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Maekawa T.,Max Planck Institute For Pflanzenzuchtungsforschung | Cheng W.,Beijing Normal University | Cheng W.,China National Institute of Biological Sciences | Spiridon L.N.,Institute of Biochemistry of the Romanian Academy | And 12 more authors.
Cell Host and Microbe | Year: 2011

Plants and animals have evolved structurally related innate immune sensors, designated NLRs, to detect intracellular nonself molecules. NLRs are modular, consisting of N-terminal coiled-coil (CC) or TOLL/interleukin-1 receptor (TIR) domains, a central nucleotide-binding (NB) domain, and C-terminal leucine-rich repeats (LRRs). The polymorphic barley mildew A (MLA) locus encodes CC-containing allelic immune receptors recognizing effectors of the pathogenic powdery mildew fungus. We report the crystal structure of an MLA receptor's invariant CC domain, which reveals a rod-shaped homodimer. MLA receptors also self-associate in vivo, but self-association appears to be independent of effector-triggered receptor activation. MLA CC mutants that fail to self-interact impair in planta cell death activity triggered by the CC domain alone and by an autoactive full-length MLA receptor that mimics its ATP-bound state. Thus, CC domain-dependent dimerization of the immune sensor defines a minimal functional unit and implies a role for the dimeric CC module in downstream immune signaling. © 2011 Elsevier Inc.


Takeda N.,Japan National Institute of Agrobiological Science | Takeda N.,Japan National Institute for Basic Biology | Takeda N.,Graduate University for Advanced Studies | Maekawa T.,Ludwig Maximilians University of Munich | And 3 more authors.
Plant Cell | Year: 2012

The common symbiosis pathway is at the core of symbiosis signaling between plants and soil microbes. In this pathway, calcium- and calmodulin-dependent protein kinase (CCaMK) plays a crucial role in integrating the signals both in arbuscular mycorrhizal symbiosis (AMS) and in root nodule symbiosis (RNS). However, the molecular mechanism by which CCaMK coordinates AMS and RNS is largely unknown. Here, we report that the gain-of-function (GOF) variants of CCaMK without the regulatory domains activate both AMS and RNS signaling pathways in the absence of symbiotic partners. This activation requires nuclear localization of CCaMK. Enforced nuclear localization of the GOF-CCaMK variants by fusion with a canonical nuclear localization signal enhances signaling activity of AMS and RNS. The GOF-CCaMK variant triggers formation of a structure similar to the prepenetration apparatus, which guides infection of arbuscular mycorrhizal fungi to host root cells. In addition, the GOF-CCaMK variants without the regulatory domains partly restore AMS but fail to support rhizobial infection in ccamk mutants. These data indicate that AMS, the more ancient type of symbiosis, can be mainly regulated by the kinase activity of CCaMK, whereas RNS, which evolved more recently, requires complex regulation performed by the regulatory domains of CCaMK. © 2012 American Society of Plant Biologists.


Nowack M.K.,Vlaams Institute for Biotechnology | Nowack M.K.,Ghent University | Harashima H.,University of Strasbourg | Dissmeyer N.,University of Strasbourg | And 9 more authors.
Developmental Cell | Year: 2012

Cyclin-dependent kinases (CDKs) are at the heart of eukaryotic cell-cycle control. The yeast Cdc2/CDC28 PSTAIRE kinase and its orthologs such as the mammalian Cdk1 have been found to be indispensable for cell-cycle progression in all eukaryotes investigated so far. CDKA;1 is the only PSTAIRE kinase in the flowering plant Arabidopsis and can rescue Cdc2/CDC28 mutants. Here, we show that cdka;1 null mutants are viable but display specific cell-cycle and developmental defects, e.g., in S phase entry and stem cell maintenance. We unravel that the crucial function of CDKA;1 is the control of the plant Retinoblastoma homolog RBR1 and that codepletion of RBR1 and CDKA;1 rescued most defects of cdka;1 mutants. Our work further revealed a basic cell-cycle control system relying on two plant-specific B1-type CDKs, and the triple cdk mutants displayed an early germline arrest. Taken together, our data indicate divergent functional differentiation of Cdc2-type kinases during eukaryote evolution. Nowack et al. find that mutants in CDKA;1, the only canonical PSTAIRE cyclin-dependent kinase (CDK) in Arabidopsis, are viable. CDKA;1's primary role during S phase entry is to regulate RBR1, an Rb homolog; however, plant-specific B1-type CDKs and CDKA;1 are partially redundant, sharing multiple roles throughout the cell cycle. © 2012 Elsevier Inc.


