Principles and characteristics of the Arabidopsis WRKY regulatory network during early MAMP-triggered immunity.

During microbe-associated molecular pattern-triggered immunity more than 5000 Arabidopsis genes are significantly altered in their expression, and the question arises, how such an enormous reprogramming of the transcriptome can be regulated in a safe and robust manner? For the WRKY transcription factors (TFs), which are important regulators of numerous defense responses, it appears that they act in a complex regulatory sub-network rather than in a linear fashion, which would be much more vulnerable to gene function loss either by pathogen-derived effectors or by mutations. In this study we employed RNA-seq, mass spectrometry and chromatin immunoprecipitation-seq to find evidence for and uncover principles and characteristics of this network. Upon flg22-treatment, one can distinguish between two sets of WRKY genes: constitutively expressed and induced WRKY genes.

Botrytis cinerea B05.10 promotes disease development in Arabidopsis by suppressing WRKY33-mediated host immunity.

The large WRKY transcription factor family is mainly involved in regulating plant immune responses. Arabidopsis WRKY33 is a key transcriptional regulator of hormonal and metabolic processes towards Botrytis cinerea strain 2100 infection and is essential for resistance. In contrast to B.

Transcriptional events defining plant immune responses.

Rapid and massive transcriptional reprogramming upon pathogen recognition is the decisive step in plant-phytopathogen interactions. Plant transcription factors (TFs) are key players in this process but they require a suite of other context-specific co-regulators to establish sensory transcription regulatory networks to bring about host immunity. Molecular, genetic and biochemical studies, particularly in the model plants Arabidopsis and rice, are continuously uncovering new components of the transcriptional machinery that can selectively impact host resistance toward a diverse range of pathogens.

Induced Genome-Wide Binding of Three Arabidopsis WRKY Transcription Factors during Early MAMP-Triggered Immunity.

During microbial-associated molecular pattern-triggered immunity (MTI), molecules derived from microbes are perceived by cell surface receptors and upon signaling to the nucleus initiate a massive transcriptional reprogramming critical to mount an appropriate host defense response. WRKY transcription factors play an important role in regulating these transcriptional processes. Here, we determined on a genome-wide scale the flg22-induced in vivo DNA binding dynamics of three of the most prominent WRKY factors, WRKY18, WRKY40, and WRKY33.

Negative regulation of ABA signaling by WRKY33 is critical for Arabidopsis immunity towards Botrytis cinerea 2100.

The Arabidopsis mutant wrky33 is highly susceptible to Botrytis cinerea. We identified >1680 Botrytis-induced WRKY33 binding sites associated with 1576 Arabidopsis genes. Transcriptional profiling defined 318 functional direct target genes at 14 hr post inoculation.

Functional dissection of the PROPEP2 and PROPEP3 promoters reveals the importance of WRKY factors in mediating microbe-associated molecular pattern-induced expression.

· In Arabidopsis thaliana, small peptides (AtPeps) encoded by PROPEP genes act as damage-associated molecular patterns (DAMPs) that are perceived by two leucine-rich repeat receptor kinases, PEPR1 and PEPR2, to amplify defense responses. In particular, expression of PROPEP2 and PROPEP3 is strongly and rapidly induced by AtPeps, in response to bacterial, oomycete, and fungal pathogens, and microbe-associated molecular patterns (MAMPs). · The cis-regulatory modules (CRMs) within the PROPEP2 and PROPEP3 promoters that mediate MAMP responsiveness were delineated, employing parsley (Petroselinum crispum) protoplasts and transgenic A.

Arabidopsis WRKY33 is a key transcriptional regulator of hormonal and metabolic responses toward Botrytis cinerea infection.

The Arabidopsis (Arabidopsis thaliana) transcription factor WRKY33 is essential for defense toward the necrotrophic fungus Botrytis cinerea. Here, we aimed at identifying early transcriptional responses mediated by WRKY33. Global expression profiling on susceptible wrky33 and resistant wild-type plants uncovered massive differential transcriptional reprogramming upon B.

Transcriptional plant responses critical for resistance towards necrotrophic pathogens.

Plant defenses aimed at necrotrophic pathogens appear to be genetically complex. Despite the apparent lack of a specific recognition of such necrotrophs by products of major R genes, biochemical, molecular, and genetic studies, in particular using the model plant Arabidopsis, have uncovered numerous host components critical for the outcome of such interactions. Although the JA signaling pathway plays a central role in plant defense toward necrotrophs additional signaling pathways contribute to the plant response network.

Conserved functions of Arabidopsis and rice CC-type glutaredoxins in flower development and pathogen response.

Glutaredoxins (GRXs) are ubiquitous oxidoreductases that play a crucial role in response to oxidative stress by reducing disulfides in various organisms. In planta, three different GRX classes have been identified according to their active site motifs. CPYC and CGFS classes are found in all organisms, whereas the CC-type class is specific for higher land plants.

