Potential of efficient and resistant plant growth‐promoting rhizobacteria in lead uptake and plant defence stimulation in Lathyrus sativus under lead stress

• The ability of plant growth‐promoting rhizobacteria (PGPR) to enhance Lathyrus sativus tolerance to lead (Pb) stress was investigated.
• Ten consortia formed by mixing four efficient and Pb‐resistant PGPR strains were assessed for their beneficial effect in improving Pb (0.5 mM) uptake and in inducing the host defence system of L. sativus under hydroponic conditions based on various physiological and biochemical parameters.
• Lead stress significantly decreased shoot (SDW) and root (RDW) dry weight, but PGPR inoculation improved both dry weights, with highest increases in SDW and RDW of plants inoculated with I5 (R. leguminosarum (M5) + P. fluorescens (K23) + Luteibacter sp. + Variovorax sp.) and I9 (R. leguminosarum (M5) + Variovorax sp. + Luteibacter sp. + S. meliloti) by 151% and 94%, respectively. Additionally, inoculation significantly enhanced both chlorophyll and soluble sugar content, mainly in I5 inoculated leaves by 238% and 71%, respectively, despite the fact that Pb decreased these parameters. We also found that PGPR inoculation helps to reduce oxidative damage and enhances antioxidant enzyme activity, phenolic compound biosynthesis, carotenoids and proline content. PGPR inoculation increased Pb uptake in L. sativus, with highest increase in shoots of plants inoculated with I5 and I7, and in roots and nodules of plants inoculated with I1. Moreover, PGPR inoculation enhanced mineral homeostasis for Ca, Cu and Zn under Pb stress, mainly in plants inoculated with I1, I5, I7 and I9.
• Results of our study suggest the potential of efficient and Pb‐resistant PGPR in alleviating harmful effects of metal stress via activation of various defence mechanisms and enhancing Pb uptake that promotes tolerance of L. sativus to Pb stress.

     

Genetic structure and functioning of alien ship rat populations from a Corsican micro-insular complex

The detrimental effects of the introduced ship rat on bird species on the Lavezzi Mediterranean archipelago has led to the decision to eradicate the rodent from the main island, Lavezzu (73 ha), as well as from several neighbouring islets. A genetic study using eight microsatellite markers has revealed some of the dynamics of this rat population. First, it has been shown that the rat population was genetically stable (no departure from Hardy-Weinberg equilibrium and no linkage disequilibrium) and as suggested by paleontological data, established for a long time. This information is encouraging in term of viability of the eradication campaign in the long term, even if rare immigration events cannot be excluded. Second, this study shows that rats are likely to swim between the main island and the islets quite regularly since no clear genetic differentiation has been detected between them. This result is quite surprising since the ship rat is not known for its swimming abilities. Third, a cryptic genetic structure has been detected on the main island, with the north peninsula differentiated from the rest. This result correlates the observation of particular predation behaviours only observed in this part of the island. Finally, evolutionary hypotheses (e.g., dispersal limitation, emergence of family groups, local adaptation) are discussed to explain the genetic patterns observed and the population functioning inferred. These results should be of particular interest to wildlife managers concerned with rat eradications, and also provide clear insights into the study of other biological invasions.     

Binding of 2CA1P (nocturnal inhibitor) to the active site of RubisCO using Genetic Algorithm (GA)

Ribulose-1, 5- Bisphosphate carboxylase/ oxygenase (RubisCO) catalyzes the first step in net photosynthetic assimilation and photorespiratory carbon oxidation. The activity of this enzyme is modulated in response to changes in light intensity as suggested in a number of early reports. Several studies found that the natural inhibitor 2CA1P is involved in the inhibition of the enzyme under reduced light intensity in rice (Oryza sativa). Due to the lack of studies and information on the interaction between this inhibitor and the active site of the enzyme, we attempted to predict the interaction between the amino acids in the active site and the inhibitor using both Hyperchem7.5 and GOLD software. After the docking; three possibilities having the highest fitness score were found (65.71, 64.72, 62.04), in these possibilities the inhibitor was bound to the enzyme, the phosphate and carboxylate groups in the same positions with a clear difference in the position of OH. In order to confirm the accuracy of the genetic algorithm, the artificial inhibitor 2CABP was docked back in the active site of the enzyme using the same parameters used in the case of the 2CA1P and the algorithm''s predictions were compared with the experimentally observed binding mode. The results showed that the difference in the active sites before and after the docking was in the range of 0.93 Å which indicated that the results were very accurate. Depending on this result it was concluded that the results obtained in the case of the 2CA1P were close to the experimental results.     

