Berberine Bridge Enzyme-like Oligosaccharide Oxidases Act as Enzymatic Transducers Between Microbial Glycoside Hydrolases and Plant Peroxidases.

Oligogalacturonide (OG)-oxidase 1 (OGOX1) and cellodextrin (CD)-oxidase (CELLOX) are plant berberine bridge enzyme-like oligosaccharide oxidases that oxidize OGs and CDs, cell-wall fragments with the nature of damage-associated molecular patterns. The oxidation of OGs and CDs attenuates their elicitor activity and concomitantly releases HO. By using a multiple enzyme-based assay, we demonstrate that the HO generated downstream of the combined action between a fungal polygalacturonase and OGOX1 or an endoglucanase and CELLOX can be directed by plant peroxidases (PODs) either towards a reaction possibly involved in plant defense, such as the oxidation of monolignol or a reaction possibly involved in a developmental event, such as the oxidation of auxin (indole-3-acetic acid), pointing to OGOX1 and CELLOX as enzymatic transducers between microbial glycoside hydrolases and plant PODs.

Plant immunity by damage-associated molecular patterns (DAMPs).

Recognition by plant receptors of microbe-associated molecular patterns (MAMPs) and pathogenicity effectors activates immunity. However, before evolving the capacity of perceiving and responding to MAMPs and pathogenicity factors, plants, like animals, must have faced the necessity to protect and repair the mechanical wounds used by pathogens as an easy passage into their tissue. Consequently, plants evolved the capacity to react to damage-associated molecular patterns (DAMPs) with responses capable of functioning also in the absence of pathogens.

The intracellular ROS accumulation in elicitor-induced immunity requires the multiple organelle-targeted Arabidopsis NPK1-related protein kinases.

Recognition at the plasma membrane of danger signals (elicitors) belonging to the classes of the microbe/pathogen- and damage-associated molecular patterns is a key event in pathogen sensing by plants and is associated with a rapid activation of immune responses. Different cellular compartments, including plasma membrane, chloroplasts, nuclei and mitochondria, are involved in the immune cellular program. However, how pathogen sensing is transmitted throughout the cell remains largely to be uncovered.

An EFR-Cf-9 chimera confers enhanced resistance to bacterial pathogens by SOBIR1- and BAK1-dependent recognition of elf18.

The transfer of well-studied native and chimeric pattern recognition receptors (PRRs) to susceptible plants is a proven strategy to improve host resistance. In most cases, the ectodomain determines PRR recognition specificity, while the endodomain determines the intensity of the immune response. Here we report the generation and characterization of the chimeric receptor EFR-Cf-9, which carries the ectodomain of the Arabidopsis thaliana EF-Tu receptor (EFR) and the endodomain of the tomato Cf-9 resistance protein.

An Arabidopsis berberine bridge enzyme-like protein specifically oxidizes cellulose oligomers and plays a role in immunity.

The plant cell wall is the barrier that pathogens must overcome to cause a disease, and to this end they secrete enzymes that degrade the various cell wall components. Due to the complexity of these components, several types of oligosaccharide fragments may be released during pathogenesis and some of these can act as damage-associated molecular patterns (DAMPs). Well-known DAMPs are the oligogalacturonides (OGs) released upon degradation of homogalacturonan and the products of cellulose breakdown, i.

Cell wall traits that influence plant development, immunity, and bioconversion.

The architecture of the plant cell wall is highly dynamic, being substantially re-modeled during growth and development. Cell walls determine the size and shape of cells and contribute to the functional specialization of tissues and organs. Beyond the physiological dynamics, the wall structure undergoes changes upon biotic or abiotic stresses.

Corrigendum: Loss of the Arabidopsis Protein Kinases ANPs Affects Root Cell Wall Composition, and Triggers the Cell Wall Damage Syndrome.

[This corrects the article DOI: 10.3389/fpls.2017.

Loss of the Arabidopsis Protein Kinases ANPs Affects Root Cell Wall Composition, and Triggers the Cell Wall Damage Syndrome.

The Arabidopsis NPK1-related Protein kinases ANP1, ANP2 and ANP3 belong to the MAP kinase kinase kinase (MAPKKK) superfamily and were previously described to be crucial for cytokinesis, elicitor-induced immunity and development. Here we investigate the basis of their role in development by using conditional β-estradiol-inducible triple mutants to overcome lethality. In seedlings, lack of ANPs causes root cell bulging, with the transition zone being the most sensitive region.

