Catalytic CO Oxidation on the Cu+-Ov-Ce3+ Interface Constructed by an Electrospinning Method for Enhanced CO Adsorption at Low Temperature.

It is crucial to eliminate CO emissions using non-noble catalysts. Cu-based catalysts have been widely applied in CO oxidation, but their activity and stability at low temperatures are still challenging. This study reports the preparation and application of an efficient copper-doped ceria electrospun fiber catalyst prepared by a facile electrospinning method. The obtained 10Cu-Ce fiber catalyst achieved complete CO oxidation at a temperature as low as 90 °C. However, a reference 10Cu/Ce catalyst prepared by the impregnation method needed 110 °C to achieve complete CO oxidation under identical reaction conditions. Asymmetric oxygen vacancies (ASOV) at the interface between copper and cerium were constructed, to effectively absorb gas molecules involved in the reaction, leading to the enhanced oxidation of CO. The exceptional ability of the 10Cu-Ce catalyst to adsorb CO is attributed to its unique structure and surface interaction phase Cu+-Ov-Ce3+, as demonstrated by a series of characterizations and DFT calculations. This novel approach of using electrospinning offers a promising technique for developing low-temperature and non-noble metal-based catalysts.

The chloroplast genome of a unicellular green alga strain isolated from the rubber processing wastewater.

Chlorella vulgaris ITBBA3-12 has a role in the purification of the rubber processing wastewater. Its complete chloroplast genome contains 168369 bp, with a G + C content of 33.0%. A total of 147 genes were annotated, including 113 protein-coding genes, three rRNA (rrn23, rrn16, and rrn5) genes, and 31 tRNA genes. The significant feature of the chloroplast genome is that the genes encoding subunit V (petG), VI (petL), and apocytochrome f (petA) of the cytochrome b6/f complex are in triplicate, which was not observed in the other C. vulgaris strains. Phylogenetic analysis using the chloroplast genomes of Chlorophyta species indicated that ITBBA3-12 is closely related to C. vulgaris strain UTEX259 and NJ-7, and they clustered in the Chlorella lineage.

De novo assembly, transcriptome characterization, and simple sequence repeat marker development in duckweed Lemna gibba.

Lemna gibba is a species of duckweed showing great potential in bioenergy production and wastewater treatment. However, the relevant transcriptomic and genomic resources are very limited for this species, which dramatically hinders its genetic diversity and genome mapping researches. In this work, ~ 233.5 million clean reads were generated from L. gibba by Illumina paired-end sequencing, and subsequently they were de novo assembled into 131,870 unigenes, of which 61,622 were annotated and 43,319 were expressed with Fragments Per Kilobase of transcript per Million fragments mapped (FPKM) > 5. In total, 19,297 simple sequence repeats (SSRs) were identified from 15,261 SSR-containing unigenes. Dinucleotide (78.4%) were the most abundant SSRs, followed by tri- (14.9%), tetra- (4.1%), and penta-nucleotides (1.5%). The top three motifs were AG/CT (69.9%), AC/GT (6.5%), and ATC/ATG (4.9%). Further analysis revealed that the presence of SSR motif was independent of the expression level for a given gene. Based on the sequence of these SSR-containing unigenes, a total of 10,292 SSR markers were developed, of which only 2671 were further retained after removing those derived from unannotated or extra-low expressed (e.g., FPKM ≤ 5) unigenes. Finally, a subset of 70 SSR markers was randomly selected and examined in nine diverse L. gibba genotypes for the PCR amplification and polymorphism, as well as in other duckweed species for the inter-specifically amplifiability. This work is the first report on the transcriptome-based large-scale SSR markers development and analysis in L. gibba. The transcriptome generated and the SSR markers developed in this work will provide a valuable resource for genetic diversity assessment in L. gibba and also for species relationship investigation in Lemnaceae family.

Genome-wide discovery and functional prediction of salt-responsive lncRNAs in duckweed.

