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Publikationen - Molekulare Signalverarbeitung

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Bücher und Buchkapitel

Klemm, S.; Buhl, J.; Möller, B.; Bürstenbinder, K.; Quantitative analysis of microtubule organization in leaf epidermis pavement cells (Hussey, P.J., Wang, P.). The Plant Cytoskeleton 2604, 43-61, (2023) ISBN: 978-1-0716-2866-9 DOI: 10.1007/978-1-0716-2867-6_4

Leaf epidermis pavement cells form highly complex shapes with interlocking lobes and necks at their anticlinal walls. The microtubule cytoskeleton plays essential roles in pavement cell morphogenesis, in particular at necks. Vice versa, shape generates stress patterns that regulate microtubule organization. Genetic or pharmacological perturbations that affect pavement cell shape often affect microtubule organization. Pavement cell shape and microtubule organization are therefore closely interconnected. Here, we present commonly used approaches for the quantitative analysis of pavement cell shape characteristics and of microtubule organization. In combination with ablation experiments, these methods can be applied to investigate how different genotypes (or treatments) affect the organization and stress responsiveness of the microtubule cytoskeleton.
Publikation

Terrile, M. C.; Tebez, N. M.; Colman, S. L.; Mateos, J. L.; Morato-López, E.; Sánchez-López, N.; Izquierdo-Álvarez, A.; Marina, A.; Calderón Villalobos, L. I. A.; Estelle, M.; Martínez-Ruiz, A.; Fiol, D. F.; Casalongué, C. A.; Iglesias, M. J.; S-Nitrosation of E3 ubiquitin ligase complex components regulates hormonal signalings in Arabidopsis Front. Plant Sci. 12, 794582, (2022) DOI: 10.3389/fpls.2021.794582

E3 ubiquitin ligases mediate the last step of the ubiquitination pathway in the ubiquitin-proteasome system (UPS). By targeting transcriptional regulators for their turnover, E3s play a crucial role in every aspect of plant biology. In plants, SKP1/CULLIN1/F-BOX PROTEIN (SCF)-type E3 ubiquitin ligases are essential for the perception and signaling of several key hormones including auxins and jasmonates (JAs). F-box proteins, TRANSPORT INHIBITOR RESPONSE 1 (TIR1) and CORONATINE INSENSITIVE 1 (COI1), bind directly transcriptional repressors AUXIN/INDOLE-3-ACETIC ACID (AUX/IAA) and JASMONATE ZIM-DOMAIN (JAZ) in auxin- and JAs-depending manner, respectively, which permits the perception of the hormones and transcriptional activation of signaling pathways. Redox modification of proteins mainly by S-nitrosation of cysteines (Cys) residues via nitric oxide (NO) has emerged as a valued regulatory mechanism in physiological processes requiring its rapid and versatile integration. Previously, we demonstrated that TIR1 and Arabidopsis thaliana SKP1 (ASK1) are targets of S-nitrosation, and these NO-dependent posttranslational modifications enhance protein-protein interactions and positively regulate SCFTIR1 complex assembly and expression of auxin response genes. In this work, we confirmed S-nitrosation of Cys140 in TIR1, which was associated in planta to auxin-dependent developmental and stress-associated responses. In addition, we provide evidence on the modulation of the SCFCOI1 complex by different S-nitrosation events. We demonstrated that S-nitrosation of ASK1 Cys118 enhanced ASK1-COI1 protein-protein interaction. Overexpression of non-nitrosable ask1 mutant protein impaired the activation of JA-responsive genes mediated by SCFCOI1 illustrating the functional relevance of this redox-mediated regulation in planta. In silico analysis positions COI1 as a promising S-nitrosation target, and demonstrated that plants treated with methyl JA (MeJA) or S-nitrosocysteine (NO-Cys, S-nitrosation agent) develop shared responses at a genome-wide level. The regulation of SCF components involved in hormonal perception by S-nitrosation may represent a key strategy to determine the precise time and site-dependent activation of each hormonal signaling pathway and highlights NO as a pivotal molecular player in these scenarios.
Publikation

