowering plants to test whether the genetically encoded redox biosensor roGFP2-Orp1 can be used to assess extracellular redox dynamics. - Secreted roGFP2-Orp1 can inform about local diffusion barriers and protein cysteinyl oxidation rate in the apoplast, after pre-reduction. Observed re-oxidation rates were slow, within the range of hours. Compared to Physcomitrium patens, re-oxidation in Arabidopsis thaliana was faster and increased after triggering an immune response. Comparing roGFP2-Orp1 signals in tip-growing P. patens protonema and Nicotiana tabacum pollen tubes, we consistently find no intracellular redox gradient, but partially reduced extracellular sensor in pollen tubes. - Our data indicate differences in extracellular oxidative processes between species and within a species, depending on cell type and immune signalling.

plant biology↗

bioRxiv2023

Chloroplasts lacking class I glutaredoxins are functional but show a delayed recovery of protein cysteinyl redox state after oxidative challenge

Redox status of protein cysteinyl residues is mediated via glutathione (GSH)/glutaredoxin (GRX) and thioredoxin (TRX)-dependent redox cascades. An oxidative challenge can induce post-translational protein modifications on thiols, such as protein S-glutathionylation. Class I GRX are small thiol-disulfide oxidoreductases that reversibly catalyse S-glutathionylation and protein disulfide formation. TRX and GSH/GRX redox systems can provide partial backup for each other in several subcellular compartments, but not in the plastid stroma where TRX/light-dependent redox regulation of primary metabolism takes place. While the stromal TRX system has been studied at detail, the role of class I GRX on plastid redox processes in vivo is still unknown. We generate knockout lines of GRXC5 as the only chloroplast class I GRX of the moss Physcomitrium patens. While we find that class I PpGRXC5 has high activities in glutathione-dependent oxidoreductase assays using hydroxyethyl disulfide or redox-sensitive GFP2 (roGFP2) as substrates in vitro, {Delta}grxc5 plants show no detectable growth defect or stress sensitivity, in contrast to mutants with a less negative stromal EGSH ({Delta}gr1). Using stroma-targeted roGFP2, we show increased protein Cys oxidation and decreased reduction rates after oxidative challenge in {Delta}grxc5 plants in vivo, indicating kinetic uncoupling of the protein Cys redox state from glutathione redox potential. Protein Cys disulfide and S-glutathionylation formation rates after H2O2 treatment remained unchanged. Lack of class I GRX function in the stroma did not result in impaired carbon fixation. Our observations suggest specific roles for class I GRX in the efficient redox equilibration between EGSH and protein Cys in the plastid stroma as well as negligible cross-talk with metabolic regulation via the TRX system. We propose a model for stromal class I GRX function as efficient kinetic couplers of protein Cys redox state to the dynamic stromal EGSH and highlight the importance of identifying in vivo target proteins of GRXC5. One sentence summaryRemoval of class I GRX activity in the chloroplast stroma of P. patens kinetically uncouples GRX-dependent cysteine redox changes from the local glutathione redox potential, without an effect on NPQ or photosynthetic carbon reactions.

plant biology↗

bioRxiv2019

Identification of chloroplast envelope proteins with critical importance for cold acclimation

The ability of plants to cope with cold temperatures relies on their photosynthetic activity. This already demonstrates that the chloroplast is of utmost importance for cold acclimation and acquisition of freezing tolerance. During cold acclimation, the properties of the chloroplast change markedly. To provide the most comprehensive view of the protein repertoire of chloroplast envelope, we analysed this membrane system in Arabidopsis thaliana using MS-based proteomics. Profiling chloroplast envelope membranes was achieved by a cross comparison of protein intensities across plastid and the enriched membrane fraction both under normal and cold conditions. Multivariable logistic regression models the probabilities for the classification problem to address envelop localization. In total, we identified 38 envelope membrane intrinsic or associated proteins exhibiting altered abundance after cold acclimation. These proteins comprise several solute carries, such as the ATP/ADP antiporter NTT2 (substantially increased abundance) or the maltose exporter MEX1 (substantially decreased abundance). Remarkably, analysis of the frost recovery of ntt loss-of-function and mex1 overexpressor mutants confirmed that the comparative proteome is well suited to identify novel key factors involved in cold acclimation and acquisition of freezing tolerance. Moreover, for proteins with known physiological function we propose scenarios explaining their possible role in cold acclimation. Furthermore, spatial proteomics introduces a novel layer of complexity and enabled the identification of proteins differentially localized at the envelope membrane under the changing environmental regime.

plant biology↗

bioRxiv2019

Differential degradation of RNA species by autophagy related pathways in plants

An important function of the plant vacuole is the recycling of the delivered proteins and RNA by autophagy. We provide the first plant vacuolar small RNome by isolation of intact vacuoles from Barley and Arabidopsis, subsequent RNA purification and Next Generation Sequencing. In these vacuolar sRNomes, all types of cellular RNAs were found including those of chloroplast origin, suggesting a bulk-type of RNA transfer to, and breakdown in vacuoles. ATG5 is a major representative of autophagy genes and the vacuolar RNA composition in corresponding knockout plants differed clearly from controls as most chloroplast derived RNA species were missing. Moreover, the read length distribution of RNAs found in ATG5 mutants differed to control samples, indicating altered RNA processing. In contrast, vacuolar RNA length and composition of plants lacking the vacuolar RNase2 (rns2-2), involved in cellular RNA homeostasis, showed minor alterations, only. Our data therefore suggests that mainly autophagy components are responsible for selective transport and targeting of different RNA species into the vacuole for degradation. In addition, mature miRNAs were detected in all vacuolar preparations, however in ATG5 mutants at much lower frequency, indicating a new biological role for vacuolar miRNAs apart from becoming degraded.

plant biology↗