Search

SUMMARY: The final step in secretion is membrane fusion facilitated by SNARE proteins that reside in opposite membranes. The formation of a trans‐SNARE complex between one R and three Q coiled‐coiled SNARE domains drives the final approach of the membranes providing the mechanical energy for fusion. Biological control of this mechanism is exerted by additional domains within some SNAREs. For example, the N‐terminal Longin domain (LD) of R‐SNAREs (also called Vesicle‐associated membrane proteins, VAMPs) can fold back onto the SNARE domain blocking interaction with other cognate SNAREs. The LD may also determine the subcellular localization via interaction with other trafficking‐related proteins. Here, we provide cell‐biological and genetic evidence that phosphorylation of the Tyrosine57 residue regulates the functionality of VAMP721. We found that an aspartate mutation mimics phosphorylation, leading to protein instability and subsequent degradation in lytic vacuoles. The mutant SNARE also fails to rescue the defects of vamp721vamp722 loss‐of‐function lines in spite of its wildtype‐like localization within the secretory pathway and the ability to interact with cognate SNARE partners. Most importantly, it imposes a dominant negative phenotype interfering with root growth, normal secretion and cytokinesis in wildtype plants generating large aggregates that mainly contain secretory vesicles. Non‐phosphorylatable VAMP721Y57F needs higher gene dosage to rescue double mutants in comparison to native VAMP721 underpinning that phosphorylation modulates SNARE function. We propose a model where short‐lived phosphorylation of Y57 serves as a regulatory step to control VAMP721 activity, favoring its open state and interaction with cognate partners to ultimately drive membrane fusion. Significance Statement: The R‐SNARE proteins VAMP721/722 serve as crucial and highly redundant facilitators of membrane fusion within the secretory pathway. Our research has uncovered a short‐lived tyrosine phosphorylation site that exerts fine‐tuning of VAMP721's function in vesicle‐trafficking, illuminating the thin line between control and dysfunction of vesicle fusion. [ABSTRACT FROM AUTHOR]

Maize smut caused by the fungus Ustilago maydis is a widespread disease characterized by the development of large plant tumours. U. maydisis a biotrophic pathogen that requires living plant tissue for its development and establishes an intimate interaction zone between fungal hyphae and the plant plasma membrane. U. maydis actively suppresses plant defence responses by secreted protein effectors (1,2). Its effector repertoire comprises at least 386 genes mostly encoding proteins of unknown function (1,3,4) and expressed exclusively during the biotrophic stage (3).The U. maydis secretome also contains about 150 proteins with probable roles in fungal nutrition, fungal cell wall modification and host penetration as well as proteins unlikely to act in the fungal-host interface (4) like a chorismate mutase. Chorismate mutases are key enzymes of the shikimate pathway and catalyse the conversion of chorismate to prephenate, the precursor for tyrosine and phenylalanine synthesis. Root-knot nematodes inject a secreted chorismate mutase into plant cells likely to affect development (5,6). Here we show that the chorismate mutase Cmu1 secreted by U. maydis is a virulence factor. The enzyme is taken up by plant cells, can spread to neighbouring cells and changes the metabolic status of these cells through metabolic priming. Secreted chorismate mutases are found in many plant-associated microbes and might serve as general tools for host manipulation., The U. maydis genome (http://mips.helmholtz-muenchen.de/genre/proj/ustilago) contains genes for both a cytosolic chorismate mutase, designated aro7 (um04220), and a putatively secreted chorismate mutase, cmul (um05731). Cmu1 belongs to the AroQ class [...]

Polarized epithelia are fundamental to multicellular life. In animal epithelia, conserved junctional complexes establish membrane diffusion barriers, cellular adherence and sealing of the extracellular space (1). Plant cellular barriers are of independent evolutionary origin. The root endodermis strongly resembles a polarized epithelium and functions in nutrient uptake and stress resistance (2). Its defining features are the Casparian strips, belts of specialized cell wall material that generate an extracellular diffusion barrier (2). The mechanisms localizing Casparian strips are unknown. Here we identify and characterize a family of transmembrane proteins of previously unknown function. These 'CASPs' (Casparian strip membrane domain proteins) specifically mark a membrane domain that predicts the formation of Casparian strips. CASP1 displays numerous features required for a constituent of a plant junctional complex: it forms complexes with other CASPs; it becomes immobile upon localization; and it sediments like a large polymer. CASP double mutants display disorganized Casparian strips, demonstrating a role for CASPs in structuring and localizing this cell wall modification. To our knowledge, CASPs are the first molecular factors that are shown to establish a plasma membrane and extracellular diffusion barrier in plants, and represent a novel way of epithelial barrier formation in eukaryotes., In 1865 Robert Caspary described a novel cell type surrounding the vascular cylinder of roots (3). Caspary named this layer 'Schutzscheide', protective sheath, but during the twentieth century it was [...]

The plant signalling molecule auxin provides positional information in a variety of developmental processes by means of its differential distribution (gradients) within plant tissues (1). Thus, cellular auxin levels often [...]

Author(s): Sandra Richter [1]; Niko Geldner [1, 5]; Jarmo Schrader [1]; Hanno Wolters [1]; York-Dieter Stierhof [2]; Gabino Rios [3, 5]; Csaba Koncz [3]; David G. Robinson [4]; Gerd Jürgens [...]

Author(s): Tomasz Paciorek [1]; Eva ZažÃ­malová [2]; Nadia Ruthardt [3]; Jan Petrášek [2]; York-Dieter Stierhof [1]; Jürgen Kleine-Vehn [1]; David A. Morris [2, 4]; Neil Emans [3]; Gerd Jürgens [1]; [...]

Plants are indispensable on earth and their improvement in terms of food security is a need of time. The current study has been designed to investigate how biogenic zinc nanoparticles (Zn NPs) can improve the growth and development of Brassica napus L. In this study, Zn NPs were synthesized utilizing Mentha arvensis aqueous extracts, and their morphological and optical properties were assessed using UV-Visible spectrophotometry, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The synthesized Zn NPs were irregular in shape, indicating aggregation in pattern, with an average particle size of 30 nm, while XRD analysis revealed the crystalline structure of nanoparticles. The growth and development of B. napus varieties (Faisal canola and Shiralee) were assessed after foliar treatments with different concentrations of biogenic Zn NPs. In B. napus varieties, exposure to 15 mg/L Zn NPs dramatically increased chlorophyll, carotenoid content, and biomass accumulation. Similarly, proteomic analyses, on the other hand, revealed that proteins associated with photosynthesis, transport, glycolysis, and stress response in both Brassica varieties were substantially altered. Such exposure to Zn NPs, differential expression of genes associated with photosynthesis, ribosome structural constituents, and oxidative stress response were considerably upregulated in B. napus var. (Faisal and Shiralee canola). The results of this study revealed that foliar applications of biogenic Zn NPs influence the transcriptome and protein profiling positively, therefore stimulating plant growth and development. [ABSTRACT FROM AUTHOR]

Author(s): Niko Geldner [1, 2]; Jiří Friml [2, 3, 4, 5]; York-Dieter Stierhof [1]; Gerd Jürgens (corresponding author) [1]; Klaus Palme [3] Polar transport of the phytohormone auxin mediates various [...]