Bramsiepe J.,University of Strasbourg | Wester K.,University of Cologne | Weinl C.,Innsbruck Medical University | Roodbarkelari F.,Innsbruck Medical University | And 7 more authors.
PLoS Genetics | Year: 2010

Cell-fate specification is typically thought to precede and determine cell-cycle regulation during differentiation. Here we show that endoreplication, also known as endoreduplication, a specialized cell-cycle variant often associated with cell differentiation but also frequently occurring in malignant cells, plays a role in maintaining cell fate. For our study we have used Arabidopsis trichomes as a model system and have manipulated endoreplication levels via mutants of cell-cycle regulators and overexpression of cell-cycle inhibitors under a trichome-specific promoter. Strikingly, a reduction of endoreplication resulted in reduced trichome numbers and caused trichomes to lose their identity. Live observations of young Arabidopsis leaves revealed that dedifferentiating trichomes re-entered mitosis and were re-integrated into the epidermal pavement-cell layer, acquiring the typical characteristics of the surrounding epidermal cells. Conversely, when we promoted endoreplication in glabrous patterning mutants, trichome fate could be restored, demonstrating that endoreplication is an important determinant of cell identity. Our data lead to a new model of cell-fate control and tissue integrity during development by revealing a cell-fate quality control system at the tissue level. © 2010 Bramsiepe et al.


Bessire M.,University of Lausanne | Borel S.,University of Lausanne | Fabre G.,University of Lausanne | Carrac L.,University of Lausanne | And 9 more authors.
Plant Cell | Year: 2011

Although the multilayered structure of the plant cuticle was discovered many years ago, the molecular basis of its formation and the functional relevance of the layers are not understood. Here, we present the permeable cuticle1 (pec1) mutant of Arabidopsis thaliana, which displays features associated with a highly permeable cuticle in several organs. In pec1 flowers, typical cut in monomers, such as v-hydroxylated fatty acids and 10, 16-dihydroxypalmitate, are reduced to 40% of wild-type levels and are accompanied by the appearance of lipidic inclusions within the epidermal cell. The cuticular layer of the cell wall, rather than the cuticle proper, is structurally altered in pec1 petals. Therefore, a significant role for the formation of the diffusion barrier in petals can be attributed to this layer. Thus, pec1 defines a new class of mutants. The phenotypes of the pec1 mutant are caused by the knockout of ATP BINDING CASSETTEG32 (ABCG32), an ABC transporter from the PLEIOTROPIC DRUG RESISTANCE family that is localized at the plasma membrane of epidermal cells in a polar manner toward the surface of the organs. Our results suggest that ABCG32 is involved in the formation of the cuticular layer of the cell wall, most likely by exporting particular cut in precursors from the epidermal cell. © 2011 American Society of Plant Biologists. All rights reserved.


Schneeberger K.,Max Planck Institute For Pflanzenzuchtungsforschung
BioSpektrum | Year: 2011

The advent of Next Generation Sequencing has tremendous influence on plant genetics. Genetic mapping of mutant loci can be performed within days, instead of months as it would take using conventional methods.


Kaschani F.,University of Duisburg - Essen | Clerc J.,University of Gottingen | Krahn D.,University of Duisburg - Essen | Bier D.,Chemical Genomics Center der Max Planck Gesellschaft | And 6 more authors.
Angewandte Chemie - International Edition | Year: 2012

Exceptionally specific: The natural-product-like structural complexity of a bicyclic hydantoin was exploited to generate the novel, highly specific activity-based profiling probe (ABPP) Mrl-Rh (Rh=rhodamine; see picture) for glyceraldehyde 3-phosphate dehydrogenases. This probe can be used to investigate activity changes of this enzyme class during plant-pathogen interactions. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.


