Dissipative electron-phonon system photoexcited far from equilibrium

We derive the steady-state electron distribution function for a semiconductor driven far from equilibrium by the inter-band photoexcitation assumed homogeneous over the nanoscale sample. Our analytical treatment is based on the generalization of a stochastic model known for a driven dissipative granular gas. The generalization is physically realizable in a semiconducting sample where electrons are injected into the conduction band by photoexcitation, and removed through the electron-hole recombination process at the bottom of the conduction band. Here the kinetics of the electron-electron and the electron-phonon (bath) scattering processes, as also the partitioning of the total energy in the inelastic collisions, are duly parametrized by certain rate constants. Our analytical results give the steady-state-energy distribution of the classical (non-degenerate) electron gas as function of the phonon (bath) temperature and the rates of injection (cw pump) and depletion (recombination). Interestingly, we obtain an accumulation of the electrons at the bottom of the conduction band in the form of a delta-function peak $-$ a non-equilibrium classical analogue of condensation. Our model is specially appropriate to a disordered, indirect band-gap, polar semiconducting sample where energy is the only state label, and the electron-phonon coupling is strong while the recombination rate is slow. A possible mechanism for the dissipative inelastic collisions between the electrons is also suggested.Comment: 4 page

Quantum diffusion on a dynamically disordered and harmonically driven lattice with static bias: decoherence

We revisit the problem of quantum diffusion of a particle moving on a lattice with dynamical disorder. Decoherence, essential for the diffusive motion, is introduced via a set of Lindblad operators, known to guarantee per se the positivity, Hermiticity and the trace-class nature of the reduced density matrix, are derived and solved analytically for several transport quantities of interest. For the special Hermitian choice of the Lindblad operators projected onto the lattice sites, we recover several known results, obtained by others, e.g. through the stochastic Liouville equation using phenomenological damping terms for the off-diagonal density-matrix elements. An interesting result that we obtained is for the case of a 1D lattice with static potential bias and a time-harmonic modulation (ac drive) of its transition-matrix element, where the diffusion coefficient shows an oscillatory behavior as function of the drive amplitude and frequency - clearly, a Wannier-Stark ladder signature. The question of dissipation is also briefly discussed

Molecular Strategies for Developing Salt Tolerant Crops

121-137Salinity is one of the most important abiotic stresses for agricultural crops. High concentrations of salts cause hyperosmotic and ionic stresses, which, in turn, may generate secondary stresses such as oxidative stress, etc. The complexity and polygenic nature of salt tolerance trait has seriously limited the efforts to develop salt-tolerant crop varieties. This paper reviews new molecular strategies that have been or can be used for the molecular dissection of plant responses to salt stress, discovery of novel structural and regulatory genes involved in stress adaptation, and transgenic and molecular marker strategies used for engineering salt tolerance in plants. Application of novel techniques such as genome sequencing, high-throughput analysis of genomic-scale expressed sequence tags (ESTs), DNA chips/cDNA microarray analyses, targeted or random mutagenesis, knockouts, molecular mapping and gain-of-function or mutant complementation, is expected to accelerate the discovery of the new genes involved in stress adaptation as well as improve understanding of stress biology. A number of stress-related genes have been characterized including the ones that encode for important enzymes or a biochemical pathway, participate in signaling pathways or act as transcriptional regulators for coordinated regulation of stress related genes. Some of these genes have been successfully transferred in model plant species including Arabidopsis, rice and tobacco, and a marginal to significant improvement in salt-tolerance has been reported. In addition, molecular markers can be used for linkage mapping of genes/QTLs for salinity tolerance trait, marker-assisted transfer and pyramiding of such QTLs into agronomically desirable genotypes and/or for map-based cloning of genes. Application of transgenic and molecular marker research coupled with rapid gene discovery via functional genomic research in plants shall provide effective means for designing salt-tolerant crops.</span

