Involvement of polyamines in the adventitious rooting of micropropagated shoots of the apple rootstock MM106

Apple rootstock MM106 shoots, raised in vitro, rooted at 96.7% after culture on a medium supplemented with an auxin for 5 d in darkness followed by culture on a second medium without growth regulators for 25 d in light. In control conditions (in absence of auxin in the first medium), these shoots did not root. Putrescine (PUT), spermidine (SPD), cyclohexylamine (CHA), and aminoguanidine (AG) enhanced rooting when applied during the first d of culture in the absence of IBA; on the contrary, α-difluoromethylornithine (DFMO) added to the first medium with IBA inhibited rooting. The endogenous levels of indole 3-acetic acid (IAA) and indole 3-acetylaspartic acid (IAAsp) increased up to a maximum concentration at days 2 and 3, respectively, in initial rooting conditions. PUT, when added with IBA, did not affect the typical IAA and IAAsp increase; when applied alone, it provoked an increase of their levels. Similar results were recorded with CHA. SPD, AG, and DFMO did not induce an increase of IAA and IAAsp in nonrooting conditions. The levels of endogenous PUT increased to a maximum at day 2 in rooting conditions; it was slightly affected by exogenous PUT and CHA application but reduced by SPD, AG, and DFMO. In rooting conditions, if the first medium was supplemented with SPD or AG, a small increase in peroxidase activity was observed, similar to that obtained with PUT treatment. The present work indicates an involvement of polyamines in the control of rooting and an interaction with auxins during the physiological phase of rooting. The consequence of this relationship was a different rooting expression, according especially to the content of these regulators in the culture medium.     

Temperature-dependent phase behavior and protein partitioning in giant plasma membrane vesicles

Liquid-ordered (Lo) and liquid-disordered (Ld) phase coexistence has been suggested to partition the plasma membrane of biological cells into lateral compartments, allowing for enrichment or depletion of functionally relevant molecules. This dynamic partitioning might be involved in fine-tuning cellular signaling fidelity through coupling to the plasma membrane protein and lipid composition. In earlier work, giant plasma membrane vesicles, obtained by chemically induced blebbing from cultured cells, were observed to reversibly phase segregate at temperatures significantly below 37 °C. In this contribution, we compare the temperature dependence of fluid phase segregation in HeLa and rat basophilic leukemia (RBL) cells. We find an essentially monotonic temperature dependence of the number of phase-separated vesicles in both cell types. We also observe a strikingly broad distribution of phase transition temperatures in both cell types. The binding of peripheral proteins, such as cholera toxin subunit B (CTB), as well as Annexin V, is observed to modulate phase transition temperatures, indicating that peripheral protein binding may be a regulator for lateral heterogeneity in vivo. The partitioning of numerous signal protein anchors and full length proteins is investigated. We find Lo phase partitioning for several proteins assumed in the literature to be membrane raft associated, but observe deviations from this expectation for other proteins, including caveolin-1.     

Enantiomeric Separation of Original Heterocyclic Organophosphorus Compounds in Supercritical Fluid Chromatography

New and original heterocyclic α-enamido phosphine chiral solutes were prepared: four structurally similar racemates with the chirality center placed on the phosphorus atom, and four other related pairs of enantiomers with chirality borne by the carbon atoms of the phospholane ring. The structural variations were placed on an aliphatic heterocycle (six- or seven-member rings) and on the carbamate function (methyl or t-butyl). Their separation was achieved on a commercial cellulose tris-(3,5-dimethylphenylcarbamate) stationary phase (Lux Cellulose-1, Phenomenex) in supercritical fluid chromatography (SFC). The effects of molecular structure on SFC retention and enantioresolution were studied. Among these eight pairs of enantiomers, some reversal of elution order between similar compounds was observed. The effect of changing the organic solvent (methanol and ethanol) and its proportion (between 5 and 40%) in the mobile phase was investigated. Retention data were collected over the temperature range 0–50 °C, and the results interpreted from thermodynamic aspects. Chirality, 2013. © 2013 Wiley Periodicals, Inc.     

