Phosphorus Efficiency Mechanisms of Two Wheat Cultivars as Affected by a Range of Phosphorus Levels in the Field.

Phosphorus (P) efficiency includes both P acquisition efficiency (PAE) and internal P utilization efficiency (PUE). Despite substantial research, genotypic variation in PAE and PUE remains incompletely understood in the field. A 2-year field study was conducted to compare PAE and PUE and related morphological, physiological, and molecular root traits of two winter wheat cultivars (Triticum aestivum L. cv. SJZ8 and KN92) in response to six P application rates in a P-deficient calcareous soil. Both cultivars showed similar growth and yield potential at each P supply level, reaching optimal growth at the same P application rate of about 100 kg P ha-1. However, the two cultivars differed in how they achieved yield and P efficiency. As P supply increased for both cultivars, root dry weight (RDW), root length density, and expression of the phosphate transporter gene TaPHT1.2 in roots initially increased and then stabilized, but arbuscular mycorrhizal fungal colonization, rhizosphere acid phosphatase activity, expressions of the P-starvation marker gene TaIPS1.1 and the purple acid phosphatase gene TaPAP16 in roots initially decreased and then stabilized. To enhance P acquisition when the P supply was deficient, KN92 modified the morphology of its roots, while SJZ8 increased the physiological activities in its roots. With an adequate P supply, high expression of TaPHT1.2 in roots might account for efficient P uptake for both cultivars, especially for KN92. Although P uptake per RDW was similar for both cultivars at anthesis, PAE was higher for KN92 than SJZ8 in terms of total P uptake in aboveground parts, whereas shoot and grain PUE were higher in SJZ8 than in KN92, mainly during the reproductive growth stage. These results indicate that P efficiency is under genotypic control at all P supply levels tested in both wheat cultivars, and that the two cultivars depend on different root strategies for P acquisition and utilization in response to changes in the P supply.

Harvesting more grain zinc of wheat for human health.

Increasing grain zinc (Zn) concentration of cereals for minimizing Zn malnutrition in two billion people represents an important global humanitarian challenge. Grain Zn in field-grown wheat at the global scale ranges from 20.4 to 30.5 mg kg-1, showing a solid gap to the biofortification target for human health (40 mg kg-1). Through a group of field experiments, we found that the low grain Zn was not closely linked to historical replacements of varieties during the Green Revolution, but greatly aggravated by phosphorus (P) overuse or insufficient nitrogen (N) application. We also conducted a total of 320-pair plots field experiments and found an average increase of 10.5 mg kg-1 by foliar Zn application. We conclude that an integrated strategy, including not only Zn-responsive genotypes, but of a similar importance, Zn application and field N and P management, are required to harvest more grain Zn and meanwhile ensure better yield in wheat-dominant areas.

Utilization of a Wheat660K SNP array-derived high-density genetic map for high-resolution mapping of a major QTL for kernel number.

In crop plants, a high-density genetic linkage map is essential for both genetic and genomic researches. The complexity and the large size of wheat genome have hampered the acquisition of a high-resolution genetic map. In this study, we report a high-density genetic map based on an individual mapping population using the Affymetrix Wheat660K single-nucleotide polymorphism (SNP) array as a probe in hexaploid wheat. The resultant genetic map consisted of 119 566 loci spanning 4424.4 cM, and 119 001 of those loci were SNP markers. This genetic map showed good collinearity with the 90 K and 820 K consensus genetic maps and was also in accordance with the recently released wheat whole genome assembly. The high-density wheat genetic map will provide a major resource for future genetic and genomic research in wheat. Moreover, a comparative genomics analysis among gramineous plant genomes was conducted based on the high-density wheat genetic map, providing an overview of the structural relationships among theses gramineous plant genomes. A major stable quantitative trait locus (QTL) for kernel number per spike was characterized, providing a solid foundation for the future high-resolution mapping and map-based cloning of the targeted QTL.

Genome-wide Identification, Characterization, and Expression Analysis of PHT1 Phosphate Transporters in Wheat.

The PHT1 family of phosphate (Pi) transporters mediates phosphorus (P) uptake and re-mobilization in plants. A genome-wide sequence analysis of PHT1 genes in wheat (Triticum aestivum) was conducted, and their expression locations and responses to P availability were further investigated. We cloned 21 TaPHT1 genes from the homologous alleles at TaPHT1.1 to 1.10 through screening a BAC library and amplifying genomic sequences. The TaPHT1 transporters were clustered into five branches in the phylogenetic tree of PHT1 proteins, and the TaPHT1 genes from a given branch shared high similarities in sequences, expression locations, and responses to P availability. The seven tested PHT1 genes all showed Pi-transport activity in yeast (Saccharomyces cerevisiae) cells grown under both low Pi and high Pi conditions. The expression of TaPHT1.1/1.9, 1.2, and 1.10 were root specific. The expression of these TaPHT1 genes at flowering positively correlated with P uptake after stem elongation across three P application rates and two wheat varieties in a field experiment. Therefore, modification of PHT1 expression may improve P use efficiency in a broad regime of P availability.

