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Publikationen - Molekulare Signalverarbeitung

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White, M. D., Klecker, M., Hopkinson, R. J., Weits, D. A., Mueller, C., Naumann, C., O’Neill, R., Wickens, J., Yang, J., Brooks-Bartlett, J. C., Garman, E. F., Grossmann, T. N., Dissmeyer, N. & Flashman, E. Plant cysteine oxidases are dioxygenases that directly enable arginyl transferase-catalysed arginylation of N-end rule targets Nature Commun 8, 14690, (2017) DOI: 10.1038/ncomms14690

Crop yield loss due to flooding is a threat to food security. Submergence-induced hypoxia in plants results in stabilization of group VII ETHYLENE RESPONSE FACTORs (ERF-VIIs), which aid survival under these adverse conditions. ERF-VII stability is controlled by the N-end rule pathway, which proposes that ERF-VII N-terminal cysteine oxidation in normoxia enables arginylation followed by proteasomal degradation. The PLANT CYSTEINE OXIDASEs (PCOs) have been identified as catalysts of this oxidation. ERF-VII stabilization in hypoxia presumably arises from reduced PCO activity. We directly demonstrate that PCO dioxygenase activity produces Cys-sulfinic acid at the N terminus of an ERF-VII peptide, which then undergoes efficient arginylation by an arginyl transferase (ATE1). This provides molecular evidence of N-terminal Cys-sulfinic acid formation and arginylation by N-end rule pathway components, and a substrate of ATE1 in plants. The PCOs and ATE1 may be viable intervention targets to stabilize N-end rule substrates, including ERF-VIIs, to enhance submergence tolerance in agriculture.

Möller, B., Pöschl, Y., Plötner, R. & Bürstenbinder, K. PaCeQuant: A tool for high-throughput quantification of pavement cell shape characteristics. Plant Physiol. 175, 988-1017, (2017) DOI: 10.1104/pp.17.00961

Pavement cells (PCs) are the most frequently occurring cell type in the leaf epidermis and play important roles in leaf growth and function. In many plant species, PCs form highly complex jigsaw puzzle shaped cells with interlocking lobes. Understanding of their development is of high interest for plant science research because of their importance for leaf growth and hence for plant fitness and crop yield. Studies of PC development, however, are limited because robust methods are lacking that enable automatic segmentation and quantification of PC shape parameters suitable to reflect their cellular complexity. Here, we present our new ImageJ-based tool, PaCeQuant, which provides a fully automatic image analysis workflow for PC shape quantification. PaCeQuant automatically detects cell boundaries of PCs from confocal input images, and enables manual correction of automatic segmentation results or direct import of manually segmented cells. PaCeQuant simultaneously extracts 27 shape features that include global, contour-based, skeleton-based and PC-specific object descriptors. In addition, we included a method for classification and analysis of lobes at two-cell-junctions and three-cell-junctions, respectively. We provide an R script for graphical visualization and statistical analysis. We validated PaCeQuant by extensive comparative analysis to manual segmentation and existing quantification tools, and demonstrated its usability to analyze PC shape characteristics during development and between different genotypes. PaCeQuant thus provides a platform for robust, efficient and reproducible quantitative analysis of PC shape characteristics that can easily be applied to study PC development in large data sets.

Gantner, J., Ilse, T., Ordon, J., Kretschmer, C., Gruetzner, R., Loefke, C., Dagdas, Y., Buerstenbinder, K., Marillonnet, S. & Stuttmann, J. Peripheral infrastructure vectors and an extended set of plant parts for the modular cloning system bioRxiv (2017) DOI: 10.1101/237768

Standardized DNA assembly strategies facilitate the generation of multigene constructs from collections of building blocks in plant synthetic biology. A common syntax for hierarchical DNA assembly following the Golden Gate principle employing Type IIs restriction endonucleases was recently developed, and underlies the Modular Cloning and GoldenBraid systems. In these systems, transcriptional units and/or multigene constructs are assembled from libraries of standardized building blocks, also referred to as phytobricks, in several hierarchical levels and by iterative Golden Gate reactions. This combinatorial assembly strategy meets the increasingly complex demands in biotechnology and bioengineering, and also represents a cost-efficient and versatile alternative to previous molecular cloning techniques. For Modular Cloning, a collection of commonly used Plant Parts was previously released together with the Modular Cloning toolkit itself, which largely facilitated the adoption of this cloning system in the research community. Here, a collection of approximately 80 additional phytobricks is provided. These phytobricks comprise e.g. modules for inducible expression systems, different promoters or epitope tags, which will increase the versatility of Modular Cloning-based DNA assemblies. Furthermore, first instances of a "peripheral infrastructure" around Modular Cloning are presented: While available toolkits are designed for the assembly of plant transformation constructs, vectors were created to also use coding sequence-containing phytobricks directly in yeast two hybrid interaction or bacterial infection assays. Additionally, DNA modules and assembly strategies for connecting Modular Cloning with Gateway Cloning are presented, which may serve as an interface between available resources and newly adopted hierarchical assembly strategies. The presented material will be provided as a toolkit to the plant research community and will further enhance the usefulness and versatility of Modular Cloning.
Bücher und Buchkapitel

