Dynamin-Related Protein AtDRP2A Contributes to Late Flg22-Signaling and Effective Immunity Against Bacteria.

In eukaryotes, dynamins and dynamin-related proteins (DRPs) are high-molecular weight GTPases responsible for mechanochemical fission of organelles or membranes. Of the six DRP subfamilies in , AtDRP1 and AtDRP2 family members serve as endocytic accessory proteins in clathrin-mediated endocytosis. Most studies have focused on AtDRP1A and AtDRP2B as critical modulators of plant pattern-triggered immunity (PTI) against pathogenic, flagellated pv.

Ligand-induced monoubiquitination of BIK1 regulates plant immunity.

Recognition of microbe-associated molecular patterns (MAMPs) by pattern recognition receptors (PRRs) triggers the first line of inducible defence against invading pathogens. Receptor-like cytoplasmic kinases (RLCKs) are convergent regulators that associate with multiple PRRs in plants. The mechanisms that underlie the activation of RLCKs are unclear.

Quantitative Analysis of Ligand-Induced Endocytosis of FLAGELLIN-SENSING 2 Using Automated Image Segmentation.

Plants are equipped with a suite of plant pattern recognition receptors (PRRs) that must be properly trafficked to and from the plasma membrane (PM), which serves as the host-pathogen interface, for robust detection of invading pathogenic microbes. Recognition of bacterial flagellin, or the derived peptide flg22, is facilitated by the PM-localized PRR, FLAGELLIN SENSING 2 (FLS2). Upon flg22 binding, FLS2 is rapidly internalized from the PM into endosomal compartments and subsequently degraded.

Simplified Enrichment of Plasma Membrane Proteins from Arabidopsis thaliana Seedlings Using Differential Centrifugation and Brij-58 Treatment.

The plasma membrane (PM) forms a barrier between a plant cell and its environment. Proteins at this subcellular location play diverse and complex roles, including perception of extracellular signals to coordinate cellular changes. Analyses of PM proteins, however, are often limited by the relatively low abundance of these proteins in the total cellular protein pool.

Increased callose deposition in plants lacking DYNAMIN-RELATED PROTEIN 2B is dependent upon POWDERY MILDEW RESISTANT 4.

Callose deposition within the cell wall is a well-documented plant immune response to pathogenic organisms as well as to pathogen-/microbe- associated molecular patterns (P/MAMPs). However, the molecular mechanisms that modulate pathogen-induced callose deposition are less understood. We reported previously that Arabidopsis plants lacking the vesicle trafficking component DYNAMIN-RELATED PROTEIN 2B (DRP2B) display increased callose deposition in response to the PAMP flg22.

Loss of Arabidopsis thaliana Dynamin-Related Protein 2B reveals separation of innate immune signaling pathways.

Vesicular trafficking has emerged as an important means by which eukaryotes modulate responses to microbial pathogens, likely by contributing to the correct localization and levels of host components necessary for effective immunity. However, considering the complexity of membrane trafficking in plants, relatively few vesicular trafficking components with functions in plant immunity are known. Here we demonstrate that Arabidopsis thaliana Dynamin-Related Protein 2B (DRP2B), which has been previously implicated in constitutive clathrin-mediated endocytosis (CME), functions in responses to flg22 (the active peptide derivative of bacterial flagellin) and immunity against flagellated bacteria Pseudomonas syringae pv.

A re-elicitation assay to correlate flg22-signaling competency with ligand-induced endocytic degradation of the FLS2 receptor.

In the model plant Arabidopsis, the best studied Pattern-triggered immunity (PTI) system is perception of the bacterial pathogen-associated molecular pattern (PAMP) flagellin, or its active peptide-derivative flg22, by the plasma membrane-localized receptor FLAGELLIN SENSING 2 (FLS2). Flg22 perception initiates an array of immune responses including the fast and transient production of reactive oxygen species (ROS). In addition, FLS2 undergoes ligand-induced endocytosis and subsequent degradation within 60 min of flg22-treatment.

Sensitivity to Flg22 is modulated by ligand-induced degradation and de novo synthesis of the endogenous flagellin-receptor FLAGELLIN-SENSING2.