A Study on Synthesis of CaAl12O19∶xMn4+ Red Phosphor with Combustion Method.

The CaAl12O19∶xMn4+ phosphor was rapidly synthesized at low temperatures with combustion method with urea as combustion agent. The influence of calcination temperature and time, the doping amount of Mn4+ ions, the molar ratio of combustion agent to CaAl12O19, on luminous intensity of fluorescent powder were examined with orthogonal analytical method. The optimum conditions for preparing phosphors are: sintering temperature 1 200 ℃, the amount of Mn4+ 0.02, the molar ratio of combustion agent to CaAl12O19 50∶1, and sintering time 5 hrs. The corresponding luminous intensity of this powder was 95.8, which is the largest. The phosphor shows a strong red luminescence at the 643 and 656 nm due to the 2E­4A2 transition of the Mn4+. The maximum excitation peak was at 470 nm due to the 4A2­4T2 transition of Mn4+ ligand field. The 470 nm excitation peak was matched with the 465 nm emission of the LED chips.

[Syntheses and luminescence investigation of CaAl12O19:xMn(4+) red phosphors].

CaAl12O19:xMn(4+) (x=0.0~0.00184 mol) red phosphors were prepared by high-temperature solid state method. Different influencing factors, i. e. the doping amount of Mn(4+), and sintering temperature, were investigated by the orthogonal experiment design. The optimum conditions for preparing CaAl12O19:xMn(4+) phosphors are: sintering temperature 1500 °C, and x=0.0147 mol. It emits strong deep red light with emission maximal peak at 656 nm, and two shoulder peaks (643 and 666 nm), the corresponding excitation peak is located at 470 nm. The 656 nm emission peak is ascribed to the (2)E-->(4)A2 transition, and the shoulder peaks (643 and 666 nm) are attributed to phonon sideband transitions. The 470 nm excitation peak is ascribed to the ligand-field (4)A2-->(4)T2 transition (d-->d band). Owing to the fact that the excitation peak (470 nm) is near the emission (460 nm) of commercial LED chips, it is quite suitable for red light candidate for LED light resources.

Characterization of root response to phosphorus supply from morphology to gene analysis in field-grown wheat.

The adaptations of root morphology, physiology, and biochemistry to phosphorus supply have been characterized intensively. However, characterizing these adaptations at molecular level is largely neglected under field conditions. Here, two consecutive field experiments were carried out to investigate the agronomic traits and root traits of wheat (Triticum aestivum L.) at six P-fertilizer rates. Root samples were collected at flowering to investigate root dry weight, root length density, arbusular-mycorrhizal colonization rate, acid phosphatase activity in rhizosphere soil, and expression levels of genes encoding phosphate transporter, phosphatase, ribonucleases, and expansin. These root traits exhibited inducible, inhibitory, or combined responses to P deficiency, and the change point for responses to P supply was at or near the optimal P supply for maximum grain yield. This research improves the understanding of mechanisms of plant adaptation to soil P in intensive agriculture and provides useful information for optimizing P management based on the interactions between soil P dynamics and root processes.

[The synthesis and luminescence measurement of YAG : Ce3+ phosphors by high temperature solid phase method].

YAG : Ce3+ luminescence materials were prepared by a high-temperature solid state method. Different influencing factors, e. g., the doping amount of Ce3+, sintering temperature, and sintering time, were investigated by the orthogonal experiment method. The results showed that: (1) the influence of three factors on light-emitting intensity of YAG : Ce3+ phosphors is in the following order, sintering temperature >> sintering time > the doping amount of Ce3+; (2) the optimum conditions for YAG : Ce3+ phosphors are: sintering temperature 1 600 degrees C, the doping amount of Ce3+ 0.10 mol, and sintering time 4 h. Under these conditions, the light-emitting intensity of YAG : Ce3+ phosphors prepared is the largest. Furthermore, another optimum conditions are: sintering temperature 1 600 degrees C, the doping amount of Ce3+ 0.08 mol, and sintering time 4 h, and the YAG : Ce3+ phosphors prepared are also excellent based on them. The transition properties and spectral features of excitation and luminescence spectra of these synthesized phosphors were analyzed in detail and assigned as Ce3+ 4f-5d transition.