Flores, R., Gago-Zachert, S., De la Peña, M. & Navarro, B. Chrysanthemum Chlorotic Mottle Viroid. In: Viroids and Satellite. - Academic Press (Ed. A. Hadidi, et al.). 331-338, (2017) ISBN: eBook ISBN: 9780128017029; Hardcover ISBN: 9780128014981. DOI: 10.1016/B978-0-12-801498-1.00031-0

Publikationen in Druck

Wasternack, C. & Strnad, M. Jasmonates are signals in the biosynthesis of secondary metabolites — Pathways, transcription factors and applied aspects — A brief review. New Biotechnol. (2017) DOI: 10.1016/j.nbt.2017.09.007

Jasmonates (JAs) are signals in plant stress responses and development. One of the first observed and prominent responses to JAs is the induction of biosynthesis of different groups of secondary compounds. Among them are nicotine, isoquinolines, glucosinolates, anthocyanins, benzophenanthridine alkaloids, artemisinin, and terpenoid indole alkaloids (TIAs), such as vinblastine. This brief review describes modes of action of JAs in the biosynthesis of anthocyanins, nicotine, TIAs, glucosinolates and artemisinin. After introducing JA biosynthesis, the central role of the SCFCOI1-JAZ co-receptor complex in JA perception and MYB-type and MYC-type transcription factors is described. Brief comments are provided on primary metabolites as precursors of secondary compounds. Pathways for the biosynthesis of anthocyanin, nicotine, TIAs, glucosinolates and artemisinin are described with an emphasis on JA-dependent transcription factors, which activate or repress the expression of essential genes encoding enzymes in the biosynthesis of these secondary compounds. Applied aspects are discussed using the biotechnological formation of artemisinin as an example of JA-induced biosynthesis of secondary compounds in plant cell factories.

Dong, H., Dumenil, J., Lu, F.-H., Na, L., Vanhaeren, H., Naumann, C., Klecker, M., Prior, R., Smith, C., McKenzie, N., Saalbach, G., Chen, L., Xia, T., Gonzalez, N., Seguela, M., Inze, D., Dissmeyer, N., Li, Y. & Bevan, M. W. Ubiquitylation activates a peptidase that promotes cleavage and destabilization of its activating E3 ligases and diverse growth regulatory proteins to limit cell proliferation in Arabidopsis Gen. Dev 31, 197-208, (2017) DOI: 10.1101/gad.292235.116

The characteristic shapes and sizes of organs are established by cell proliferation patterns and final cell sizes, but the underlying molecular mechanisms coordinating these are poorly understood. Here we characterize a ubiquitin-activated peptidase called DA1 that limits the duration of cell proliferation during organ growth in Arabidopsis thaliana. The peptidase is activated by two RING E3 ligases, Big Brother (BB) and DA2, which are subsequently cleaved by the activated peptidase and destabilized. In the case of BB, cleavage leads to destabilization by the RING E3 ligase PROTEOLYSIS 1 (PRT1) of the N-end rule pathway. DA1 peptidase activity also cleaves the deubiquitylase UBP15, which promotes cell proliferation, and the transcription factors TEOSINTE BRANCED 1/CYCLOIDEA/PCF 15 (TCP15) and TCP22, which promote cell proliferation and repress endoreduplication. We propose that DA1 peptidase activity regulates the duration of cell proliferation and the transition to endoreduplication and differentiation during organ formation in plants by coordinating the destabilization of regulatory proteins. 

Bürstenbinder, K., Möller, B., Plötner, R., Stamm, G., Hause, G., Mitra, D. & Abel, S. The IQD family of calmodulin-binding proteins links calcium signaling to microtubules, membrane subdomains, and the nucleus. Plant Physiol 173, 1692-1708, (2017) DOI: 10.1104/pp.16.01743