Comparative HPLC Enantioseparation of Thirty‐Six Aromatic Compounds on Four Columns of the Lux® Series: Impact of Substituents,Shapes and Electronic Properties

With the aim to define a combined computational/chromatographic empirical approach useful for the high‐performance liquid chromatography (HPLC) method development of new chiral compounds, 36 racemic aromatic compounds with different chemical structures were used as test probes on four polysaccharide‐based chiral stationary phases (CSPs) of the Lux series, namely Lux Cellulose‐1, Lux Cellulose‐2, Lux Cellulose‐4, and Lux Amylose‐2, using classical n‐hexane/2‐propanol mixtures as mobile phase. Electrostatic potential surfaces (EPSs) determined using Density Functional Theory (DFT) calculations were used to derive size, shape, and electronic properties of each analyte. Then a comparative HPLC screening was carried out in order to evaluate the impact of substituents, shapes, and electronic properties of the analytes on the chromatographic behavior as the column changes. The four CSPs showed good complementary recognition ability. The elution sequence was determined in 30 cases out of 36. The success rate to afford baseline separations (R_s ≥ 1.5) was estimated: 29 compounds out of 36 showed baseline enantioseparation on at least one of the four selected CSPs. The combined computational‐chromatographic screening furnished useful collective structure‐chromatographic behavior relationships and a map of the chiral discrimination abilities of the considered CSPs towards the analytes. On this basis, the chromatographic behavior of new analytes on a set of polysaccharide‐based CSPs can be mapped through the qualitative correlation of chromatographic parameters (k, α, R_s) to computed molecular properties of the analytes. Chirality 25:709–718, 2013. © 2013 Wiley Periodicals, Inc.     

Protein adsorption and transport in cation exchangers with a rigid backbone matrix with and without polymeric surface extenders

We compare the properties and protein adsorption characteristics of two polymeric cation exchangers: UNOsphere S, which has an open macroporous architecture, and Nuvia S, which is based on a very similar backbone matrix but contains sulfonated polymeric surface extenders. A monoclonal IgG and lysozyme were used as model adsorbates. The characteristic pore sizes, determined by inverse size exclusion chromatography, were about 140 nm for UNOsphere S, and only about 10 nm for Nuvia S, indicating that the polymeric extenders occupy a substantial portion of the base matrix pores. Greater exclusion limits were found for Nuvia S in 1 M NaCl and for a similar matrix containing uncharged surface extenders, suggesting that the polymeric extenders collapse partially at high ionic strength or when they are uncharged. Large equilibrium binding capacities were obtained for Nuvia S, approaching 320 ± 10 mg/mL of particle volume for both proteins in comparison with the UNOsphere S values of 170 ± 10 and 120 ± 10 mg/mL for lysozyme and IgG, respectively. Much higher adsorption rates were also found for Nuvia S, and the rate was nearly independent of protein concentration in solution. Confocal laser scanning microscopy showed very sharp intraparticle protein concentration profiles for UNOsphere S, consistent with a pore diffusion mechanism but diffuse concentration profiles for Nuvia S, consistent with a solid diffusion mechanism. The improved capacity and transport afforded by the polymeric extenders provide substantial potential benefits for bioprocess applications without sacrificing the desirable flow properties of the backbone matrix.     

Geometrical constraints in the scaling relationships between genome size, cell size and cell cycle length in herbaceous plants

Plant nuclear genome size (GS) varies over three orders of magnitude and is correlated with cell size and growth rate. We explore whether these relationships can be owing to geometrical scaling constraints. These would produce an isometric GS-cell volume relationship, with the GS-cell diameter relationship with the exponent of 1/3. In the GS-cell division relationship, duration of processes limited by membrane transport would scale at the 1/3 exponent, whereas those limited by metabolism would show no relationship. We tested these predictions by estimating scaling exponents from 11 published datasets on differentiated and meristematic cells in diploid herbaceous plants. We found scaling of GS-cell size to almost perfectly match the prediction. The scaling exponent of the relationship between GS and cell cycle duration did not match the prediction. However, this relationship consists of two components: (i) S phase duration, which depends on GS, and has the predicted 1/3 exponent, and (ii) a GS-independent threshold reflecting the duration of the G1 and G2 phases. The matches we found for the relationships between GS and both cell size and S phase duration are signatures of geometrical scaling. We propose that a similar approach can be used to examine GS effects at tissue and whole plant levels.     

