Biology subjects

Scholl, S.

Publications and source records attributed to Scholl, S..

5 recordsLinked to original sources

bioRxiv2021

Integration of computational modeling and quantitative cell physiology reveals central parameters for the brassinosteroid-regulated elongation growth along the axis of the Arabidopsis root

Brassinosteroids (BR) are key hormonal regulators of plant development. However, whereas the individual components of BR perception and signaling are well characterized experimentally, the question of how they can act and whether they are sufficient to carry out the critical function of cellular elongation remains open. Here, we combined computational modeling with quantitative cell physiology to understand the dynamics of the plasma membrane (PM)-localized BR response pathway during the initiation of cellular responses in the epidermis of the Arabidopsis root tip that are be linked to cell elongation. The model, consisting of ordinary differential equations, comprises the BR induced hyperpolarization of the PM, the acidification of the apoplast and subsequent cell wall swelling. We demonstrate that the competence of the root epidermal cells for the BR response predominantly depends on the amount and activity of H+-ATPases in the PM. The model further predicts that an influx of cations is required to compensate for the shift of positive charges caused by the apoplastic acidification. A potassium channel was subsequently identified and experimentally characterized, fulfilling this function. Thus, we established the landscape of components and parameters for physiological processes potentially linked to cell elongation, a central process in plant development.

plant biology↗

bioRxiv2021

CLCd and CLCf act redundantly at the TGN/EE and prevent acidification of the Golgi stack

The trans-Golgi network/early endosome (TGN/EE) serves as the central hub in which exo- and endocytic trafficking pathways converge and specificity of cargo routing needs to be achieved. Acidification is a hallmark of the TGN/EE and is maintained by the vacuolar H+-ATPase (V-ATPase) with support of proton-coupled antiporters. We show here that CLCd and CLCf, two distantly related members of the Arabidopsis chloride channel (CLC)-family that colocalize in the TGN/EE act redundantly and are essential for male gametophyte development. Combining an inducible knock-down approach and in vivo pH-measurements, we show here that reduced CLC-activity does not affect pH in the TGN/EE but causes accumulation of the V-ATPase in trans-Golgi cisternae leading to their hyper-acidification. Taken together, our results show that CLC-mediated anion transport into the TGN/EE is essential and affects spatio-temporal aspects of TGN/EE-maturation as well as its functional separation from the Golgi stack.

plant biology↗

bioRxiv2019

Pathogen-induced pH changes regulate the growth-defense balance of plants

Environmental adaptation of organisms relies on fast perception and response to external signals, which lead to developmental changes. Plant cell growth is strongly dependent on cell wall remodeling. However, little is known about cell wall-related sensing of biotic stimuli and the downstream mechanisms that coordinate growth and defense responses. We generated genetically encoded pH sensors to determine absolute pH changes across the plasma membrane in response to biotic stress. A rapid apoplastic acidification by phosphorylation-based proton pump activation was followed by an acidification of the cortical side of the plasma membrane in response to the fungus Fusarium oxysporum. The proton chemical gradient modulation immediately reduced cellulose synthesis and cell growth and, furthermore, had a direct influence on the pathogenicity of the fungus. All these effects were dependent on the COMPANION OF CELLULOSE SYNTHASE proteins that are thus at the nexus of plant growth and defense. Hence, our discoveries show a remarkable connection between plant biomass production, immunity, and pH control, and advance our ability to investigate the plant growth-defense balance.

plant biology↗

bioRxiv2018

Subtilase-mediated activation of CLEL peptides involves several processing events in consecutive compartments of the secretory pathway

Post-translationally modified peptides are involved in many aspects of plant growth and development. The maturation of these peptides from their larger precursors is still poorly understood. We show here that the biogenesis of CLEL6 and CLEL9 peptides in Arabidopsis thaliana requires a series of processing events in consecutive compartments of the secretory pathway. Following cleavage of the signal peptide upon entry into the endoplasmic reticulum (ER), the peptide precursors are processed in the cis-Golgi by the subtilase SBT6.1. SBT6.1-mediated cleavage within the variable domain allows for continued passage of the partially processed precursors through the secretory pathway, and is a prerequisite for subsequent post-translational modifications including tyrosine sulfation and proline hydroxylation within, and proteolytic maturation after exit from the Golgi. Activation by subtilase SBT3.8 in post-Golgi compartments depends on the N-terminal aspartate of the mature peptides. Our work highlights the complexity of post-translational precursor maturation allowing for stringent control of peptide biogenesis.

plant biology↗

bioRxiv2018

NHX-type Na+(K+)/H+ antiporter activity is required for endomembrane trafficking and ion homeostasis in Arabidopsis thaliana

The regulation of ion and pH homeostasis of endomembrane organelles is critical for functional protein trafficking, sorting and modification in eukaryotic cells. pH homeostasis is maintained through the activity of vacuolar H+-ATPases (V-ATPases) pumping protons (H+) into the endomembrane lumen, and counter-action by cation/proton exchangers such as the NHX family of Na+(K+)/H+ exchangers. In plants, disturbing V-ATPase activity at the trans-Golgi network/early endosome (TGN/EE) impairs secretory and endocytic trafficking. However, it is unclear if the endosomal NHX-type antiporters NHX5 and NHX6 play functionally similar roles in endomembrane trafficking through maintaining ion and pH homeostasis. Here we show through genetic, pharmacological, and live-cell imaging approaches that double knockout of endosomal isoforms NHX5 and NHX6 results in impairment of endosome motility, protein recycling at the TGN/EE, but not in the secretion of integral membrane proteins. Furthermore, we report that nhx5 nhx6 mutants are partially insensitive to osmotic swelling of TGN/EE induced by the monovalent cation ionophore monensin. Similarly, nhx5 nhx6 cells are unresponsive to late endosomal swelling by the phosphatidylinositol 3/4-kinase inhibitor wortmannin, demonstrating that NHX5 and NHX6 are required for maintaining endosomal cation balance. Lastly, we report that the distal region of the cytosolic tail of NHX6 is required for mediating NHX6 localisation to late endosomes, but does not appear to be essential for NHX6 function.

plant biology↗