Zang, J.; Klemm, S.; Pain, C.; Duckney, P.; Bao, Z.; Stamm, G.; Kriechbaumer, V.; Bürstenbinder, K.; Hussey, P. J.; Wang, P.; A novel plant actin-microtubule bridging complex regulates cytoskeletal and ER structure at ER-PM contact sites Curr. Biol. 31, 1251-1260, (2021) DOI: 10.1016/j.cub.2020.12.009

In plants, the cortical endoplasmic reticulum (ER) network is connected to the plasma membrane (PM) through the ER-PM contact sites (EPCSs), whose structures are maintained by EPCS resident proteins and the cytoskeleton.1-7 Strong co-alignment between EPCSs and the cytoskeleton is observed in plants,1,8 but little is known of how the cytoskeleton is maintained and regulated at the EPCS. Here, we have used a yeast-two-hybrid screen and subsequent in vivo interaction studies in plants by fluorescence resonance energy transfer (FRET)-fluorescence lifetime imaging microscopy (FLIM) analysis to identify two microtubule binding proteins, KLCR1 (kinesin-light-chain-related protein 1) and IQD2 (IQ67-domain 2), that interact with the actin binding protein NET3C and form a component of plant EPCS that mediates the link between the actin and microtubule networks. The NET3C-KLCR1-IQD2 module, acting as an actin-microtubule bridging complex, has a direct influence on ER morphology and EPCS structure. Their loss-of-function mutants, net3a/NET3C RNAi, klcr1, or iqd2, exhibit defects in pavement cell morphology, which we suggest is linked to the disorganization of both actin filaments and microtubules. In conclusion, our results reveal a novel cytoskeletal-associated complex, which is essential for the maintenance and organization of cytoskeletal structure and ER morphology at the EPCS and for normal plant cell morphogenesis.
Preprints

Zang, J.; Klemm, S.; Pain, C.; Duckney, P.; Bao, Z.; Stamm, G.; Kriechbaumer, V.; Bürstenbinder, K.; Hussey, P. J.; Wang, P.; A Novel Plant Actin-Microtubule Bridging Complex Regulates Cytoskeletal and ER Structure at Endoplasmic Reticulum-Plasma Membrane Contact Sites (EPCS) SSRN Electronic Journal (2020) DOI: 10.2139/ssrn.3581370

In plants, the cortical ER network is connected to the plasma membrane through the ER-PM contact sites (EPCS), whose structures are maintained by EPCS resident proteins and the cytoskeleton. Strong co-alignment between EPCS and the cytoskeleton is observed in plants, but little is known of how the cytoskeleton is maintained and regulated at the EPCS. Here we have used a yeast-two-hybrid screen and subsequent in vivo interaction studies in plants by FRET-FLIM analysis, to identify two microtubule binding proteins, KLCR1 (Kinesin Light Chain Related protein 1) and IQD2 (IQ67-Domain 2) that interact with the actin binding protein NET3C and form a component of plant EPCS, that mediates the link between the actin and microtubule networks. The NET3C-KLCR1-IQD2 module, acting as an actin-microtubule bridging complex, has a direct influence on ER morphology. Their loss of function mutants, net3a/NET3C RNAi, 0klcr1 or iqd2, exhibit defects in pavement cell morphology which we suggest is linked to the disorganization of both actin filaments and microtubules. In conclusion, our results reveal a novel cytoskeletal associated complex, which is essential for the maintenance and organization of both cytoskeletal structure and ER morphology at the EPCS, and for normal plant cell morphogenesis.
Publikation

Mitra, D.; Klemm, S.; Kumari, P.; Quegwer, J.; Möller, B.; Poeschl, Y.; Pflug, P.; Stamm, G.; Abel, S.; Bürstenbinder, K.; Microtubule-associated protein IQ67 DOMAIN5 regulates morphogenesis of leaf pavement cells in Arabidopsis thaliana J. Exp. Bot. 70, 529-543, (2019) DOI: 10.1093/jxb/ery395