BACKGROUND: Salt significantly depresses the growth and development of the greater duckweed, Spirodela polyrhiza, a model species of floating aquatic plants. Physiological responses of this plant to salt stress have been characterized, however, the roles of long noncoding RNAs (lncRNAs) remain unknown. RESULTS: In this work, totally 2815 novel lncRNAs were discovered in S. polyrhiza by strand-specific RNA sequencing, of which 185 (6.6%) were expressed differentially under salinity condition. Co-expression analysis indicated that the trans-acting lncRNAs regulated their co-expressed genes functioning in amino acid metabolism, cell- and cell wall-related metabolism, hormone metabolism, photosynthesis, RNA transcription, secondary metabolism, and transport. In total, 42 lncRNA-mRNA pairs that might participate in cis-acting regulation were found, and these adjacent genes were involved in cell wall, cell cycle, carbon metabolism, ROS regulation, hormone metabolism, and transcription factor. In addition, the lncRNAs probably functioning as miRNA targets were also investigated. Specifically, TCONS_00033722, TCONS_00044328, and TCONS_00059333 were targeted by a few well-studied salt-responsive miRNAs, supporting the involvement of miRNA and lncRNA interactions in the regulation of salt stress responses. Finally, a representative network of lncRNA-miRNA-mRNA was proposed and discussed to participate in duckweed salt stress via auxin signaling. CONCLUSIONS: This study is the first report on salt-responsive lncRNAs in duckweed, and the findings will provide a solid foundation for in-depth functional characterization of duckweed lncRNAs in response to salt stress.

Asymmetric birth and death of type I and type II MADS-box gene subfamilies in the rubber tree facilitating laticifer development.

The rubber tree (Hevea brasiliensis Muell. Arg.) is a rubber producing crop and contains specialized laticifers. MADS-box genes are a family of transcription factor genes that regulate plant development, especially floral organ and gametophyte development. 97 MADS-box genes were identified in the rubber tree through transcriptomes and genome mining. 93.8% of the genes were mapped onto the genome scaffolds in correspondence to the coverage (93.8%) of current version of sequenced genome. Phylogenetic analysis indicates that type II MADS-box genes have been more actively duplicated than their orthologous genes in Arabidopsis and rice, so that most (70, 72.2%) of the MADS-box genes in the rubber tree belong to type II subfamily. This is a high percentage compared to those in Arabidopsis (43.7%) and rice (56.8%). Moreover, 69 out of 70 type II genes in the rubber tree are transcribed, and they are mostly predominantly expressed in flowers, but some genes are predominantly expressed in laticifers, suggesting their roles in both flower and laticifer development. The number of type I genes in the rubber tree is only 27 (27.8%), a much smaller number compared to their orthologous genes in Arabidopsis (56.3%) and rice (43.2%). At the same time, most of the type I genes (55.6%, 15) in the rubber tree are silent and are probably pseudogenes. The high birth rate and low death rate of type II genes and low birth rate and high death rate of type I genes may corresponds to special developmental requirements in the rubber tree, e.g. the development of laticifer system for biosynthesis of cis-polyisoprene, the rubber. Moreover, atypical MIKC* factors (e.g. HbMADS1 in S-clade, and HbMADS20 in P-clade) are identified. These genes are diverged to typical MIKC* genes in sequences and facilitate functions required in laticifer development and rubber biosynthesis, which is not necessary in Arabidopsis and rice.

CO oxidative coupling to dimethyl oxalate over Pd-Me (Me = Cu, Al) catalysts: a combined DFT and kinetic study.

CO oxidative coupling to dimethyl oxalate (DMO) on Pd(111), Pd-Cu(111) and Pd-Al(111) surfaces was systematically investigated by means of density functional theory (DFT) together with periodic slab models and micro-kinetic modeling. The binding energy results show that Cu and Al can be fine substrates to stably support Pd. The favorable pathway for DMO synthesis on these catalysts starts from the formation of two COOCH3 intermediates, followed by the coupling to each other, and the catalytic activity follows the trend of Pd-Al(111) > Pd(111) > Pd-Cu(111). Additionally, the formation of DMO is far favorable than that of dimethyl carbonate (DMC) on these catalysts. The results were further demonstrated by micro-kinetic modeling. Therefore, Pd-Al bimetallic catalysts can be applied in practice to effectively enhance the catalytic performance and greatly reduce the cost. This study can help with fine-tuning and designing of high-efficient and low-cost Pd-based bimetallic catalysts.

