Herbivore exposure alters ion fluxes and improves salt tolerance in a desert shrub

Plants have evolved complex mechanisms that allow them to withstand multiple environmental stresses, including biotic and abiotic stresses. Here, we investigated the interaction between herbivore exposure and salt stress of Ammopiptanthus nanus, a desert shrub. We found that jasmonic acid (JA) was involved in plant responses to both herbivore attack and salt stress, leading to an increased NaCl stress tolerance for herbivore-pretreated plants and increase in K⁺/Na⁺ ratio in roots. Further evidence revealed the mechanism by which herbivore improved plant NaCl tolerance. Herbivore pretreatment reduced K⁺ efflux and increased Na⁺ efflux in plants subjected to long-term, short-term, or transient NaCl stress. Moreover, herbivore pretreatment promoted H⁺ efflux by increasing plasma membrane H⁺-adenosine triphosphate (ATP)ase activity. This H⁺ efflux creates a transmembrane proton motive force that drives the Na⁺/H⁺ antiporter to expel excess Na⁺ into the external medium. In addition, high cytosolic Ca²⁺ was observed in the roots of herbivore-treated plants exposed to NaCl, and this effect may be regulated by H⁺-ATPase. Taken together, herbivore exposure enhance s A. nanus tolerance to salt stress by activating the JA-signalling pathway, increasing plasma membrane H ⁺ - ATPase activity, promoting cytosolic Ca²⁺ accumulation, and then restricting K⁺ leakage and reducing Na⁺ accumulation in the cytosol.     

The effect of compatible solutes on proteins

Summary The ability of the compatible solute, proline, to affect the behavior of proteins has been examined in many different systems by many researches. In the present study of protein solvation, proline has been shown to prevent or diminish, in a concentration-dependent manner, the glutamine synthetase-precipitating ability of polyethylene glycol (PEG). The effects of PEG concentration and molecular weight are reduced by proline, and the interaction is strongly affected by pH.PEG causes precipitation of many proteins, and the ability of proline to reduce the precipitation of two non-enzymatic conjugated proteins, alfalfa mosaic virus and an³H-testosterone/antiserum complex, was also examined. Proline was effective in reducing the PEG-induced precipitation of both proteins. Virus precipitation by PEG and its alleviation by proline are influenced by pH. The increased virus-precipitating effect of PEG in the presence of salt (NaCl) is also alleviated by proline. The precipitation of the radioimmune complex by PEG is diminished by proline and by a mixture of free amino acids.These results indicate the generality of the three-way interaction between proline, protein and PEG. They may be of importance for extraction of proteins from biological systems and in studies of enzyme inactivation or protein denaturation in a cytoplasmic milieu. The results suggest that the protective effects of some amino acids are at least additive and are consistent with the conclusion that the compatible solutes protect protein-containing systems against the unfavorable consequences of dehydration and other stresses, by increasing the tendency of the system to maintain thestatus quo.     

Biosynthesis and regulation of superoxide dismutases

The past two decades have witnessed an explosion in our understanding of oxygen toxicity. The discovery of superoxide dismutases (SODs) (EC.1.15.1.1), which specifically catalyze the dismutation of superoxide radicals (O₂⁻) to hydrogen peroxide (H₂O₂) and oxygen, has indicated that O₂⁻ is a normal and common byproduct of oxygen metabolism. There is an increasing evidence to support the conclusion that superoxide radicals play a major role in cellular injury, mutagenesis, and many diseases. In all cases SODs have been shown to protect the cells against these deleterious effects. Recent advances in molecular biology and the isolation of different SOD genes and SOD c-DNAs have been useful in proving beyond doubt the physiological function of the enzyme. The biosynthesis of SODs, in most biological systems, is under rigorous controls. In general, exposure to increased pO₂, increased intracellular fluxes of O₂⁻, metal ions perturbation, and exposures to several environmental oxidants have been shown to influence the rate of SOD synthesis in both prokaryotic and eukaryotic organisms. Recent developments in the mechanism of regulation of the manganese-containing superoxide dismutase of Escherichia coli will certainly open new research avenues to better understand the regulation of SODs in other organisms.     