Plant microtubules form a highly dynamic intracellular network with important roles for regulating cell division, cell proliferation and cell morphology. Its organization and dynamics are coordinated by various microtubule-associated proteins (MAPs) that integrate environmental and developmental stimuli to fine-tune and adjust cytoskeletal arrays. IQ67 DOMAIN (IQD) proteins recently emerged as a class of plant-specific MAPs with largely unknown functions. Here, using a reverse genetics approach, we characterize Arabidopsis IQD5 in terms of its expression domains, subcellular localization and biological functions. We show that IQD5 is expressed mostly in vegetative tissues, where it localizes to cortical microtubule arrays. Our phenotypic analysis of iqd5 loss-of-function lines reveals functions of IQD5 in pavement cell (PC) shape morphogenesis. Histochemical analysis of cell wall composition further suggests reduced rates of cellulose deposition in anticlinal cell walls, which correlate with reduced anisotropic expansion. Lastly, we demonstrate IQD5-dependent recruitment of calmodulin calcium sensors to cortical microtubule arrays and provide first evidence for important roles of calcium in regulation of PC morphogenesis. Our work thus identifies IQD5 as a novel player in PC shape regulation, and, for the first time, links calcium signaling to developmental processes that regulate anisotropic growth in PCs.
Bücher und Buchkapitel

Möller, B.; Poeschl, Y.; Klemm, S.; Bürstenbinder, K.; Morphological Analysis of Leaf Epidermis Pavement Cells with PaCeQuant (Cvrčková, F. & Žárský, V., eds.). Methods Mol. Biol. 1992, 329-349, (2019) ISBN: 978-1-4939-9469-4 DOI: 10.1007/978-1-4939-9469-4_22

Morphological analysis of cell shapes requires segmentation of cell contours from input images and subsequent extraction of meaningful shape descriptors that provide the basis for qualitative and quantitative assessment of shape characteristics. Here, we describe the publicly available ImageJ plugin PaCeQuant and its associated R package PaCeQuantAna, which provides a pipeline for fully automatic segmentation, feature extraction, statistical analysis, and graphical visualization of cell shape properties. PaCeQuant is specifically well suited for analysis of jigsaw puzzle-like leaf epidermis pavement cells from 2D input images and supports the quantification of global, contour-based, skeleton-based, and pavement cell-specific shape descriptors.
Preprints

Mitra, D.; Kumari, P.; Quegwer, J.; Klemm, S.; Möller, B.; Poeschl, Y.; Pflug, P.; Stamm, G.; Abel, S.; Bürstenbinder, K.; Microtubule-associated protein IQ67 DOMAIN5 regulates interdigitation of leaf pavement cells in Arabidopsis thaliana bioRxiv (2018) DOI: 10.1101/268466

Plant microtubules form a highly dynamic intracellular network with important roles for regulating cell division, cell proliferation and cell morphology. Its organization and dynamics are coordinated by various microtubule-associated proteins (MAPs) that integrate environmental and developmental stimuli to fine-tune and adjust cytoskeletal arrays. IQ67 DOMAIN (IQD) proteins recently emerged as a class of plant-specific MAPs with largely unknown functions. Here, using a reverse genetics approach, we characterize Arabidopsis IQD5 in terms of its expression domains, subcellular localization and biological functions. We show that IQD5 is expressed mostly in vegetative tissues, where it localizes to cortical microtubule arrays. Our phenotypic analysis of iqd5 loss-of-function lines reveals functions of IQD5 in pavement cell (PC) shape morphogenesis, as indicated by reduced interdigitation of neighboring cells in the leaf epidermis of iqd5 mutants. Histochemical analysis of cell wall composition further suggests reduced rates of cellulose deposition in anticlinal cell walls, which correlate with reduced asymmetric expansion. Lastly, we provide evidence for IQD5-dependent recruitment of calmodulin calcium sensors to cortical microtubule arrays. Our work thus identifies IQD5 as a novel player in PC shape regulation, and, for the first time, links calcium signaling to developmental processes that regulate multi-polar growth in PCs.
Publikation