Flower induction, microscope-aided cross-pollination, and seed production in the duckweed Lemna gibba with discovery of a male-sterile clone.

Duckweed species have a great potential to develop into fast-growing crops for water remediation and bioenergy production. Seed production and utilization of hybrid vigour are essential steps in this process. However, even in the extensively-studied duckweed species, Lemna gibba, flower primordia were often aborted prior to maturation. Salicylic acid (SA) and agar solidification of the medium promoted flower maturation and resulted in high flowering rates in L. gibba 7741 and 5504. Artificial cross-pollination between individuals of L. gibba 7741 yielded seeds at high frequencies unlike that in L. gibba 5504. In contrast to clone 7741, the anthers of 5504 did not dehisce upon maturation, its artificially released pollen grains had pineapple-like exine with tilted spines. These pollens were not stained by 2,5-diphenylmonotetrazoliumbromide (MTT) and failed to germinate. Therefore, clone 5504 is male sterile and has potential application with respect to hybrid vigour. Moreover, pollination of flowers of 5504 with 7741 pollen grains resulted in intraspecific hybrid seeds, which was confirmed by inter-simple sequence repeat (ISSR) markers. These hybrid seeds germinated at a high frequency, forming new clones.

Interspecies and Intraspecies Analysis of Trehalose Contents and the Biosynthesis Pathway Gene Family Reveals Crucial Roles of Trehalose in Osmotic-Stress Tolerance in Cassava.

Trehalose is a nonreducing α,α-1,1-disaccharide in a wide range of organisms, and has diverse biological functions that range from serving as an energy source to acting as a protective/signal sugar. However, significant amounts of trehalose have rarely been detected in higher plants, and the function of trehalose in the drought-tolerant crop cassava (Manihot esculenta Crantz) is unclear. We measured soluble sugar concentrations of nine plant species with differing levels of drought tolerance and 41 cassava varieties using high-performance liquid chromatography with evaporative light-scattering detector (HPLC-ELSD). Significantly high amounts of trehalose were identified in drought-tolerant crops cassava, Jatropha curcas, and castor bean (Ricinus communis). All cassava varieties tested contained high amounts of trehalose, although their concentrations varied from 0.23 to 1.29 mg·g(-1) fresh weight (FW), and the trehalose level was highly correlated with dehydration stress tolerance of detached leaves of the varieties. Moreover, the trehalose concentrations in cassava leaves increased 2.3-5.5 folds in response to osmotic stress simulated by 20% PEG 6000. Through database mining, 24 trehalose pathway genes, including 12 trehalose-6-phosphate synthases (TPS), 10 trehalose-6-phosphate phosphatases (TPP), and two trehalases were identified in cassava. Phylogenetic analysis indicated that there were four cassava TPS genes (MeTPS1-4) that were orthologous to the solely active TPS gene (AtTPS1 and OsTPS1) in Arabidopsis and rice, and a new TPP subfamily was identified in cassava, suggesting that the trehalose biosynthesis activities in cassava had potentially been enhanced in evolutionary history. RNA-seq analysis indicated that MeTPS1 was expressed at constitutionally high level before and after osmotic stress, while other trehalose pathway genes were either up-regulated or down-regulated, which may explain why cassava accumulated high level of trehalose under normal conditions. MeTPS1 was then transformed into tobacco (Nicotiana benthamiana). Results indicated that transgenic tobacco lines accumulated significant level of trehalose and possessed improved drought stress tolerance. In conclusion, cassava accumulated significantly high amount of trehalose under normal conditions due to multiplied trehalose biosynthesis gene families and constant expression of the active MeTPS1 gene. High levels of trehalose subsequently contributed to high drought stress tolerance.

Arabidopsis Myrosinase Genes AtTGG4 and AtTGG5 Are Root-Tip Specific and Contribute to Auxin Biosynthesis and Root-Growth Regulation.

