Molecular dynamics simulation of film size and vacancy defect effects on the thermal conductivities of argon thin films

It is well known that there is a size effect for the thermal conductivity of thin films and that vacancy defects in film reduce the film's thermal conduction. In this paper, the film size and vacancy defect effects on the thermal conductivities of argon thin films were studied by molecular dynamics simulations. The results show the existence of phonon boundary scattering. The results also confirm that the theoretical model based on the Boltzmann equation can accurately model the thermal conduction of thin argon films. Both the theoretical and MD results illustrate that, although, both the defect and the thickness of the thin film deduce the thermal conductivity, their physical mechanisms differ.     

Plant regeneration and genetic transformation of C. canadensis: a non-model plant appropriate for investigation of flower development in Cornus (Cornaceae)

Key message

Efficient Agrobacterium -mediated genetic transformation for investigation of genetic and molecular mechanisms involved in inflorescence architectures in Cornus species.

Abstract

Cornus canadensis is a subshrub species in Cornus, Cornaceae. It has recently become a favored non-model plant species to study genes involved in development and evolution of inflorescence architectures in Cornaceae. Here, we report an effective protocol of plant regeneration and genetic transformation of C. canadensis. We use young inflorescence buds as explants to efficiently induce calli and multiple adventitious shoots on an optimized induction medium consisting of basal MS medium supplemented with 1 mg/l of 6-benzylaminopurine and 0.1 mg/l of 1-naphthaleneacetic acid. On the same medium, primary adventitious shoots can produce a large number of secondary adventitious shoots. Using leaves of 8-week-old secondary shoots as explants, GFP as a reporter gene controlled by 35S promoter and hygromycin B as the selection antibiotic, a standard procedure including pre-culture of explants, infection, co-cultivation, resting and selection has been developed to transform C. canadensis via Agrobacterium strain EHA105-mediated transformation. Under a strict selection condition using 14 mg/l hygromycin B, approximately 5 % explants infected by Agrobacterium produce resistant calli, from which clusters of adventitious shoots are induced. On an optimized rooting medium consisting of basal MS medium supplemented with 0.1 mg/l of indole-3-butyric acid and 7 mg/l hygromycin B, most of the resistant shoots develop adventitious roots to form complete transgenic plantlets, which can grow normally in soil. RT-PCR analysis demonstrates the expression of GFP transgene. Green fluorescence emitted by GFP is observed in transgenic calli, roots and cells of transgenic leaves under both stereo fluorescence microscope and confocal microscope. The success of genetic transformation provides an appropriate platform to investigate the molecular mechanisms by which the various inflorescence forms are developed in Cornus plants.     

Variation in cadmium accumulation and translocation among peanut cultivars as affected by iron deficiency

Purpose

The current study aimed to test the hypothesis that the variations in shoot Cd accumulation among peanut cultivars was ascribed to the difference in capacity of competition with Fe transport, xylem loading and transpiration.

Methods

A hydroponics experiment was conducted to determine the plant biomass, gas exchange, and Cd accumulation in Fe-sufficient or -deficient plants of 12 peanut cultivars, at low Cd level (0.2 μM CdCl₂).

Results

Peanut varied among cultivars in morpho-physiological response to Cd stress as well as Cd accumulation, translocation and distribution. Qishan 208 and Xvhua 13 showed a higher capacity for accumulating Cd in their shoots. Fe deficiency increased the concentration and amount of Cd in plant organs, but decreased TF _{root to shoot} and TF _{root to stem}, while TF _{stem to leaf} remained unaffected. Fe deficiency-induced increase rates of Cd concentration and total Cd amount in roots and leaves were negatively correlated with the values in Fe-sufficient plants. Transpiration rate was positively correlated with leaf Cd concentration, TF _{root to shoot}, TF _{root to stem} and TF _{stem to leaf}.

Conclusions

The difference in shoot Cd concentration among peanut cultivars was mainly ascribed to the difference in Fe transport system, xylem loading capacity and transpiration.     