[Influence of La2O3 and Li2O on glass powder for infiltrating ZTA all-ceramic dental material formed by gel-casting].

PURPOSE: The influence of La2O3 and Li2O on glass powder was studied in this paper, which is to infiltrate ZTA all-ceramic dental material formed by gel-casting. The performance of different component was analyzed to optimize glass formula. METHODS: Six groups of glass powder were designed and prepared by conventional melt-quenching method. ZTA ceramic blocks were covered with glass paste, which were formed by gel-casting and sintered in 1200 degrees centigrade, then infiltrated in 1150 degrees centigrade for twice to make glass/ZTA ceramic composites. By detecting differential thermal analysis and melting range of infiltration glass power, as well as flexural strength, linear shrinkage, SEM and EDS of glass/ZTA ceramic composites, the optimized glass group was determined out. Statistical analysis was performed using SPSS 13.0 software package by means of paired t test or one way ANOVA. RESULTS: The bending strength of group Li1 was (291.2±27.9) MPa, significantly higher than group Li2 and group La2(P<0.05), and linear shrinkage of group Li1 was only(1.85±0.27)%. SEM and EDS showed glass of group Li1 can lubricate ZTA ceramics well, their structure was compact and had a few small pores. Intergranular fracture existed on cross surface as well as transgranular fracture. CONCLUSIONS: The results showed that Li1(30%La2O3-15%Al2O3-15%SiO2-15%B2O3-5%Li2O) glass infiltrated ZTA ceramic composite had the best capability. Glass/ZTA composite material can be prepared by gel-casting and infiltrating way, and this process is simple and economically suitable for general dental laboratory.

3,5-Dicarboxypyridinium fluoride.

The cation of the title salt, C(7)H(6)NO(4) (+.)F(-), lies on a twofold rotation axis that passes through the N and 4-C atoms of the pyridine ring; the carb-oxy-lic acid substituent features unambiguous carbon-oxygen single and double bonds. The fluoride ion is a hydrogen-bond acceptor to two hy-droxy and one amino groups, these O-H⋯F and N-H⋯F hydrogen bonds leading to the formation of a layer structure parallel to the ab plane. The F atom lies on a position of 2 site symmetry.

Theoretical studies of molecular structure, electronic structure, spectroscopic properties and the ancillary ligand effect: a comparison of tris-chelate ML3-type and ML2X-type species for gallium(III) complexes with N,O-donor phenolic ligand, 2-(2-hydroxyphenyl)benzothiazole.

Two Ga(III) complexes with main ligand, 2-(2-hydroxyphenyl)benzothiazole (HL'), namely mixed-ligand ML2X-type [GaL'2X'] (1) (HX'=acetic acid, as ancillary ligand) and the meridianal tris-chelate [GaL'3] (2) have been investigated by the density functional theory (DFT/TDDFT) level calculations. Both 1 and 2 can be presented as a similar "mixed-ligand ML2X-type" species. The molecular geometries, electronic structures, metal-ligand bonding property of Ga-O (N) (main ligand), Ga-O (N) (ancillary ligand) interactions, and the ancillary ligand effect on their HOMO-LUMO gap, their absorption/emission property, and their absorption/emission wavelengths/colors for them have been discussed in detail based on the orbital interactions, the partial density of states (PDOS), and so on. The current investigation also indicates that it is quite probable that by introduction of different ancillary ligands, a series of new mixed-ligand ML2X-type complexes for group 13 metals can be designed with their absorption/emission property and the absorption/emission wavelengths and colors being tuned.

Haplotype analysis of the genes encoding glutamine synthetase plastic isoforms and their association with nitrogen-use- and yield-related traits in bread wheat.

Glutamine synthetase (GS) plays a key role in the growth, nitrogen (N) use and yield potential of cereal crops. Investigating the haplotype variation of GS genes and its association with agronomic traits may provide useful information for improving wheat N-use efficiency and yield. We isolated the promoter and coding region sequences of the plastic glutamine synthetase isoform (GS2) genes located on chromosomes 2A, 2B and 2D in bread wheat. By analyzing nucleotide sequence variations of the coding region, two, six and two haplotypes were distinguished for TaGS2-A1 (a and b), TaGS2-B1 (a-f) and TaGS2-D1 (a and b), respectively. By analyzing the frequency data of different haplotypes and their association with N use and agronomic traits, four major and favorable TaGS2 haplotypes (A1b, B1a, B1b, D1a) were revealed. These favorable haplotypes may confer better seedling growth, better agronomic performance, and improved N uptake during vegetative growth or grain N concentration. Our data suggest that certain TaGS2 haplotypes may be valuable in breeding wheat varieties with improved agronomic performance and N-use efficiency.