Plant myrosinases (ß-thioglucoside glucohydrolases) are classified into two subclasses, Myr I and Myr II. The biological function of Myr I has been characterized as a major biochemical defense against insect pests and pathogens in cruciferous plants. However, the biological function of Myr II remains obscure. We studied the function of two Myr II member genes AtTGG4 and AtTGG5 in Arabidopsis. RT-PCR showed that both genes were specifically expressed in roots. GUS-assay revealed that both genes were expressed in the root-tip but with difference: AtTGG4 was expressed in the elongation zone of the root-tip, while AtTGG5 was expressed in the whole root-tip. Moreover, myrosin cells that produce and store the Myr I myrosinases in aboveground organs were not observed in roots, and AtTGG4 and AtTGG5 were expressed in all cells of the specific region. A homozygous double mutant line tgg4tgg5 was obtained through cross-pollination between two T-DNA insertion lines, tgg4E8 and tgg5E12, by PCR-screening in the F2 and F3 generations. Analysis of myrosinase activity in roots of mutants revealed that AtTGG4 and AtTGG5 had additive effects and contributed 35% and 65% myrosinase activity in roots of the wild type Col-0, respectively, and myrosinase activity in tgg4tgg5 was severely repressed. When grown in Murashiege & Skoog (MS) medium or in soil with sufficient water, Col-0 had the shortest roots, and tgg4tgg5 had the longest roots, while tgg4E8 and tgg5E12 had intermediate root lengths. In contrast, when grown in soil with excessive water, Col-0 had the longest roots, and tgg4tgg5 had the shortest roots. These results suggested that AtTGG4 and AtTGG5 regulated root growth and had a role in flood tolerance. The auxin-indicator gene DR5::GUS was then introduced into tgg4tgg5 by cross-pollination. DR5::GUS expression patterns in seedlings of F1, F2, and F3 generations indicated that AtTGG4 and AtTGG5 contributed to auxin biosynthesis in roots. The proposed mechanism is that indolic glucosinolate is transported to the root-tip and converted to indole-3-acetonitrile (IAN) in the tryptophan-dependent pathways by AtTGG4 and AtTGG5, and IAN is finally converted to indole-3-acetic acid (IAA) by nitrilases in the root-tip. This mechanism guarantees the biosynthesis of IAA in correct cells of the root-tip and, thus, a correct auxin gradient is formed for healthy development of roots.

Genomic Instability Associated with p53 Knockdown in the Generation of Huntington's Disease Human Induced Pluripotent Stem Cells.

Alterations in DNA damage response and repair have been observed in Huntington's disease (HD). We generated induced pluripotent stem cells (iPSC) from primary dermal fibroblasts of 5 patients with HD and 5 control subjects. A significant fraction of the HD iPSC lines had genomic abnormalities as assessed by karyotype analysis, while none of our control lines had detectable genomic abnormalities. We demonstrate a statistically significant increase in genomic instability in HD cells during reprogramming. We also report a significant association with repeat length and severity of this instability. Our karyotypically normal HD iPSCs also have elevated ATM-p53 signaling as shown by elevated levels of phosphorylated p53 and H2AX, indicating either elevated DNA damage or hypersensitive DNA damage signaling in HD iPSCs. Thus, increased DNA damage responses in the HD genotype is coincidental with the observed chromosomal aberrations. We conclude that the disease causing mutation in HD increases the propensity of chromosomal instability relative to control fibroblasts specifically during reprogramming to a pluripotent state by a commonly used episomal-based method that includes p53 knockdown.

Physiological Investigation and Transcriptome Analysis of Polyethylene Glycol (PEG)-Induced Dehydration Stress in Cassava.