Spurious localizations of diX-indigo microcrystals generated by the histochemical GUS assay

For several models expressing theuidA orgus reporter gene with or without a presequence for mitochondrial targeting, we have demonstrated that the compartmentation of -glucuronidase (E.C. 3.2.1.31) activity was not in agreement within situ localization of the diX-indigo microcrystals generated by the cytoenzymological GUS assay. These crystals were generally associated with the various cytomembranes and lipid inclusions. Experiments with purified -glucuronidase or withgus-expressing bacteria incubated with 5-bromo-4-chloro-3-indolyl--d-glucuronide and maize oil-phosphate buffer emulsion indicated that the intermediate products resulting from the GUS assay actively diffused and crystallized preferentially in association with lipids, sometimes far from the site of enzyme activity. This phenomenon could not be suppressed by the addition of potassium ferricyanide in the incubation medium. These findings are discussed with regard to previously reported biochemical and histochemical data on animal tissues, and focus on the necessity for caution in studies of tissue-specific gene expression using the GUS assay, particularly for lipid-rich plant models.     

Tobacco BY-2 cells expressing fission yeast cdc25 bypass a G2/M block on the cell cycle

The mitotic inducer gene from Schizosaccharomyces pombe, Spcdc25, was used as a tool to investigate regulation of G2/M in higher plants using the BY-2 (Nicotiana tabacum) cell line as a model. Spcdc25-expressing BY-2 cells exhibited a reduced mitotic cell size through a shortening of the G2 phase. The cells often formed isodiametric double files both in BY-2 cells and in cell suspensions derived from 35S::Spcdc25 tobacco plants. In Spcdc25-expressing cells, the tobacco cyclin-dependent kinase, NtCDKB1, showed high activity in early S phase, S/G2 and early M phase, whereas in empty vector cells CDKB1 activity was transiently high in early S phase but thereafter remained lower. Spcdc25-expressing cells also bypassed a block on G2/M imposed by the cytokinin biosynthetic inhibitor lovastatin (LVS). Surprisingly, cytokinins were at remarkably low levels in Spcdc25-expressing cells compared with the empty vector, explaining why these cells retained mitotic competence despite the presence of LVS. In conclusion, synchronised Spcdc25-expressing BY-2 cells divided prematurely at a small cell size, and they exhibited premature, but sustained, CDKB1 activity even though endogenous cytokinins were virtually undetectable.     

Screening Approach for Chiral Separation of β‐Aminoketones by HPLC on Various Polysaccharide‐Based Chiral Stationary Phases

Nine β‐aminoketones were synthesized via Mannich reaction when benzaldehyde was condensed with some primary amines and acetophenone. The purified compounds were identified by using spectroscopic methods. The enantiomeric separation of these derivatives was carried out by high‐performance liquid chromatography (HPLC) using several coated and immobilized polysaccharide stationary phases, namely, Chiralcel^® OD‐H, Chiralcel^® OD, Chiralcel^® OJ, Chiralpak^® AD, Chiralpak^® IA, and Chiralpak^® IB using different mobile phases composed of n‐hexane and alcohol mixed in various ratios or pure ethanol or isopropanol. The retention behavior and selectivity of these chiral stationary phases were examined in isocratic normal phase mode. The results indicate that cellulose derivatives have higher enantioselectivity than amylose derivatives for the separation of racemic β‐amino ketones. Chirality 27:332–338, 2015. © 2015 Wiley Periodicals, Inc.     

Single Mechanosensitive and Ca2+-Sensitive Channel Currents Recorded from Mouse and Human Embryonic Stem Cells

Cell-attached and inside-out patch clamp recording was used to compare the functional expression of membrane ion channels in mouse and human embryonic stem cells (ESCs). Both ESCs express mechanosensitive Ca²⁺ permeant cation channels (MscCa) and large conductance (200 pS) Ca²⁺-sensitive K⁺ (BK_Ca2+) channels but with markedly different patch densities. MscCa is expressed at higher density in mESCs compared with hESCs (70 % vs. 3 % of patches), whereas the BK_Ca2+ channel is more highly expressed in hESCs compared with mESCs (~50 % vs. 1 % of patches). ESCs of both species express a smaller conductance (25 pS) nonselective cation channel that is activated upon inside-out patch formation but is neither mechanosensitive nor strictly Ca²⁺-dependent. The finding that mouse and human ESCs express different channels that sense membrane tension and intracellular [Ca²⁺] may contribute to their different patterns of growth and differentiation in response to mechanical and chemical cues.