Biology subjects

Schulze, W.

Publications and source records attributed to Schulze, W..

7 recordsLinked to original sources

bioRxiv2025

SNRK3.15 is a crucial component of the sulfur deprivation response in Arabidopsis thaliana

Sulfate deprivation (-S) results in numerous metabolic and phenotypic alterations in plants. Kinases are often key players in transducing nutrient status signals to molecular components involved in metabolic and developmental program regulation, but despite the physiological importance of sulfur, to date, no signaling kinases have been identified in sulfur-deficiency signaling response programs. Here we show that the serine/threonine protein kinase CIPK14/SNRK3.15 plays a regulatory role in the -S response in Arabidopsis thaliana seedlings. Multiple molecular and physiological responses to -S are attenuated in snrk3.15 mutants, including both early adaptive responses and later emergency salvage processes including nutrient deficiency induced senescence. When grown in soil with sufficient sulfur supply, snrk3.15 mutants showed no clear phenotypes, including no difference in seed sulfur content. Lastly, the proteome dataset generated from Col-0 and snrk3.15.1 Arabidopsis seedlings under -S conditions for this project is the first of its kind and will be a valuable research resource. Proteomics data are available via ProteomeXchange with identifier PXD046612.

plant biology↗

bioRxiv2025

Making plant tissue accessible for cryo-electron tomography

Cryo-Electron Tomography (cryo-ET) allows to visualize the molecular architecture of pristinely preserved cells and tissues. The workflow of sample preparation for cryo-ET is rather complex; it involves vitrification by rapid freezing followed by cryo-Focused Ion Beam (FIB) milling rendering the volumes of interest thin enough for cryo-ET data acquisition. The established protocols for single cells grown on or deposited on EM-grids are not suitable for multicellular plant tissues. Plunge-freezing does not yield vitrified samples in most cases and must be replaced by high-pressure freezing. This, in turn, necessitates extensive modifications of the subsequent FIB milling procedures. In this communication we describe procedures for sample screening, targeted FIB milling guided by cryo-fluorescence microscopy and a novel lamella trimming step that allows to obtain homogenously thin lamellae suitable for cryo-ET. We have tested all the steps along the workflow with a variety of plant tissues including the moss Physcomitrium patens and tissues of Arabidopsis thaliana and Limonium bicolor. We could demonstrate that the workflow optimized for plant tissues allows to attain subnanometer resolution in cases where subtomogram averaging is applicable.

plant biology↗

bioRxiv2024

Learning and cognition in a decision made at reflex speed

It is widely accepted that more time and information yield better decisions. However, some decisions manage to combine speed and accuracy in an unusual way. Potentially their trick could be to use simplifying heuristics that works well for the most common condition but would lack flexibility otherwise. Here we describe an unexpected level of flexibility in a complex highspeed decision that is made faster than an Olympic sprinter can respond to the start gun. In this decision, archerfish observe the initial speed, direction, and height of falling prey and then use these initial values to turn right towards were ballistically falling prey would later land. To analyze the limits in flexibility of this highspeed decision we first developed and critically tested a system that allowed us to replace the usual ballistic relation between initial prey motion and the expected landing point with another deterministic rule. We discovered that, surprisingly, adult fish could reprogram their highspeed decision to the new rule. Moreover, after reprogramming their decision fish were immediately able to generalize their decision to novel untrained settings, showing a remarkable degree of abstraction in how the decision circuit represented the novel rule. The decision circuit is even capable of simultaneously using two distinct sets of rules, one for each of two visually distinct objects. The flexibility and level of cognition are unexpected for a decision that lacks a speed-accuracy tradeoff and is made in less than 100 ms. Our findings demonstrate the enormous potential highspeed decision making can have and strongly suggest that we presently underappreciate this form of decision making.

animal behavior and cognition↗

bioRxiv2022

A high confidence Physcomitrium patens plasmodesmata proteome by iterative scoring and validation reveals diversification of cell wall proteins during evolution

Cells of multicellular organisms exchange nutrients, building blocks and information. In animals, this happens via gap junctions, in plants via plasmodesmata (PD). PD have striking properties, translocating a large range of molecules from ions, to metabolites, RNA and proteins up to 40 kDa. PD are hard to characterize due to being deeply embedded into cell walls and the presence of several membranes. While previous studies of protein composition of PD from angiosperms identified large lists of proteins, few were validated. Here, we developed a PD scoring approach in conjunction with systematic localization on a large scale to define a high-confidence PD proteome of Physcomitrium patens. This high confidence PD proteome comprises nearly 300 proteins, which together with the bona fide PD proteins from literature, are made available in the public PDDB database. Conservation of localization across plant species strengthens the reliability of plant PD proteomes and provides a basis for exploring the evolution of this important organelle. In particular, the P. patens PD proteome was highly enriched in cell wall modifying proteins. Callose-degrading glycolyl hydrolase family 17 (GHL17) proteins are presented as an abundant PD protein family with representatives across an evolutionary scale. Exclusively members of the alpha-clade of the GHL17 family are shown to be PD localized and their orthologs occur only in plant species which have developed PD. Members of the EXORDIUM-family and xyloglucan transglycosylases are additional cell-wall located proteins highly abundant in the P. patens PD proteome also showing evolutionary diversification of PD localized family members from other clade members.