Detection of Proton Movement Directly across Viral Membranes To Identify Novel Influenza Virus M2 Inhibitors

The influenza virus M2 protein is a well-validated yet underexploited proton-selective ion channel essential for influenza virus infectivity. Because M2 is a toxic viral ion channel, existing M2 inhibitors have been discovered through live virus inhibition or medicinal chemistry rather than M2-targeted high-throughput screening (HTS), and direct measurement of its activity has been limited to live cells or reconstituted lipid bilayers. Here, we describe a cell-free ion channel assay in which M2 ion channels are incorporated into virus-like particles (VLPs) and proton conductance is measured directly across the viral lipid bilayer, detecting changes in membrane potential, ion permeability, and ion channel function. Using this approach in high-throughput screening of over 100,000 compounds, we identified 19 M2-specific inhibitors, including two novel chemical scaffolds that inhibit both M2 function and influenza virus infectivity. Counterscreening for nonspecific disruption of viral bilayer ion permeability also identified a broad-spectrum antiviral compound that acts by disrupting the integrity of the viral membrane. In addition to its application to M2 and potentially other ion channels, this technology enables direct measurement of the electrochemical and biophysical characteristics of viral membranes.     

The Highly Conserved Layer-3 Component of the HIV-1 gp120 Inner Domain Is Critical for CD4-Required Conformational Transitions

The trimeric envelope glycoprotein (Env) of human immunodeficiency virus type 1 (HIV-1) mediates virus entry into host cells. CD4 engagement with the gp120 exterior envelope glycoprotein subunit represents the first step during HIV-1 entry. CD4-induced conformational changes in the gp120 inner domain involve three potentially flexible topological layers (layers 1, 2, and 3). Structural rearrangements between layer 1 and layer 2 have been shown to facilitate the transition of the envelope glycoprotein trimer from the unliganded to the CD4-bound state and to stabilize gp120-CD4 interaction. However, our understanding of CD4-induced conformational changes in the gp120 inner domain remains incomplete. Here, we report that a highly conserved element of the gp120 inner domain, layer 3, plays a pivot-like role in these allosteric changes. In the unliganded state, layer 3 modulates the association of gp120 with the Env trimer, probably by influencing the relationship of the gp120 inner and outer domains. Importantly, layer 3 governs the efficiency of the initial gp120 interaction with CD4, a function that can also be fulfilled by filling the Phe43 cavity. This work defines the functional importance of layer 3 and completes a picture detailing the role of the gp120 inner domain in CD4-induced conformational transitions in the HIV-1 Env trimer.     

Malleola tibetica sp. nov. (Aeridinae,Orchidaceae) from Tibet,China

Malleola tibetica, a new species from southeastern tropical Tibet, China, is described and illustrated. Morphologically, the new species is closely related to M. dentifera, but differs from it by having uniformly green leaves, flowers with entire lateral lobes of the lip and a basally thickened mid‐lobe, and a column that is densely cristaline‐papillose adaxially.     

Screening proteins interacting with VpPR10.1 of Chinese wild grapevine using the yeast two-hybrid system

Among the 17 plant pathogenesis-related (PR) protein families, only PR10 family is intracellular and cytosolic. PR proteins are expressed in response to pathogen challenge and abiotic stresses in higher plants. However, the molecular mechanisms of their actions remain poorly understood. In a previous work, we isolated a PR10 gene from Erysiphe necator-resistant Chinese wild Vitis sp. (Baihe-35-1) and it was designated as VpPR10.1. In this study, yeast two-hybrid method was used to screen proteins interacting with VpPR10.1 proteins. Twenty-one ESTs were isolated and sequenced. All sequences were compared using BLASTx to identify presumptive orthologs. Several proteins associated with VpPR10.1 protein were screened, including CNR8, UFGT6, HSP, DEAD-box, Trx h2, Grx C9 and GLOX. These proteins are closely related to defensive action of plants against pathogens and abiotic stresses. Our results reveal that VpPR10.1 gene may be involved in hormone signaling, programmed cell death and defense responses of grapevine.