Four Arabidopsis berberine bridge enzyme-like proteins are specific oxidases that inactivate the elicitor-active oligogalacturonides.

Recognition of endogenous molecules acting as 'damage-associated molecular patterns' (DAMPs) is a key feature of immunity in both animals and plants. Oligogalacturonides (OGs), i.e.

Immune responses induced by oligogalacturonides are differentially affected by AvrPto and loss of BAK1/BKK1 and PEPR1/PEPR2.

Plants possess an innate immune system capable of restricting invasion by most potential pathogens. At the cell surface, the recognition of microbe-associated molecular patterns (MAMPs) and/or damage-associated molecular patterns (DAMPs) by pattern recognition receptors (PRRs) represents the first event for the prompt mounting of an effective immune response. Pathogens have evolved effectors that block MAMP-triggered immunity.

GRP-3 and KAPP, encoding interactors of WAK1, negatively affect defense responses induced by oligogalacturonides and local response to wounding.

Conserved microbe-associated molecular patterns (MAMPs) and damage-associated molecular patterns (DAMPs) act as danger signals to activate the plant immune response. These molecules are recognized by surface receptors that are referred to as pattern recognition receptors. Oligogalacturonides (OGs), DAMPs released from the plant cell wall homogalacturonan, have also been proposed to act as local signals in the response to wounding.

Sensitive detection and measurement of oligogalacturonides in Arabidopsis.

Oligogalacturonides (OGs) are pectin fragments derived from the partial hydrolysis of the plant cell wall pectin; they are elicitors of various defense responses. While their activity is well documented, the detection of OGs produced in planta is still a challenging task. A protocol has been developed for the extraction and analysis of OGs from small samples of Arabidopsis tissues by using fluorescent labeled OGs, which allowed to monitor the efficiency of extraction.

Plant immunity triggered by engineered in vivo release of oligogalacturonides, damage-associated molecular patterns.

Oligogalacturonides (OGs) are fragments of pectin that activate plant innate immunity by functioning as damage-associated molecular patterns (DAMPs). We set out to test the hypothesis that OGs are generated in planta by partial inhibition of pathogen-encoded polygalacturonases (PGs). A gene encoding a fungal PG was fused with a gene encoding a plant polygalacturonase-inhibiting protein (PGIP) and expressed in transgenic Arabidopsis plants.

How do pectin methylesterases and their inhibitors affect the spreading of tobamovirus?

After replication in the cytoplasm, viruses spread from the infected cell into the neighboring cells through plasmodesmata, membranous channels embedded by the cell wall. As obligate parasites, viruses have acquired the ability to utilize host factors that unwillingly cooperate for the viral infection process. For example, the viral movement proteins (MP) interacts with the host pectin methylesterase (PME) and both proteins cooperate to sustain the viral spread.

Wounding in the plant tissue: the defense of a dangerous passage.

Plants are continuously exposed to agents such as herbivores and environmental mechanical stresses that cause wounding and open the way to the invasion by microbial pathogens. Wounding provides nutrients to pathogens and facilitates their entry into the tissue and subsequent infection. Plants have evolved constitutive and induced defense mechanisms to properly respond to wounding and prevent infection.

Controlled expression of pectic enzymes in Arabidopsis thaliana enhances biomass conversion without adverse effects on growth.

Lignocellulosic biomass from agriculture wastes is a potential source of biofuel, but its use is currently limited by the recalcitrance of the plant cell wall to enzymatic digestion. Modification of the wall structural components can be a viable strategy to overcome this bottleneck. We have previously shown that the expression of a fungal polygalacturonase (pga2 from Aspergillus niger) in Arabidopsis and tobacco plants reduces the levels of de-esterified homogalacturonan in the cell wall and significantly increases saccharification efficiency.

A lower content of de-methylesterified homogalacturonan improves enzymatic cell separation and isolation of mesophyll protoplasts in Arabidopsis.

Cell adhesion occurs primarily at the level of middle lamella which is mainly composed by pectin polysaccharides. These can be degraded by cell wall degrading enzymes (CWDEs) during developmental processes to allow a controlled separation of plant cells. Extensive cell wall degradation by CWDEs with consequent cell separation is performed when protoplasts are isolated from plant tissues by using mixtures of CWDEs.