Cassava is an important tropical and sub-tropical root crop that is adapted to drought environment. However, severe drought stress significantly influences biomass accumulation and starchy root production. The mechanism underlying drought-tolerance remains obscure in cassava. In this study, changes of physiological characters and gene transcriptome profiles were investigated under dehydration stress simulated by polyethylene glycol (PEG) treatments. Five traits, including peroxidase (POD) activity, proline content, malondialdehyde (MDA), soluble sugar and soluble protein, were all dramatically induced in response to PEG treatment. RNA-seq analysis revealed a gradient decrease of differentially expressed (DE) gene number in tissues from bottom to top of a plant, suggesting that cassava root has a quicker response and more induced/depressed DE genes than leaves in response to drought. Overall, dynamic changes of gene expression profiles in cassava root and leaves were uncovered: genes related to glycolysis, abscisic acid and ethylene biosynthesis, lipid metabolism, protein degradation, and second metabolism of flavonoids were significantly induced, while genes associated with cell cycle/organization, cell wall synthesis and degradation, DNA synthesis and chromatin structure, protein synthesis, light reaction of photosynthesis, gibberelin pathways and abiotic stress were greatly depressed. Finally, novel pathways in ABA-dependent and ABA-independent regulatory networks underlying PEG-induced dehydration response in cassava were detected, and the RNA-Seq results of a subset of fifteen genes were confirmed by real-time PCR. The findings will improve our understanding of the mechanism related to dehydration stress-tolerance in cassava and will provide useful candidate genes for breeding of cassava varieties better adapted to drought environment.

Identification and Evolution of Functional Alleles of the Previously Described Pollen Specific Myrosinase Pseudogene AtTGG6 in Arabidopsis thaliana.

Myrosinases are ß-thioglucoside glucohydrolases and serve as defense mechanisms against insect pests and pathogens by producing toxic compounds. AtTGG6 in Arabidopsis thaliana was previously reported to be a myrosinase pseudogene but specifically expressed in pollen. However, we found that AlTGG6, an ortholog to AtTGG6 in A. lyrata (an outcrossing relative of A. thaliana) was functional, suggesting that functional AtTGG6 alleles may still exist in A. thaliana. AtTGG6 alleles in 29 A. thaliana ecotypes were cloned and sequenced. Results indicate that ten alleles were functional and encoded Myr II type myrosinase of 512 amino acids, and myrosinase activity was confirmed by overexpressing AtTGG6 in Pichia pastoris. However, the 19 other ecotypes had disabled alleles with highly polymorphic frame-shift mutations and diversified sequences. Thirteen frame-shift mutation types were identified, which occurred independently many times in the evolutionary history within a few thousand years. The functional allele was expressed specifically in pollen similar to the disabled alleles but at a higher expression level, suggesting its role in defense of pollen against insect pests such as pollen beetles. However, the defense function may have become less critical after A. thaliana evolved to self-fertilization, and thus resulted in loss of function in most ecotypes.

PARK2 patient neuroprogenitors show increased mitochondrial sensitivity to copper.

Poorly-defined interactions between environmental and genetic risk factors underlie Parkinson's disease (PD) etiology. Here we tested the hypothesis that human stem cell derived forebrain neuroprogenitors from patients with known familial risk for early onset PD will exhibit enhanced sensitivity to PD environmental risk factors compared to healthy control subjects without a family history of PD. Two male siblings (SM and PM) with biallelic loss-of-function mutations in PARK2 were identified. Human induced pluripotent stem cells (hiPSCs) from SM, PM, and four control subjects with no known family histories of PD or related neurodegenerative diseases were utilized. We tested the hypothesis that hiPSC-derived neuroprogenitors from patients with PARK2 mutations would show heightened cell death, mitochondrial dysfunction, and reactive oxygen species generation compared to control cells as a result of exposure to heavy metals (PD environmental risk factors). We report that PARK2 mutant neuroprogenitors showed increased cytotoxicity with copper (Cu) and cadmium (Cd) exposure but not manganese (Mn) or methyl mercury (MeHg) relative to control neuroprogenitors. PARK2 mutant neuroprogenitors also showed a substantial increase in mitochondrial fragmentation, initial ROS generation, and loss of mitochondrial membrane potential following Cu exposure. Our data substantiate Cu exposure as an environmental risk factor for PD. Furthermore, we report a shift in the lowest observable effect level (LOEL) for greater sensitivity to Cu-dependent mitochondrial dysfunction in patients SM and PM relative to controls, correlating with their increased genetic risk for PD.