FLAGELLIN-SENSING2 (FLS2) is the plant cell surface receptor that perceives bacterial flagellin or flg22 peptide, initiates flg22-signaling responses, and contributes to bacterial growth restriction. Flg22 elicitation also leads to ligand-induced endocytosis and degradation of FLS2 within 1 h. Why plant cells remove this receptor precisely at the time during which its function is required remains mainly unknown.

NEVERSHED and INFLORESCENCE DEFICIENT IN ABSCISSION are differentially required for cell expansion and cell separation during floral organ abscission in Arabidopsis thaliana.

Floral organ shedding is a cell separation event preceded by cell-wall loosening and generally accompanied by cell expansion. Mutations in NEVERSHED (NEV) or INFLORESCENCE DEFICIENT IN ABSCISSION (IDA) block floral organ abscission in Arabidopsis thaliana. NEV encodes an ADP-ribosylation factor GTPase-activating protein, and cells of nev mutant flowers display membrane-trafficking defects.

CAST AWAY, a membrane-associated receptor-like kinase, inhibits organ abscission in Arabidopsis.

Receptor-like kinase-mediated cell signaling pathways play fundamental roles in many aspects of plant growth and development. A pair of Arabidopsis (Arabidopsis thaliana) leucine-rich repeat receptor-like kinases (LRR-RLKs), HAESA (HAE) and HAESA-LIKE2 (HSL2), have been shown to activate the cell separation process that leads to organ abscission. Another pair of LRR-RLKs, EVERSHED (EVR) and SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE1, act as inhibitors of abscission, potentially by modulating HAE/HSL2 activity.

The SERK1 receptor-like kinase regulates organ separation in Arabidopsis flowers.

Through a sensitized screen for novel components of pathways regulating organ separation in Arabidopsis flowers, we have found that the leucine-rich repeat receptor-like kinase SOMATIC EMBRYOGENESIS RECEPTOR-LIKE KINASE1 (SERK1) acts as a negative regulator of abscission. Mutations in SERK1 dominantly rescue abscission in flowers without functional NEVERSHED (NEV), an ADP-ribosylation factor GTPase-activating protein required for floral organ shedding. We previously reported that the organization of the Golgi apparatus and location of the trans-Golgi network (TGN) are altered in nev mutant flowers.

The EVERSHED receptor-like kinase modulates floral organ shedding in Arabidopsis.

Plant cell signaling triggers the abscission of entire organs, such as fruit, leaves and flowers. Previously, we characterized an ADP-ribosylation factor GTPase-activating protein, NEVERSHED (NEV), that regulates membrane trafficking and is essential for floral organ shedding in Arabidopsis. Through a screen for mutations that restore organ separation in nev flowers, we have identified a leucine-rich repeat receptor-like kinase, EVERSHED (EVR), that functions as an inhibitor of abscission.

Regulation of membrane trafficking and organ separation by the NEVERSHED ARF-GAP protein.

Cell separation, or abscission, is a highly specialized process in plants that facilitates remodeling of their architecture and reproductive success. Because few genes are known to be essential for organ abscission, we conducted a screen for mutations that alter floral organ shedding in Arabidopsis. Nine recessive mutations that block shedding were found to disrupt the function of an ADP-ribosylation factor-GTPase-activating protein (ARF-GAP) we have named NEVERSHED (NEV).

Developmental and cell cycle regulation of the Drosophila histone locus body.

Cyclin E/Cdk2 is necessary for replication-dependent histone mRNA biosynthesis, but how it controls this process in early development is unknown. We show that in Drosophila embryos the MPM-2 monoclonal antibody, raised against a phosphoepitope from human mitotic cells, detects Cyclin E/Cdk2-dependent nuclear foci that colocalize with nascent histone transcripts. These foci are coincident with the histone locus body (HLB), a Cajal body-like nuclear structure associated with the histone locus and enriched in histone pre-mRNA processing factors such as Lsm11, a core component of the U7 small nuclear ribonucleoprotein.

Plant separation: 50 ways to leave your mother.

One of the remarkable features of plants is their ability to shed organs, such as leaves, seeds, flowers, and fruit. Genetic analysis of fruit dehiscence and floral organ shedding in Arabidopsis is revealing the pathways that underlie these distinct separation events. The transcriptional network that patterns the fruit links factors that regulate organ polarity and growth with those that control differentiation of the three cell types that are required for dehiscence.