ALBERT

Description: Genesis of porphyry Cu deposits remains controversial. A common view suggests that the efficient partitioning of Cu into a fluid exsolved from a calc-alkaline magma with normal Cu but elevated S concentrations is critical to ore formation. However, this view was recently challenged by two new ideas, which emphasize that the formation of porphyry Cu deposits requires anomalously Cu rich sources of either a mantle domain or intracrustal magmatic cumulate. Here we report data on an intracrustal magmatic hornblendite, genetically associated with the large Mujicun porphyry Cu deposit in North China craton. Petrographic observations, geochemical data, and P-T calculations indicate that the hornblendite formed at a depth of ~28 km by amphibole accumulation from a basaltic magma. These cumulates, despite containing traces of Cu-bearing sulfides, have Cu contents of only 17 to 60 ppm, close to primitive arc magmas. Their parental magma, initially not Cu enriched, evolved to ≥60 ppm Cu in resultant gabbronorite emplaced at ca. 8 km. This was followed by strong Cu depletion (〈10 ppm) in the quartz-diorite porphyries associated with Cu mineralization. Most of the gabbronorites contain magmatic sulfide phases that have been partially dissolved by hydrothermal fluids. One sample contains sulfide droplets and coexisting silicate glass and fluid inclusions that were locally trapped in interstitial magmatic quartz. We conclude that the exsolution of a Cu-rich sulfide melt and its subsequent redissolution into aqueous fluids was a significant factor in the formation of the Mujicun porphyry Cu deposit, and that anomalous Cu enrichments in the mantle source regime or intracrustal cumulates were not required to form the ore deposit.

Description: Virus-induced gene silencing (VIGS) has been shown to be an effective tool for investigating gene functions in herbaceous plant species, but has rarely been tested in trees. The establishment of a fast and reliable transformation system is especially important for woody plants, many of which are recalcitrant to transformation. In this study, we established a tobacco rattle virus (TRV)-based VIGS system for two Populus species, Populus euphratica and P.   x   canescens . Here, TRV constructs carrying a 266 bp or a 558 bp fragment of the phytoene desaturase (PDS) gene were Agrobacterium -infiltrated into leaves of the two poplar species. Agrobacterium -mediated delivery of the shorter insert, TRV2 -PePDS 266 , into the host poplars resulted in expected photobleaching in both tree species, but not the longer insert, PePDS 558 . The efficiency of VIGS was temperature-dependent, increasing by raising the temperature from 18 to 28 °C. The optimized TRV–VIGS system at 28 °C resulted in a high silencing frequency and efficiency up to 65–73 and 83–94%, respectively, in the two tested poplars. Moreover, syringe inoculation of Agrobacterium in 100 mM acetosyringone induced a more efficient silencing in the two poplar species, compared with other agroinfiltration methods, e.g., direct injection, misting and agrodrench. There were plant species-related differences in the response to VIGS because the photobleaching symptoms were more severe in P.   x   canescens than in P. euphratica. Furthermore, VIGS-treated P. euphratica exhibited a higher recovery rate (50%) after several weeks of the virus infection, compared with TRV-infected P.   x   canescens plants (20%). Expression stability of reference genes was screened to assess the relative abundance of PePDS mRNA in VIGS-treated P. euphratica and P.   x   canescens. PeACT7 was stably expressed in P. euphratica and UBQ-L was selected as the most suitable reference gene for P.   x   canescens using three different statistical approaches, geNorm, NormFinder and BestKeeper. Quantitative real-time PCR showed significant reductions in PDS transcripts (55–64%) in the photobleached leaves of both VIGS-treated poplar species. Our results demonstrate that the TRV-based VIGS provides a practical tool for gene functional analysis in Populus sp., especially in those poplar species which are otherwise recalcitrant to transformation.

Description: Insect-induced defenses occur in nearly all plants and are regulated by conserved signaling pathways. As the first described plant peptide signal, systemin regulates antiherbivore defenses in the Solanaceae, but in other plant families, peptides with analogous activity have remained elusive. In the current study, we demonstrate that a member of...

Description: Growth arrest and DNA-damage-inducible protein 45 (Gadd45) family members have been implicated in DNA demethylation in vertebrates. However, it remained unclear how they contribute to the demethylation process. Here, we demonstrate that Gadd45a promotes active DNA demethylation through thymine DNA glycosylase (TDG) which has recently been shown to excise 5-formylcytosine (5fC) and 5-carboxylcytosine (5caC) generated in Ten-eleven-translocation (Tet)—initiated oxidative demethylation. The connection of Gadd45a with oxidative demethylation is evidenced by the enhanced activation of a methylated reporter gene in HEK293T cells expressing Gadd45a in combination with catalytically active TDG and Tet. Gadd45a interacts with TDG physically and increases the removal of 5fC and 5caC from genomic and transfected plasmid DNA by TDG. Knockout of both Gadd45a and Gadd45b from mouse ES cells leads to hypermethylation of specific genomic loci most of which are also targets of TDG and show 5fC enrichment in TDG-deficient cells. These observations indicate that the demethylation effect of Gadd45a is mediated by TDG activity. This finding thus unites Gadd45a with the recently defined Tet-initiated demethylation pathway.