Molecular strategies for developing salt tolerant crops

Salinity is one of the most important abiotic stresses for agricultural crops. High concentrations of salts cause hyperosmotic and ionic stresses, which, in turn, may generate secondary stresses such as oxidative stress, etc. The complexity and polygenic nature of salt tolerance trait has seriously limited the efforts to develop salt-tolerant crop varieties. This paper reviews new molecular strategies that have been or can be used for the molecular dissection of plant responses to salt stress, discovery of novel structural and regulatory genes involved in stress adaptation, and transgenic and molecular marker strategies used for engineering salt tolerance in plants. Application of novel techniques such as genome sequencing, high-throughput analysis of genomic-scale expressed sequence tags (ESTs), DNA chips/cDNA microarray analyses, targeted or random mutagenesis, knockouts, molecular mapping and gain-of-function or mutant complementation, is expected to accelerate the discovery of the new genes involved in stress adaptation as well as improve understanding of stress biology. A number of stress-related genes have been characterized including the ones that encode for important enzymes or a biochemical pathway, participate in signaling pathways or act as transcriptional regulators for coordinated regulation of stress related genes. Some of these genes have been successfully transferred in model plant species including Arabidopsis, rice and tobacco, and a marginal to significant improvement in salt-tolerance has been reported. In addition, molecular markers can be used for linkage mapping of genes/QTLs for salinity tolerance trait, marker-assisted transfer and pyramiding of such QTLs into agronomically desirable genotypes and/or for map-based cloning of genes. Application of transgenic and molecular marker research coupled with rapid gene discovery via functional genomic research in plants shall provide effective means for designing salt-tolerant crops

The GET pathway is a major bottleneck for maintaining proteostasis in Saccharomyces cerevisiae

Abstract A hallmark of aging in a variety of organisms is a breakdown of proteostasis and an ensuing accumulation of protein aggregates and inclusions. However, it is not clear if the proteostasis network suffers from a uniform breakdown during aging or if some distinct components act as bottlenecks especially sensitive to functional decline. Here, we report on a genome-wide, unbiased, screen for single genes in young cells of budding yeast required to keep the proteome aggregate-free under non-stress conditions as a means to identify potential proteostasis bottlenecks. We found that the GET pathway, required for the insertion of tail-anchored (TA) membrane proteins in the endoplasmic reticulum, is such a bottleneck as single mutations in either GET3, GET2 or GET1 caused accumulation of cytosolic Hsp104- and mitochondria-associated aggregates in nearly all cells when growing at 30 °C (non-stress condition). Further, results generated by a second screen identifying proteins aggregating in GET mutants and analyzing the behavior of cytosolic reporters of misfolding, suggest that there is a general collapse in proteostasis in GET mutants that affects other proteins than TA proteins

Calcineurin stimulation by Cnb1p overproduction mitigates protein aggregation and α-synuclein toxicity in a yeast model of synucleinopathy

Abstract The calcium-responsive phosphatase, calcineurin, senses changes in Ca2+ concentrations in a calmodulin-dependent manner. Here we report that under non-stress conditions, inactivation of calcineurin signaling or deleting the calcineurin-dependent transcription factor CRZ1 triggered the formation of chaperone Hsp100p (Hsp104p)-associated protein aggregates in Saccharomyces cerevisiae. Furthermore, calcineurin inactivation aggravated α-Synuclein-related cytotoxicity. Conversely, elevated production of the calcineurin activator, Cnb1p, suppressed protein aggregation and cytotoxicity associated with the familial Parkinson’s disease-related mutant α-Synuclein A53T in a partly CRZ1-dependent manner. Activation of calcineurin boosted normal localization of both wild type and mutant α-synuclein to the plasma membrane, an intervention previously shown to mitigate α-synuclein toxicity in Parkinson’s disease models. The findings demonstrate that calcineurin signaling, and Ca2+ influx to the vacuole, limit protein quality control in non-stressed cells and may have implications for elucidating to which extent aberrant calcineurin signaling contributes to the progression of Parkinson’s disease(s) and other synucleinopathies. Video Abstrac

Hsp90-Associated Immunophilin Homolog Cpr7 Is Required for the Mitotic Stability of [URE3] Prion in <i>Saccharomyces cerevisiae</i>