Gene structure and expression of the high-affinity nitrate transport system in rice roots.

Rice has a preference for uptake of ammonium over nitrate and can use ammonium-N efficiently. Consequently, transporters mediating ammonium uptake have been extensively studied, but nitrate transporters have been largely ignored. Recently, some reports have shown that rice also has high capacity to acquire nitrate from growth medium, so understanding the nitrate transport system in rice roots is very important for improving N use efficiency in rice. The present study identified four putative NRT2 and two putative NAR2 genes that encode components of the high-affinity nitrate transport system (HATS) in the rice (Oryza sativa L. subsp. japonica cv. Nipponbare) genome. OsNRT2.1 and OsNRT2.2 share an identical coding region sequence, and their deduced proteins are closely related to those from mono-cotyledonous plants. The two NAR2 proteins are closely related to those from mono-cotyledonous plants as well. However, OsNRT2.3 and OsNRT2.4 are more closely related to Arabidopsis NRT2 proteins. Relative quantitative reverse transcription-polymerase chain reaction analysis showed that all of the six genes were rapidly upregulated and then downregulated in the roots of N-starved rice plants after they were re-supplied with 0.2 mM nitrate, but the response to nitrate differed among gene members. The results from phylogenetic tree, gene structure and expression analysis implied the divergent roles for the individual members of the rice NRT2 and NAR2 families. High-affinity nitrate influx rates associated with nitrate induction in rice roots were investigated and were found to be regulated by external pH. Compared with the nitrate influx rates at pH 6.5, alkaline pH (pH 8.0) inhibited nitrate influx, and acidic pH (pH 5.0) enhanced the nitrate influx in 1 h nitrate induced roots, but did not significantly affect that in 4 to 8 h nitrate induced roots.

A CDC25 homologue from rice functions as an arsenate reductase.

Enzymatic reduction of arsenate to arsenite is the first step in arsenate metabolism in all organisms studied. The rice genome contains two ACR2-like genes, OsACR2.1 and OsACR2.2, which may be involved in regulating arsenic metabolism in rice. Here, we cloned both OsACR2 genes and expressed them in an Escherichia coli strain in which the arsC gene was deleted and in a yeast (Saccharomyces cerevisiae) strain with a disrupted ACR2 gene. OsACR2.1 complemented the arsenate hypersensitive phenotype of E. coli and yeast. OsACR2.2 showed much less ability to complement. The gene products were purified and demonstrated to reduce arsenate to arsenite in vitro, and both exhibited phosphatase activity. In agreement with the complementation results, OsACR2.1 exhibited higher reductase activity than OsACR2.2. Mutagenesis of cysteine residues in the putative active site HC(X)(5)R motif led to nearly complete loss of both phosphatase and arsenate reductase activities. In planta expression of OsACR2.1 increased dramatically after exposure to arsenate. OsACR2.2 was observed only in roots following arsenate exposure, and its expression was less than OsACR2.1.

Phosphate (Pi) and arsenate uptake by two wheat (Triticum aestivum) cultivars and their doubled haploid lines.

BACKGROUND AND AIMS: Arsenic accumulation in cereal crops represents an important pathway for human exposure to arsenic from the environment. The objectives of the present work were to find whether the relationship between arsenate and phosphate (Pi) uptake rate differs among genotypes and to select genotypes with a low arsenate uptake rate with the aim of improving food safety and human health. METHODS: A hydroponic experiment was conducted using two wheat (Triticum aestivum) cultivars (Hanxuan 10 and Lumai 14) and ten doubled haploid (DH) lines derived from them to investigate Pi and arsenate uptake over 48 h. Ten plants were transferred to bottles containing 50 mL of pre-treatment solution containing 0.5 mM CaCl2 and 5 mM MES set at pH 6.0 with 330 microM Pi as KH2PO4 and 7.33 microM arsenate. The solutions were aerated continuously. At 8, 24 and 48 h after uptake, 1 mL of test solution was sampled for determination of Pi and arsenate concentrations. KEY RESULTS AND CONCLUSIONS: For each wheat line, Pi and arsenate concentrations in the test solution decreased with uptake time. Exponential (for Pi) or polynomial (for arsenate) regression plots fitted the data closely. For all genotypes, net Pi uptake rates decreased with time (from 0 to 48 h). However, net arsenate uptake rates decreased with time for D5, changed little with time for the male parent, D4 and D6, and increased with time for the others. An inflexion of about 25 microm Pi was observed for the relationship between arsenate and Pi concentrations in the test solution, indicating that 25 microm could be the point where the high-affinity uptake system 'switches on', or dominates over low-affinity uptake. In addition, the male parent, D1, D6 and D10 were considered ideal genotypes because they possess Pi transporters that discriminate strongly against arsenate and are expected to accumulate less arsenate in the field.