Studies on DNA-binding selectivity of WRKY transcription factors lend structural clues into WRKY-domain function.

WRKY transcription factors have been shown to play a major role in regulating, both positively and negatively, the plant defense transcriptome. Nearly all studied WRKY factors appear to have a stereotypic binding preference to one DNA element termed the W-box. How specificity for certain promoters is accomplished therefore remains completely unknown.

Expression of AtWRKY33 encoding a pathogen- or PAMP-responsive WRKY transcription factor is regulated by a composite DNA motif containing W box elements.

WRKY transcription factors regulate distinct parts of the plant defense transcriptome. Expression of many WRKY genes themselves is induced by pathogens or pathogen-mimicking molecules. Here, we demonstrate that Arabidopsis WRKY33 responds to various stimuli associated with plant defense as well as to different kinds of phytopathogens.

The miRNA156/157 recognition element in the 3' UTR of the Arabidopsis SBP box gene SPL3 prevents early flowering by translational inhibition in seedlings.

miRNAs are a class of versatile small RNAs that control gene expression post-transcriptionally, governing many facets of plant cell functions. They interact with their target mRNA at a site of sequence complementarity and modulate their expression levels. Here, we provide evidence, based on transient assays and stable transgenic lines, that the 3' UTR of the Arabidopsis SBP box gene SPL3 contains a functional miRNA-responsive element (MRE) that is complementary to miR156 and miRNA157.

An improved method for preparing Agrobacterium cells that simplifies the Arabidopsis transformation protocol.

Background: The Agrobacterium vacuum (Bechtold et al 1993) and floral-dip (Clough and Bent 1998) are very efficient methods for generating transgenic Arabidopsis plants. These methods allow plant transformation without the need for tissue culture. Large volumes of bacterial cultures grown in liquid media are necessary for both of these transformation methods.

Characterization of crystals of the Hjc resolvase from Archaeoglobus fulgidus grown in gel by counter-diffusion.

Holliday junction-resolving enzymes are ubiquitous proteins that play a key role in DNA repair and reorganization by homologous recombination. The Holliday junction-cutting enzyme (Hjc) from the archaeon Archaeoglobus fulgidus is a member of this group. The first Hjc crystals were obtained by conventional sparse-matrix screening.

A regulator of nutritional copper signaling in Chlamydomonas is an SBP domain protein that recognizes the GTAC core of copper response element.

The CRR1 (Copper Response Regulator) locus, required for both activating and repressing target genes of a copper- and hypoxia-sensing pathway in Chlamydomonas, encodes a 1,232-residue candidate transcription factor with a plant-specific DNA-binding domain named SBP, ankyrin repeats, and a C-terminal Cys-rich region, with similarity to a Drosophila metallothionein. The recombinant SBP domain of Crr1 shows zinc-dependent binding to functionally defined copper-response elements associated with the CYC6 and CPX1 promoters that contain a critical GTAC core sequence. Competition experiments indicate equivalent selectivity for copper-response elements from either promoter and 10-fold greater selectivity for the wild-type sequence vs.

Functional dissection of the plant-specific SBP-domain: overlap of the DNA-binding and nuclear localization domains.

SBP-domain proteins are plant-specific putative transcription factors. They all contain the highly conserved 76 amino acid residue SBP-domain, shown to bind specifically to related motifs in the Antirrhinum majus SQUA promoter and the orthologous Arabidopsis thaliana AP1 promoter. The structural basis for this sequence-specific binding of DNA are two Zn-finger like structures formed by the coordination of two zinc ions by conserved cysteine and histidine residues.

Holliday junction-resolving enzymes from eight hyperthermophilic archaea differ in reactions with cruciform DNA.

Holliday junction-resolving enzymes have been identified in a broad variety of organisms and tissues. In this study, six new Holliday junction-cleaving enzymes (Hjcs) were obtained from hyperthermophilic crenarchaeal and euryarchaeal species, including Pyrococcus horikoshii, Pyrococcus abyssi, Methanococcus jannaschii, Methanobacterium thermautotrophicum, Archaeoglobus fulgidus, and Aeropyrum pernix. The genes were cloned and overexpressed in Escherichia coli, and the respective proteins were purified from crude extracts to homogeneity.

High affinity of endonuclease VII for the Holliday structure containing one nick ensures productive resolution.

During homologous recombination, genetic information is physically exchanged between parental DNAs via crossing single strands of the same polarity within a four-way DNA junction called a Holliday structure. This process is terminated by the endonucleolytic activity of resolvases, which convert the four-way DNA back to two double strands. To achieve productive resolution, the two subunits of the dimeric enzymes introduce two single-strand cuts positioned symmetrically in opposite strands across the DNA junction.