Bagchi, R.; Melnyk, C. W.; Christ, G.; Winkler, M.; Kirchsteiner, K.; Salehin, M.; Mergner, J.; Niemeyer, M.; Schwechheimer, C.; Calderón Villalobos, L. I. A.; Estelle, M.; The Arabidopsis ALF4 protein is a regulator of SCF E3 ligases EMBO J. 37, 255-268, (2018) DOI: 10.15252/embj.201797159

The cullin‐RING E3 ligases (CRLs) regulate diverse cellular processes in all eukaryotes. CRL activity is controlled by several proteins or protein complexes, including NEDD8, CAND1, and the CSN. Recently, a mammalian protein called Glomulin (GLMN) was shown to inhibit CRLs by binding to the RING BOX (RBX1) subunit and preventing binding to the ubiquitin‐conjugating enzyme. Here, we show that Arabidopsis ABERRANT LATERAL ROOT FORMATION4 (ALF4) is an ortholog of GLMN. The alf4 mutant exhibits a phenotype that suggests defects in plant hormone response. We show that ALF4 binds to RBX1 and inhibits the activity of SCFTIR1, an E3 ligase responsible for degradation of the Aux/IAA transcriptional repressors. In vivo, the alf4 mutation destabilizes the CUL1 subunit of the SCF. Reduced CUL1 levels are associated with increased levels of the Aux/IAA proteins as well as the DELLA repressors, substrate of SCFSLY1. We propose that the alf4 phenotype is partly due to increased levels of the Aux/IAA and DELLA proteins.
Publikation

Iglesias, M. J.; Terrile, M. C.; Correa-Aragunde, N.; Colman, S. L.; Izquierdo-Álvarez, A.; Fiol, D. F.; París, R.; Sánchez-López, N.; Marina, A.; Calderón Villalobos, L. I. A.; Estelle, M.; Lamattina, L.; Martínez-Ruiz, A.; Casalongué, C. A.; Regulation of SCFTIR1/AFBs E3 ligase assembly by S-nitrosylation of Arabidopsis SKP1-like1 impacts on auxin signaling Redox Biol. 18, 200-210, (2018) DOI: 10.1016/j.redox.2018.07.003

The F-box proteins (FBPs) TIR1/AFBs are the substrate recognition subunits of SKP1–cullin–F-box (SCF) ubiquitin ligase complexes and together with Aux/IAAs form the auxin co-receptor. Although tremendous knowledge on auxin perception and signaling has been gained in the last years, SCFTIR1/AFBs complex assembly and stabilization are emerging as new layers of regulation. Here, we investigated how nitric oxide (NO), through S-nitrosylation of ASK1 is involved in SCFTIR1/AFBs assembly. We demonstrate that ASK1 is S-nitrosylated and S-glutathionylated in cysteine (Cys) 37 and Cys118 residues in vitro. Both, in vitro and in vivo protein-protein interaction assays show that NO enhances ASK1 binding to CUL1 and TIR1/AFB2, required for SCFTIR1/AFB2 assembly. In addition, we demonstrate that Cys37 and Cys118 are essential residues for proper activation of auxin signaling pathway in planta. Phylogenetic analysis revealed that Cys37 residue is only conserved in SKP proteins in Angiosperms, suggesting that S-nitrosylation on Cys37 could represent an evolutionary adaption for SKP1 function in flowering plants. Collectively, these findings indicate that multiple events of redox modifications might be part of a fine-tuning regulation of SCFTIR1/AFBs for proper auxin signal transduction.
Publikation

García, M. L.; Bó, E. D.; da Graça, J. V.; Gago-Zachert, S.; Hammond, J.; Moreno, P.; Natsuaki, T.; Pallás, V.; Navarro, J. A.; Reyes, C. A.; Luna, G. R.; Sasaya, T.; Tzanetakis, I. E.; Vaira, A. M.; Verbeek, M.; ICTV Report Consortium, .; Corrigendum: ICTV Virus Taxonomy Profile: Ophioviridae J. Gen. Virol. 99, 949-949, (2018) DOI: 10.1099/jgv.0.001093

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