Differential response of etiolated pea seedlings to inoculation with rhizobacteria capable of utilizing 1-aminocyclopropane-1-carboxylate or L-methionine

The majority of soil microorganisms can derive ethylene from L-methionine (L-MET), while some rhizobacteria can hydrolyze 1-aminocyclopropane-1-carboxylate (ACC) due to their ACC-deaminase activity. In this study, three strains having either ACC-deaminase activity (Pseudomonas putida biotype A, A7), or the ability to produce ethylene from L-MET (Acinetobacter calcoaceticus, M9) or both (Pseudomonas fluorescens, AM3) were used for inoculation. The highly ethylene specific bioassay of a classical "triple" response in pea seedlings was used to investigate the effect of the inoculation with the rhizobacteria in the presence of 10 mM ACC or L-MET. The exogenous application of ACC had a concentration-dependent effect on the etiolated pea seedlings in creating the classical "triple" response. The inoculation with P. putida diluted the effect of ACC, which was most likely due to its ACC-deaminase activity. Similarly, the application of Co2+ reduced the ACC-imposed effect on etiolated pea seedlings. In contrast, the inoculation of A. calcoaceticus or P. fluorescens in the presence of L-MET caused a stronger classical "triple" response in etiolated pea seedlings; most likely by producing ethylene from L-MET. This is the first study, to our knowledge, reporting on the comparative effect of rhizobacteria capable of utilizing ACC vs L-MET on etiolated pea seedlings.     

A surface acoustic wave sensor functionalized with a polypyrrole molecularly imprinted polymer for selective dopamine detection

A surface acoustic wave sensor operating at 104 MHz and functionalized with a polypyrrole molecularly imprinted polymer has been designed for selective detection of dopamine (DA). Optimization of pyrrole/DA ratio, polymerization and immersion times permitted to obtain a highly selective sensor, which has a sensitivity of 0.55°/mM (≈550 Hz/mM) and a detection limit of ≈ 10 nM. Morphology and related roughness parameters of molecularly imprinted polymer surfaces, before and after extraction of DA, as well as that of the non imprinted polymer were characterized by atomic force microscopy. The developed chemosensor selectively recognized dopamine over the structurally similar compound 4‐hydroxyphenethylamine (referred as tyramine), or ascorbic acid,which co‐exists with DA in body fluids at a much higher concentration. Selectivity tests were also carried out with dihydroxybenzene, for which an unexpected phase variation of order of 75% of the DA one was observed. Quantum chemical calculations, based on the density functional theory, were carried out to determine the nature of interactions between each analyte and the PPy matrix and the DA imprinted PPy polypyrrole sensing layer in order to account for the important phase variation observed during dihydroxybenzene injection. Copyright © 2015 John Wiley & Sons, Ltd.     

Relationships between gas-exchange characteristics and stomatal structural modifications in some desert grasses under high salinity

Two populations, one from lesser saline Derawar Fort (DF) and the other from highly saline Ladam Sir (LS) in the Cholistan desert, for each of the five grass species, Aeluropus lagopoides, Cymbopogon jwarancusa, Lasiurus scindicus, Ochthochloa compressa, and Sporobolus ioclados were examined to investigate the influence of salinity on structural and functional characteristics of stomata. Salinity tolerance in A. lagopoides mainly depended on controlled transpiration rate (E) and high water-use efficiency (WUE), which was found to be regulated by fewer and smaller stomata on both leaf surfaces as well as stomatal encryption by epidermal invaginations. C. jwarancusa had sunken stomata on the abaxial surface only, which largely reflected a reduced E, but less affected stomatal conductance (g _s) or WUE. L. scindicus had fewer but larger stomata along with hairs/trichomes which may function to avoid water loss through transpiration, and hence, to attain a high WUE. In O. compressa stomata were found only on the abaxial surface and these were completely encrypted by epidermal invaginations as well as a dense covering of microhairs, which was associated with a low E and high WUE under salinity stress. In S. ioclados, the traits of increased stomatal density and decreased stomatal area may be critical for stomatal regulation under salt-prone environments. High stomatal regulation depended largely on stomatal density, area, and degree of encryption under salinity, which is of great ecophysiological significance for plants growing under osmotic stresses.     