Calcium (Ca2+) signaling and dynamic reorganization of the cytoskeleton are essential processes for the coordination and control of plant cell shape and cell growth. Calmodulin (CaM) and closely related CaM-like polypeptides (CML) are principal sensors of Ca2+ signals. CaM/CMLs decode and relay information encrypted by the second messenger via differential interactions with a wide spectrum of targets to modulate their diverse biochemical activities. The plant-specific IQ67-DOMAIN (IQD) family emerged as the possibly largest class of CaM interacting proteins with undefined molecular functions and biological roles. Here, we show that the 33 members of the IQD family in Arabidopsis thaliana differentially localize, using GFP-tagged proteins, to multiple and distinct subcellular sites, including microtubule (MT) arrays, plasma membrane microdomains, and nuclear compartments. Intriguingly, the various IQD-specific localization patterns coincide with the subcellular patterns of IQD-dependent recruitment of CaM, suggesting that the diverse IQD members sequester Ca2+-CaM signaling modules to specific subcellular sites for precise regulation of Ca2+-dependent processes. Because MT localization is a hallmark of most IQD family members, we quantitatively analyzed GFP-labeled MT arrays in tobacco cells transiently expressing GFP-IQD fusions and observed IQD-specific MT patterns, which point to a role of IQDs in MT organization and dynamics. Indeed, stable overexpression of select IQD proteins in Arabidopsis altered cellular MT orientation, cell shape, and organ morphology. Because IQDs share biochemical properties with scaffold proteins, we propose that IQD families provide an assortment of platform proteins for integrating CaM-dependent Ca2+ signaling at multiple cellular sites to regulate cell function, shape, and growth. 


Wasternack, C A plant's balance of growth and defense – revisited. New Phytol 215, 1291-1294, (2017) DOI: 10.1111/nph.14720

The sessile lifestyle of plants requires a permanent and efficient adjustment to environmental stresses caused by biotic factors, such as pathogens and herbivores, or abiotic factors, such as drought and salt. Any defense responses, however, are costly, and investment into defense leads to reduced growth. These plant growth–defense tradeoffs, with simultaneous activation of defense and maintenance of growth, are critical for crop breeding. For some stresses, such as wounding by herbivores, the cost–benefit ratio in the growth–defense tradeoff has been tested in native populations; a costly jasmonic acid (JA)-induced defense response has been shown, which is down-regulated when the defense is not required (Baldwin, 1998). JA is the central player in many stress responses: inhibition of root growth, photosynthesis, and leaf growth (Zhang & Turner, 2008), induction of defense proteins, formation of secondary compounds active in defense and defense upon bacterial infection are JA-induced processes with consequences for growth (Wasternack & Hause, 2013; reviewed in Havko et al., 2016).
This article is a Commentary on Major et al., 215: 1533–1547.

Bürstenbinder, K., Mitra, D. & Quegwer, J.  Functions of IQD proteins as hubs in cellular calcium and auxin signaling: a toolbox for shape formation and tissue-specification in plants? Plant Signal Behav 12 , e1331198, (2017) DOI: 10.1080/15592324.2017.1331198

Ca2+ ions play pivotal roles as second messengers in intracellular signal transduction, and coordinate many biological processes. Changes in intracellular Ca2+ levels are perceived by Ca2+ sensors such as CaM/CML proteins, which transduce Ca2+ signals into cellular responses by regulation of diverse target proteins. Insights into molecular functions of CaM targets are thus essential to understand the molecular and cellular basis of Ca2+ signaling. During the last decade, IQD proteins emerged as the largest class of CaM targets in plants with mostly unknown functions. In the March issue of Plant Physiology, we presented the first comprehensive characterization of the 33-membered IQD family in Arabidopsis thaliana. We showed, by analysis of the subcellular localization of translational GFP fusion proteins, that most IQD members label MTs, and additionally often localize to the cell nucleus or to membranes, where the recruit CaM Ca2+ sensors. Important functions at MTs are supported by altered MT organization and plant growth in IQD gain-of-function lines. Because IQD proteins share structural hallmarks of scaffold proteins, we propose roles of IQDs in the assembly of macromolecular complexes to orchestrate Ca2+ CaM signaling from membranes to the nucleus. 

Abel, S. Phosphate scouting by root tips. Curr Opin Plant Biol. 39, 168-177, (2017) DOI: 10.1016/j.pbi.2017.04.016

Chemistry assigns phosphate (Pi) dominant roles in metabolism; however, it also renders the macronutrient a genuinely limiting factor of plant productivity. Pi bioavailability is restricted by low Pi mobility in soil and antagonized by metallic toxicities, which force roots to actively seek and selectively acquire the vital element. During the past few years, a first conceptual outline has emerged of the sensory mechanisms at root tips, which monitor external Pi and transmit the edaphic cue to inform root development. This review highlights new aspects of the Pi acquisition strategy of Arabidopsis roots, as well as a framework of local Pi sensing in the context of antagonistic interactions between Pi and its major associated metallic cations, Fe3+ and Al3+.
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