Binucleation to breed new plant species adaptable to their environments

Classical plant breeding approaches may fall short to breed new plant species of high environmental and ecological interests. Biotechnological and genetic manipulations, on the other hand, may hold more effective capabilities to circumvent the limitations of sexual incompatibility and conventional breeding programs. Given that plant cells encompass multiple copies of organellar genomes (mitochondrial and plastidial genomes), an important question could be raised about whether an artificial attempt to duplicate the nuclear genome might also be conceivable through a binucleation approach (generating plant cells with 2 nuclei from 2 different plant species) for potential production of new polyploidies that would characterize new plant species. Since the complexities of plant genomes are the result of multiple genome duplications, an artificial binucleation approach would thus be of some interest to eventually varying plant genomes and producing new polyploidy from related or distal plant species. Here, I discuss the potentiality of such an approach to engineer binucleated plant cells as a germ of new plant species to fulfill some environmental applications such as increasing the biodiversity and breeding new species adaptable to harsh environmental stresses and increasing green surfaces to reduce atmospheric pollutions in arid lands with poor vegetation.     

Nanoindentation as a Probe of Nanoscale Residual Stresses: Atomistic Simulation Results

Abstract

Results from two sets of molecular dynamics simulations are reported. In the first set of simulations a nanoscale tip was used to indent single-crystal gold lattices subjected to external strains. These were carried out to explore possible relationships between nanoindentation curves and elastic properties of uniformly strained films. The changes in the slope of the loading curves reflect the stress state of the sample. In the second set of simulations the use of shallow nanoindentation for mapping nonuniform residual surface stress near a dislocation intersecting a surface was tested. Correlation between the maximum force on the tip and the initial local stresses at the point of indentation were observed. Preliminary atomistic simulations indicate that atomic-force microscopy can be used as a nondestructive, nanoscale probe of the surface stress distributions.     

盐度胁迫对鲻鱼幼鱼鳃丝Na+/K+-ATP酶活力 和体含水量的影响

研究了环境盐度急性胁迫对鲻鱼幼鱼(Mugil cephalus)鳃丝Na+/K+-ATPase(NKA)活性及体内含水量的影响.结果表明,将幼鱼从S33(盐度33)的对照组中直接转移至S0(盐度0)、S10(盐度10)、S20(盐度20)、S33和S40(盐度40)的水体中,随盐度降低各盐度处理的死亡率迅速升高.各处理...     

非生物胁迫下植物脱水素的研究进展

脱水素是LEA蛋白中的一类,广泛存在于植物的各个组织器官及植物胚胎发育后期.脱水素是植物在受低温、干旱和高盐等非生物逆境胁迫时合成的一类高亲水性保护蛋白,具有保护核酸、胞内蛋白和膜结构免受损害的功能.许多研究已经证实在非生物胁迫下,植物脱水素的表达与积累和植物抗逆性之间存在着紧密的联系.对脱水素的结构、亚细胞定位、基因表达模式及非生物胁迫下脱水素作用的最新研究成果进行了综述.     

The impact of fluid-dynamic-generated stresses on chDNA and pDNA stability during alkaline cell lysis for gene therapy products.

Extensive tests have been carried out to assess the impact of fluid-dynamic-generated stress during alkaline lysis of Escherichia coli cells (host strain DH1 containing the plasmid pTX 0161) to produce a plasmid DNA (pDNA) solution for gene therapy. Both a concentric cylinder rheometer and two stirred reactors have been used, and both the alkaline addition and neutralization stages of lysis have been studied. Using a range of shear rates in the rheometer, stirrer speeds in the reactors, and different periods of exposure, their impact on chromosomal DNA (chDNA) and pDNA was assessed using agarose gel electrophoresis, a Qiagen Maxiprep with a polymerase chain reaction (PCR) assay, and a Qiagen Miniprep purification with a UV spectrophotometer. Comparison has been made with unstressed material subjected to similar holding times. These tests essentially show that under all these conditions, <2% chDNA was present in the pDNA solution, the pDNA itself was not fragmented, and a yield of 1 mg/g cell was obtained. These results, together with studies of rheological properties, have led to the design of a 60-L, stirred lysis reactor and the production of high-quality pDNA solution with <1% chDNA after further purification.