Anillin and the septins promote asymmetric ingression of the cytokinetic furrow

During cytokinesis, constriction of a cortical contractile ring generates a furrow that partitions one cell into two. The contractile ring contains three filament systems: actin, bipolar myosin II filaments, and septins, GTP-binding hetero-oligomers that polymerize to form a membrane-associated lattice. The contractile ring also contains a potential filament crosslinker, Anillin, that binds all three filament types. Here, we show that the contractile ring possesses an intrinsic symmetry-breaking mechanism that promotes asymmetric furrowing. Asymmetric ingression requires Anillin and the septins, which promote the coalescence of components on one side of the contractile ring, but is insensitive to a 10-fold reduction in myosin II levels. When asymmetry is disrupted, cytokinesis becomes sensitive to partial inhibition of contractility. Thus, asymmetric furrow ingression, a prevalent but previously unexplored feature of cell division in metazoans, is generated by the action of two conserved furrow components and serves a mechanical function that makes cytokinesis robust.     

Enzymatic condensation of dopamine and acetaldehyde: a salsolinol synthase from rat brain

Salsolinol (1-methyl-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline; Sal) is structurally similar to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine, which is supposed to have a role in the development of Parkinson-like syndrome in both human and non-human subjects. In the human brain, the amount of (R)-enantiomer of Sal is much higher than (S)-enantiomer, suggesting that a putative enzyme may participate in the synthesis of (R)-salsolinol, called (R)-salsolinol synthase. In this study, the (R)-salsolinol synthase activity in the condensation of dopamine and acetaldehyde was investigated in the crude extracts from the brains of Sprague Dawley rats. Identification of the enzymatic reaction products and enzyme activity detection were achieved by HPLC-electrochemical detection. The discovery of this enzyme activity in rat’s brain indicates the natural existence of (R)-salsolinol synthase in the brains of humans and rats, and it is distributed in most brain regions of rat with higher activity in soluble proteins extracted from striatum and substantia nigra.     

Analysis of microtubule polymerization in vitro and during the cell cycle in Xenopus egg extracts

Microtubules are dynamic polymers that participate in multiple cellular processes such as vesicular transport and cell division. Microtubule dynamics alter dramatically during the cell cycle. An excellent system to study microtubule dynamics is Xenopus egg extracts since it is a system that is open to manipulation. The extracts can be cycled between mitosis and interphase allowing the study of microtubules in these phases as well as during cell cycle transitions. Here, we provide simple assays to study microtubules in extracts and in vitro using purified components. Protocols are provided for the purification of frog tubulin, microtubule pelleting from extracts and in vitro, assembly of microtubule structures in extracts, and isolation of microtubule-associated proteins from extract. These methods can be used to analyze the effect of a protein of interest on the microtubule cytoskeleton.     

Induction of Apoptosis and Antiproliferative Activity of Naringenin in Human Epidermoid Carcinoma Cell through ROS Generation and Cell Cycle Arrest

A natural predominant flavanone naringenin, especially abundant in citrus fruits, has a wide range of pharmacological activities. The search for antiproliferative agents that reduce skin carcinoma is a task of great importance. The objective of this study was to analyze the anti-proliferative and apoptotic mechanism of naringenin using MTT assay, DNA fragmentation, nuclear condensation, change in mitochondrial membrane potential, cell cycle kinetics and caspase-3 as biomarkers and to investigate the ability to induce reactive oxygen species (ROS) initiating apoptotic cascade in human epidermoid carcinoma A431 cells. Results showed that naringenin exposure significantly reduced the cell viability of A431 cells (p<0.01) with a concomitant increase in nuclear condensation and DNA fragmentation in a dose dependent manner. The intracellular ROS generation assay showed statistically significant (p<0.001) dose-related increment in ROS production for naringenin. It also caused naringenin-mediated epidermoid carcinoma apoptosis by inducing mitochondrial depolarization. Cell cycle study showed that naringenin induced cell cycle arrest in G₀/G₁ phase of cell cycle and caspase-3 analysis revealed a dose dependent increment in caspase-3 activity which led to cell apoptosis. This study confirms the efficacy of naringenin that lead to cell death in epidermoid carcinoma cells via inducing ROS generation, mitochondrial depolarization, nuclear condensation, DNA fragmentation, cell cycle arrest in G₀/G₁ phase and caspase-3 activation.