Salomon S.,Max Planck Institute For Pflanzenzuchtungsforschung | Grunewald D.,Max Planck Institute For Pflanzenzuchtungsforschung | Stuber K.,Max Planck Institute For Pflanzenzuchtungsforschung | Schaaf S.,Max Planck Institute For Pflanzenzuchtungsforschung | And 4 more authors.
Plant Physiology | Year: 2010

Membrane compartmentalization and trafficking within and between cells is considered an essential cellular property of higher eukaryotes. We established a high-throughput imaging method suitable for the quantitative detection of membrane compartments at subcellular resolution in intact epidermal tissue. Whole Arabidopsis (Arabidopsis thaliana) cotyledon leaves were subjected to quantitative confocal laser microscopy using automated image acquisition, computational pattern recognition, and quantification of membrane compartments. This revealed that our method is sensitive and reliable to detect distinct endomembrane compartments. We applied quantitative confocal laser microscopy to a transgenic line expressing GFP-2xFYVE as a marker for endosomal compartments during biotic or abiotic stresses, and detected markedly quantitative adaptations in response to changing environments. Using a transgenic line expressing the plasma membrane-resident syntaxin GFP-PEN1, we quantified the pathogen-inducible extracellular accumulation of this fusion protein at fungal entry sites. Our protocol provides a platform to study the quantitative and dynamic changes of endomembrane trafficking, and potential adaptations of this machinery to physiological stress. © 2010 American Society of Plant Biologists.


Bednarek P.,Max Planck Institute For Pflanzenzuchtungsforschung | Kwon C.,Dankook University | Schulze-Lefert P.,Max Planck Institute For Pflanzenzuchtungsforschung
Current Opinion in Plant Biology | Year: 2010

The sessile nature of flowering plants and their capacity to thrive in soil habitats likely resulted in specific adaptation mechanisms enabling co-existence with a vast diversity of air-borne and soil-borne microorganisms. Only a small fraction of these microbial encounters result in pathogenic or symbiotic interactions, whilst the majority appear to give rise to commensalistic or mutualistic associations. Considering the abundance of the latter associations the question arises whether plants evolved, besides the plant immune system, other dedicated mechanisms to communicate with and to host microbial communities in the phyllosphere and rhizosphere. We hypothesize that the constitutive and microbe-induced secretion of specialized plant-derived biomolecules creates a critical interface for all types of plant-microbe associations. Thus, the plant secretory machinery might serve an important role in establishing an extended phenotype with microbial life. © 2010 Elsevier Ltd.


Rushton P.J.,South Dakota State University | Somssich I.E.,Max Planck Institute For Pflanzenzuchtungsforschung | Ringler P.,University of Nevada, Las Vegas | Shen Q.J.,University of Nevada, Las Vegas
Trends in Plant Science | Year: 2010

WRKY transcription factors are one of the largest families of transcriptional regulators in plants and form integral parts of signalling webs that modulate many plant processes. Here, we review recent significant progress in WRKY transcription factor research. New findings illustrate that WRKY proteins often act as repressors as well as activators, and that members of the family play roles in both the repression and de-repression of important plant processes. Furthermore, it is becoming clear that a single WRKY transcription factor might be involved in regulating several seemingly disparate processes. Mechanisms of signalling and transcriptional regulation are being dissected, uncovering WRKY protein functions via interactions with a diverse array of protein partners, including MAP kinases, MAP kinase kinases, 14-3-3 proteins, calmodulin, histone deacetylases, resistance proteins and other WRKY transcription factors. WRKY genes exhibit extensive autoregulation and cross-regulation that facilitates transcriptional reprogramming in a dynamic web with built-in redundancy. © 2010 Elsevier Ltd. All rights reserved.

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