Arsenate (As) uptake by and distribution in two cultivars of winter wheat (Triticum aestivum L.).

Two cultivars of winter wheat (Triticum aestivum L.) (Jing 411 and Lovrin 10) were used to investigate arsenate (As) uptake and distribution in plants grown in hydroponic culture and in the soil. Results showed that without As addition, Lovrin 10 had higher biomass than Jing 411 in the soil pot experiment; in the hydroponic experiment Lovrin 10 had similar root biomass to and lower shoot biomass than Jing 411. Increasing P supply from 32 to 161 microM resulted in lower tissue As concentrations, and increasing As supply from 0 to 2,000 microM resulted in lower tissue P concentrations. Increasing P supply tended to increase shoot-to-root ratios of As concentrations, and increasing As supply tended to decrease shoot-to-root ratios of As concentrations. Both cultivars invested more in root production under P deficient conditions than under P sufficient conditions. Lovrin 10 invested more biomass production to roots than Jing 411, which might be partly responsible for higher shoot P and As concentrations and higher shoot-to-root ratios of As concentrations. Moreover, Lovrin 10 allocated less As to roots than Jing 411 and the difference disappeared with decreasing P supply.

Syntheses, structures, photoluminescence, and theoretical studies of a class of beryllium(II) compounds of aromatic N,O-chelate ligands.

Three members of a new class of luminescent, neutral, and monomeric Be(II) complexes of aromatic N,O-chelate ligands, namely [Be(pbm)(2)] (1), [Be(pbx)(2)] (2), and [Be(pbt)(2)] (3) [Hpbm = 2-(2'-hydroxylphenyl)benzimidazole, Hpbx = 2-(2'-hydroxylphenyl)benzoxazole, and Hpbt = 2-(2'-hydroxylphenyl)benzothiazole], have been prepared and characterized by X-ray crystallography and photoluminescence studies. All the complexes are neutral, mononuclear molecules and display strong photoluminescence in the blue/green region, and thus, they may serve as candidates for electroluminescence materials. The electronic transitions in the photoluminescent process have also been investigated by means of time-dependent density functional theory (TDDFT) energy level and molecular-orbital analyses, showing that their absorption and luminescent properties are ligand-based and ligand-tunable.

Characterization of arsenate reductase in the extract of roots and fronds of Chinese brake fern, an arsenic hyperaccumulator.

Root extracts from the arsenic (As) hyperaccumulating Chinese brake fern (Pteris vittata) were shown to be able to reduce arsenate to arsenite. An arsenate reductase (AR) in the fern showed a reaction mechanism similar to the previously reported Acr2p, an AR from yeast (Saccharomyces cerevisiae), using glutathione as the electron donor. Substrate specificity as well as sensitivity toward inhibitors for the fern AR (phosphate as a competitive inhibitor, arsenite as a noncompetitive inhibitor) was also similar to Acr2p. Kinetic analysis showed that the fern AR had a Michaelis constant value of 2.33 mM for arsenate, 15-fold lower than the purified Acr2p. The AR-specific activity of the fern roots treated with 2 mM arsenate for 9 d was at least 7 times higher than those of roots and shoots of plant species that are known not to tolerate arsenate. A T-DNA knockout mutant of Arabidopsis (Arabidopsis thaliana) with disruption in the putative Acr2 gene had no AR activity. We could not detect AR activity in shoots of the fern. These results indicate that (1) arsenite, the previously reported main storage form of As in the fern fronds, may come mainly from the reduction of arsenate in roots; and (2) AR plays an important role in the detoxification of As in the As hyperaccumulating fern.

Vacuolar compartmentalization: a second-generation approach to engineering plants for phytoremediation.

Engineering plants with greater metal tolerance and accumulation properties is the key to developing phytoremediators. A recent study by Won-Yong Song et al. has shown that overexpressing the yeast vacuolar transporter YCF1 increases Pb and Cd tolerance and consequently increases the accumulation of these metals in shoots of transgenic Arabidopsis plants even though expression levels of YCF1 were relatively low. This technology can be used to engineer advanced phytoremediators, increasing their ability to pump heavy metals into a safe compartment while requiring only a small amount of transporters rather than a large amount of chelating peptide material.