The role of pi-acidic and pi-basic chiral stationary phases in the high-performance liquid chromatographic enantioseparation of unusual beta-amino acids

The application of 3,5-dimethylphenyl-carbamoylated-beta-cyclodextrin (Cyclobond I 2000 DMP) and 2,6-dinitro-4-trifluoromethylphenyl-ether-beta-cyclodextrin-based (Cyclobond DNP) chiral stationary phases for the high-performance liquid chromatographic enantioseparation of unusual beta-amino acids is reported. The investigated amino acids were saturated or unsaturated alicyclic beta-3-homo-amino acids and bicyclic beta-amino acids. Prior to chromatographic analyses, all amino acids were transformed to N-3,5-dinitrobenzoyl- or N-3,5-dimethylbenzoyl form to ensure a pi-acidic or pi-basic function and to enhance the pi-acidic-pi-basic interactions between analytes and chiral selectors. Chromatographic results are given as retention, separation and resolution factors. The chromatographic conditions were varied to achieve optimal separation. The sequence of elution of the enantiomers was determined in some cases.     

Dodging the moon: The moon effect on activity allocation of prey in the presence of predators

Animals can adapt their activity patterns throughout the circadian cycle. Prey may use moonlight as a predation risk cue and allocate their activity to lower risk periods. Here, we assessed moon transit influence on the activity allocation of nocturnal mammalian prey, in the presence of a predator (pumas, Puma concolor), during different moon phases, through camera trapping in Central Amazon. Thirty camera traps were installed 2 km apart from each other in each of our three study sites. Prey record distributions were assessed across the moon cycle, and their daily activity patterns were described in each moon phase. The record distributions of pacas (Cuniculus paca) (N = 262) and armadillos (Dasypus sp.) (N = 244) were concentrated in darker nights, contrasting with red brocket deer (Mazama americana) (N = 123) and pumas (N = 31), whose records were evenly distributed through the moon cycle. Yet, every prey was found to avoid the brighter times of the night regardless of the moon phase. These findings suggest prey can shift the temporal distribution of their activities under different moon phases when predators are present, perhaps in response to predation risk variations.     

Mating behaviour of the ‘cosmopolitan’ species Phyllognathopus viguieri (Copepoda: Harpacticoida) and its systematical significance

The mating behaviour was studied and recorded on video with individuals of four cultures of Phyllognathopus viguieri from different populations obtained from the interstitial water of a slow sand filter near the river Ruhr (Germany) (Ruhr population), from a compost heap in Bethesda (Maryland, USA) (Maryland population), from a rain gauge in Windsor Campbell farm (Jamaica) (Jamaica population), and a tree trunk with moss in a forest in the municipality of Rio de Janeiro (Brazil) (Brazil population). The mating behaviour was divided into the well‐known initial phase, copula phase and postcopulatory mate guarding phase. An additional phase prior to the initial phase serves to recognize the female, the recognition phase. The mating behaviour is identical in the males of the Jamaica and Brazil populations of P. viguieri. A postcopulatory mate guarding phase is not found in these two groups. Here, we refute the hypothesis, that a postcopulatory mate guarding phase is found in taxa in which only adult males grasp adult females. The males of the Ruhr and Maryland populations differ from each other in their mating behaviour. Generally, the males of all four populations do not mate with fertilized females which are equally unattractive to the males, i.e., females mate only once in their lifetime to produce offspring. These results corroborate the view that the different populations of P. viguieri do not belong to a single cosmopolitan species.