plant biology↗

bioRxiv2022

Structure of V-ATPase from citrus fruit

Vacuolar-type ATPases (V-ATPases) are rotary proton pumps involved in numerous essential cellular processes in all eukaryotes. Difficulty in obtaining preparations of purified V-ATPase from plants in sufficient quantities for structural analysis has hindered determining the 3D structure of the plant V-ATPase. We used the Legionella pneumophila effector SidK to affinity-purify the endogenous V-ATPase from lemon fruit. The preparation was sufficient to partially cover an electron microscopy specimen grid, allowing structure determination for the enzyme in two rotational states. The structure defines the ATP:H+ ratio of the enzyme, demonstrating that it can establish a maximum {Delta}pH of [~]3, which is insufficient to maintain the low pH observed in the vacuoles of juice sac cells in lemons and other citrus fruit. Compared to the yeast and mammalian enzymes, the membrane region of the plant V-ATPase lacks subunit f and possesses an unusual configuration of transmembrane helices. Subunit H, which inhibits ATP hydrolysis in the isolated catalytic region of V-ATPase, adopts two different conformations in the intact complex, hinting at a role in modulating activity in the intact enzyme.

biochemistry↗

bioRxiv2019

Plasma membrane associated Receptor Like Kinases relocalise to plasmodesmata in response to osmotic stress.

Plasmodesmata act as key elements in intercellular communication, coordinating processes related to plant growth, development and responses to environmental stresses. While many of the developmental, biotic and abiotic signals are primarily perceived at the plasma membrane (PM) by receptor proteins, plasmodesmata also cluster receptor-like activities and whether or not these two pathways interact is currently unknown.\n\nHere we show that specific PM-located Leucine-Rich-Repeat Receptor-Like-Kinases (LRR-RLKs), KIN7 and IMK2, which under optimal growth conditions are absented from plasmodesmata, rapidly relocate and cluster to the pores in response to osmotic stress. This process is remarkably fast, it is not a general feature of PM-associated proteins and is independent of sterol- and sphingolipid-membrane composition. Focusing on KIN7, previously reported to be involved in stress responses, we show that relocalisation upon mannitol depends on KIN7 phosphorylation. Loss-of-function mutation in KIN7 induces delay in lateral root (LR) development and the mutant is affected in the root response to mannitol stress. Callose-mediated plasmodesmata regulation is known to regulate LR development. We found that callose levels are reduced in kin7 mutant background with a root phenotype resembling ectopic expression of PdBG1, an enzyme that degrades callose at the pores. Both the LR and callose phenotypes can be complemented by expression of KIN7 -wild-type and -phosphomimic variants but not by KIN7 phosphodead mutant which fails to relocalise at plasmodesmata. Together the data indicate that re-organisation of RLKs to plasmodesmata is important for the regulation of callose and LR development as part of the plant response to osmotic stress.

plant biology↗

bioRxiv2019

NRT2.1 phosphorylation prevents root high affinity nitrate uptake activity in Arabidopsis thaliana

In Arabidopsis thaliana, NRT2.1 codes for a main component of the root nitrate high-affinity transport system. Previous studies revealed that post-translational regulation of NRT2.1 plays an important role in the control of root nitrate uptake and that one mechanism could correspond to NRT2.1 C-terminus processing. To further investigate this hypothesis, we produced transgenic plants with truncated forms of NRT2.1. It revealed an essential sequence for NRT2.1 activity, located between the residues 494-513. Using a phospho-proteomic approach, we found that this sequence contains one phosphorylation site, at serine 501, which can inactivate NRT2.1 function when mimicking the constitutive phosphorylation of this residue in transgenic plants. This phenotype could neither be explained by changes in abundance of NRT2.1 and NAR2.1, a partner protein of NRT2.1, nor by a lack of interaction between these two proteins. Finally, the relative level of serine 501 phosphorylation was found to be modulated by nitrate in wildtype plants. Altogether, these observations allowed us to propose a model for a new and essential mechanism for the regulation of NRT2.1 activity.

plant biology↗