Description: The Northeastern China involves complex interactions between the East Asian summer monsoon (EASM) circulation and the polar climate system, and plays a significant role as the bridge communicating low- and high-latitude climatic processes. High-resolution multi-proxy analysis of a robust accelerator mass spectrometry (AMS) 14 C dated lacustrine sediment core recovered from Jingpo Lake in Northeastern China provides a detailed history of EASM variability and vegetation changes since ~5100 cal. yr BP. The period from ~5100 to 3600 cal. yr BP was characterized by the highest pollen percentages of Quercus, Ulmus, Juglans and Corylopsis ; low Md (median grain size diameter); and high 13 C org values, reflecting a relatively warm and humid period. The period between ~3600 and 2100 cal. yr BP is characterized by high Md and low 13 C org values, and a rapid increase in pollen percentages of herbs, indicating cool and dry climatic conditions. From ~2100 to 150 cal. yr BP, a gradual increase in 13 C org values and low Md values, and a rapid increase in Carpinus, Juglans and Corylopsis pollen percentages was observed, indicating climate change towards warmer and wetter conditions. After ~150 cal. yr BP, the highest values of total organic carbon mass accumulation rate (TOC-MAR), total nitrogen mass accumulation rate (TN-MAR) and magnetic susceptibility suggesting that the Jingpo Lake region has been severely affected by human activities. The EASM variability in Northeastern China during the mid- to late Holocene shows trends similar to EASM records in China. Furthermore, our findings indicate that the variability of the EASM during the mid- to late Holocene on the multi-decadal to centennial scale was forced by changes in both solar output and oceanic–atmospheric circulation interaction.

Description: Author(s): J. Shan, W. Shi, L. Y. Liu, Y. R. Shen, and L. Xu Gold nanoparticles deposited on the windows of a liquid crystal (LC) cell were found to be able to reduce the surface anchoring energy of the LC, and hence the threshold for its reorientation phase transition, by 1 to 2 orders of magnitude when a cw pump light was used to excite the local plasmon re... [Phys. Rev. Lett. 109, 147801] Published Tue Oct 02, 2012

Description: Author(s): Rui-Qiang Wang, R. Shen, Shi-Liang Zhu, Baigeng Wang, and D. Y. Xing In a scanning tunneling microscope configuration (STM), we study theoretically the effects of quantum tunneling of magnetization (QTM) as well as transport-induced spin relaxation on the electron transport through a single-molecule magnet deposited on a metallic surface. It is shown that for the STM... [Phys. Rev. B 85, 165432] Published Mon Apr 16, 2012

Description: Author(s): Wei Chen, R. Shen, L. Sheng, B. G. Wang, and D. Y. Xing We propose a promising electron entanglement detector consisting of two quantum spin Hall systems weakly coupled to a superconductor. The detection of electron spins along various polarization directions, which is a prerequisite for testing Bell’s inequality on solid state spins, can be achieved in ... [Phys. Rev. Lett. 109, 036802] Published Fri Jul 20, 2012

Description: In this study, we developed a simple and efficient Bacillus subtilis genome editing method in which targeted gene(s) could be inactivated by single-stranded PCR product(s) flanked by short homology regions and in-frame deletion could be achieved by incubating the transformants at 42°C. In this process, homologous recombination (HR) was promoted by the lambda beta protein synthesized under the control of promoter P RM in the lambda cI857 P RM –P R promoter system on a temperature sensitive plasmid pWY121. Promoter P R drove the expression of the recombinase gene cre at 42°C for excising the floxed ( lox sites flanked) disruption cassette that contained a bleomycin resistance marker and a heat inducible counter-selectable marker ( hewl , encoding hen egg white lysozyme). Then, we amplified the single-stranded disruption cassette using the primers that carried 70 nt homology extensions corresponding to the regions flanking the target gene. By transforming the respective PCR products into the B. subtilis that harbored pWY121 and incubating the resultant mutants at 42°C, we knocked out multiple genes in the same genetic background with no marker left. This process is simple and efficient and can be widely applied to large-scale genome analysis of recalcitrant Bacillus species.