<div><p>The role of Hsp70 chaperones in yeast prion propagation is well established. Highly conserved Hsp90 chaperones participate in a number of cellular processes, such as client protein maturation, protein degradation, cellular signalling and apoptosis, but little is known about their role in propagation of infectious prion like aggregates. Here, we examine the influence of Hsp90 in the maintenance of yeast prion [URE3] which is a prion form of native protein Ure2, and reveal a previously unknown role of Hsp90 as an important regulator of [URE3] stability. We show that the C-terminal MEEVD pentapeptide motif, but not the client maturation activity of Hsp90, is essential for [URE3] prion stability. In testing deletions of various Hsp90 co-chaperones known to bind this motif, we find the immunophilin homolog Cpr7 is essential for [URE3] propagation. We show that Cpr7 interacts with Ure2 and enhances its fibrillation. The requirement of Cpr7 is specific for [URE3] as its deletion does not antagonize both strong and weak variant of another yeast prion [<i>PSI</i>^<i>+</i>], suggesting a distinct role of the Hsp90 co-chaperone with different yeast prions. Our data show that, similar to the Hsp70 family, the Hsp90 chaperones also influence yeast prion maintenance, and that immunophilins could regulate protein multimerization independently of their activity as peptidyl-prolyl isomerases.</p></div

The loss of [URE3] upon Cpr7 deletion is not due to altered expression of other major chaperones.

<p>(A) Yeast lysates from wild type (wt) [URE3], wild type [ure-o] and <i>cpr7Δ</i> strains were probed with antibodies against Ydj1, Sse1 and Hsp90. The chaperones were found to be expressed at similar levels in the strains examined. Loading control is same blot stained with amido-black. (B) 5μg (1X) or 10μg (2X) of total lysate protein was loaded into each lane and probed with anti Hsp70 antibodies. As seen, increased Hsp70 level was observed in strain lacking Cpr7 as compared to wt [URE3] or wt [ure-o] strains. (C) SY187(wt) expressing additional Ssa Hsp70 from transformed plasmids pRS315P_SSA2-SSA1/SSA2/SSA3/SSA4 or pRS315 empty vector were spread onto leucine deficient SD solid medium with limiting adenine. As seen by white colony color phenotype of transformants, the increased expression of Ssa Hsp70 supports stable [URE3].</p

Genomic and Functional Characterization of a Novel Burkholderia sp. Strain AU4i from Pea Rhizosphere Conferring Plant Growth Promoting Activities

Members of Burkholderia genus are gaining importance for their application in crop improvement by acting as plant growth-promoting rhizobacteria (PGPR), however, our knowledge about mechanisms of their plant growth promotion is limited. Herein, we aimed to isolate Burkholderia sp. from pea rhizosphere that confers plant growth promoting traits both in vitro and in vivo using pea seedlings as model. We have isolated a novel Burkholderia strain AU4i (B-AU4i) from pea rhizosphere that strongly promotes root and shoot growth in plantae. B-AU4i confers phosphate solubilization, indole-3-acetic acid production, N2 fixation, ammonia production, siderophore production, HCN production, and inhibits growth of pathogenic fungi both in vitro and in vivo experiments where we employed pea-seedlings as model system. Sequencing of B-AU4i genome using the Illumina-HiSeq 1000 technology reveals that it contains genes for the above-mentioned biofertilizer and biocontrol activities. The findings demonstrate the potential use of B-AU4i as plant growth promoter, which could be due to the presence of relevant genes in its genome. The current study improves our knowledge regarding the genes present in Burkholderia spp. that are involved in its plant growth promotion activities. B-AU4i strain can be used for improving agriculture productivity owing to its strong biofertilizer and biocontrol activity.Fil: Usha, Devi. Shoolini University; IndiaFil: Khatri, Indu. Council of Scientific & Industrial Research. Institute of Microbial Technology; IndiaFil: Lalit, Kumar. Shoolini University; IndiaFil: Devender, Singh. Shoolini University; IndiaFil: Aditi, Gupta. Shoolini University; IndiaFil: Navinder, Kumar. Council of Scientific & Industrial Research. Institute of Microbial Technology; IndiaFil: Gárriz, Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); ArgentinaFil: Subramanian, Srikrishna. Council of Scientific & Industrial Research. Institute of Microbial Technology; IndiaFil: Sharma, Deepak. Council of Scientific & Industrial Research. Institute of Microbial Technology; IndiaFil: Adesh, Saini K.. Shoolini University; Indi