Infestation by a Common Parasite is Correlated with Ant Symbiont Identity in a Plant‐Ant Mutualism

In East Africa, up to four symbiotic ant species associate with the obligate myrmecophyte Acacia drepanolobium. These ant species differ in the extent to which they defend their host trees from both vertebrate and invertebrate herbivores, but other potential roles of ants in tree defense have not been studied. We investigate the distribution of a new species of parasitic midge targeting A. drepanolobium in a region where A. drepanolobium is inhabited almost exclusively by two ant species—Crematogaster nigriceps and C. mimosae. We find that the frequency of infestation correlates strongly with the identity of the ant occupant: trees inhabited by C. nigriceps are significantly less likely to be infested with parasitic midges. Although the two ant species responded similarly to simulated large herbivore disturbances, trees inhabited by C. nigriceps also had a lower invertebrate load than trees inhabited by C. mimosae. We suggest that differences in defensive behavior towards invertebrates could be one explanation of the observed differences in infestation of A. drepanolobium by parasitic midges.     

DYNAMIN-RELATED PROTEIN DRP1A functions with DRP2B in plant growth,flg22-immune responses,and endocytosis

Ligand-induced endocytosis of the immune receptor FLAGELLIN SENSING2 (FLS2) is critical for maintaining its proper abundance in the plasma membrane (PM) to initiate and subsequently down regulate cellular immune responses to bacterial flagellin or flg22-peptide. The molecular components governing PM abundance of FLS2, however, remain mostly unknown. Here, we identified Arabidopsis (Arabidopsis thaliana) DYNAMIN-RELATED PROTEIN1A (DRP1A), a member of a plant-specific family of large dynamin GTPases, as a critical contributor to ligand-induced endocytosis of FLS2 and its physiological roles in flg22-signaling and immunity against Pseudomonas syringae pv. tomato DC3000 bacteria in leaves. Notably, drp1a single mutants displayed similar flg22-defects as those previously reported for mutants in another dynamin-related protein, DRP2B, that was previously shown to colocalize with DRP1A. Our study also uncovered synergistic roles of DRP1A and DRP2B in plant growth and development as drp1a drp2b double mutants exhibited severely stunted roots and cotyledons, as well as defective cell shape, cytokinesis, and seedling lethality. Furthermore, drp1a drp2b double mutants hyperaccumulated FLS2 in the PM prior to flg22-treatment and exhibited a block in ligand-induced endocytosis of FLS2, indicating combinatorial roles for DRP1A and DRP1B in governing PM abundance of FLS2. However, the increased steady-state PM accumulation of FLS2 in drp1a drp2b double mutants did not result in increased flg22 responses. We propose that DRP1A and DRP2B are important for the regulation of PM-associated levels of FLS2 necessary to attain signaling competency to initiate distinct flg22 responses, potentially through modulating the lipid environment in defined PM domains.

A plant-specific large dynamin GTPase is required for plant responses against bacterial pathogens and, with another dynamin, regulates the cell surface composition for plant growth and defense.     

Loss of miR-203 regulates cell shape and matrix adhesion through ROBO1/Rac/FAK in response to stiffness

Breast tumor progression is accompanied by changes in the surrounding extracellular matrix (ECM) that increase stiffness of the microenvironment. Mammary epithelial cells engage regulatory pathways that permit dynamic responses to mechanical cues from the ECM. Here, we identify a SLIT2/ROBO1 signaling circuit as a key regulatory mechanism by which cells sense and respond to ECM stiffness to preserve tensional homeostasis. We observed that Robo1 ablation in the developing mammary gland compromised actin stress fiber assembly and inhibited cell contractility to perturb tissue morphogenesis, whereas SLIT2 treatment stimulated Rac and increased focal adhesion kinase activity to enhance cell tension by maintaining cell shape and matrix adhesion. Further investigation revealed that a stiff ECM increased Robo1 levels by down-regulating miR-203. Consistently, patients whose tumor expressed a low miR-203/high Robo1 expression pattern exhibited a better overall survival prognosis. These studies show that cells subjected to stiffened environments up-regulate Robo1 as a protective mechanism that maintains cell shape and facilitates ECM adherence.     

Enhanced bioproduction of anticancer precursor vindoline by yeast cell factories

The pharmaceutical industry faces a growing demand and recurrent shortages in many anticancer plant drugs given their extensive use in human chemotherapy. Efficient alternative strategies of supply of these natural products such as bioproduction by microorganisms are needed to ensure stable and massive manufacturing. Here, we developed and optimized yeast cell factories efficiently converting tabersonine to vindoline, a precursor of the major anticancer alkaloids vinblastine and vincristine. First, fine-tuning of heterologous gene copies restrained side metabolites synthesis towards vindoline production. Tabersonine to vindoline bioconversion was further enhanced through a rational medium optimization (pH, composition) and a sequential feeding strategy. Finally, a vindoline titre of 266 mg l⁻¹ (88% yield) was reached in an optimized fed-batch bioreactor. This precursor-directed synthesis of vindoline thus paves the way towards future industrial bioproduction through the valorization of abundant tabersonine resources.     

Production of methylparaben in Escherichia coli

Journal of Industrial Microbiology & Biotechnology - Since the 1930s, parabens have been employed widely as preservatives in food, pharmaceutical, and personal care products. These alkyl esters...     

Transport of sulfate in the rabbit's brain

The possibility that, in the rabbit, sulfate is actively transported across the choroid plexuses was investigated by ventriculo-cisternal perfusion in the absence and presence of carrier. No evidence for this could be found. Penetration of sulfate from blood to brain and CSF was measured in the intact animal equilibration was very slow, indicating the presence of high barriers for this solute, but the low steady-state level in the brain, approached in these experiments, was quite consistent with slow passive permeability aacross the barriers, with free exchange between extracellular fluid and CSF. The clearance of another slowly penetrating solute, creatinine, from the perfusion fluid during ventriculo-cisternal perfusion was comparabl with that of sulfate.     

Observation of nanosecond transient states in laser-induced reactions of pyridoxal 5′-phosphate

A nanosecond laser-flash photolysis system is described. The intensity of the 5-ns resolved pulses of the analyzing flash can be digitized with 0.03% precision. As a result, the electronic absorption spectra of transients in 60-μl samples of 10^?4m enzyme have been determined.     

Succinate as anin vitro electron donor for the particulate methane mono-oxygenase ofMethylosinus trichosporium OB3b

Summary Relief of copper deficiency during growth promotes the proliferation of intracytoplasmic membranes together with synthesis of particulate methane mono-oxgenase (MMC) inMethylosinus trichosporium OB3b. Particulate MMO functionsin vitro (in cell-free extracts and membrane preparations) with either succinate or NADH as electron donor but soluble MMO functions only with NADH.