Oxidation and reduction of sulfite contribute to susceptibility and detoxification of SO2 in Populus × canescens leaves

Key Message

The critical level for SO ₂ susceptibility of Populus × canescens is approximately 1.2 μL L ^?1 SO ₂ . Both sulfite oxidation and sulfite reduction and assimilation contribute to SO ₂ detoxification.

Abstract

In the present study, uptake, susceptibility and metabolism of SO₂ were analyzed in the deciduous tree species poplar (Populus × canescens). A particular focus was on the significance of sulfite oxidase (SO) for sulfite detoxification, as SO has been characterized as a safety valve for SO₂ detoxification in herbaceous plants. For this purpose, poplar plants were exposed to different levels of SO₂ (0.65, 0.8, 1.0, 1.2 μL L^?1) and were characterized by visible injuries and at the physiological level. Gas exchange parameters (stomatal conductance for water vapor, CO₂ assimilation, SO₂ uptake) of the shoots were compared with metabolite levels (sulfate, thiols) and enzyme activities [SO, adenosine 5′-phosphosulfate reductase (APR)] in expanding leaves (80–90 % expanded). The critical dosage of SO₂ that confers injury to the leaves was 1.2 μL L^?1 SO₂. The observed increase in sulfur containing compounds (sulfate and thiols) in the expanding leaves strongly correlated with total SO₂ uptake of the plant shoot, whereas SO₂ uptake rate was strongly correlated with stomatal conductance for water vapor. Furthermore, exposure to high concentration of SO₂ revealed channeling of sulfite through assimilatory sulfate reduction that contributes in addition to SO-mediated sulfite oxidation to sulfite detoxification in expanding leaves of this woody plant species.     

A new ditopic GdIII complex functionalized with an adamantyl moiety as a versatile building block for the preparation of supramolecular assemblies

A dimeric GdAAZTA-like complex (AAZTA is 6-amino-6-methylperhydro-1,4-diazepinetetraacetic acid) bearing an adamantyl group (Gd₂ L1) able to form strong supramolecular adducts with specific hosts such as β-cyclodextrin (β-CD), poly-β-CD, and human serum albumin (HSA) is reported. The relaxometric properties of Gd₂ L1 were investigated in aqueous solution by measuring the ¹H relaxivity as a function of pH, temperature, and magnetic field strength. The relaxivity of Gd₂ L1 (per Gd atom) at 40 MHz and 298 K is 17.6 mM^?1 s^?1, a value that remains almost constant at higher fields owing to the great compactness and rigidity of the bimetallic chelate, resulting in an ideal value for the rotational correlation time for high-field MRI applications (1.5–3.0 T). The noncovalent interaction of Gd₂ L1 with β-CD, poly-β-CD, and HSA and the relaxometric properties of the resulting host–guest adducts were investigated using ¹H relaxometric methods. Relaxivity enhancements of 29 and 108 % were found for Gd₂ L1–β-CD and Gd₂ L1–poly-β-CD, respectively. Binding of Gd₂ L1 to HSA (K _A = 1.2 × 10⁴ M^?1) results in a remarkable relaxivity of 41.4 mM^?1 s^?1 for the bound form (+248 %). The relaxivity is only limited by the local rotation of the complex within the binding site, which decreases on passing from Gd₂ L1–β-CD to Gd₂ L1–HSA. Finally, the applicability of Gd₂ L1 as tumor-targeting agent through passive accumulation of the HSA-bound adduct was evaluated via acquisition of magnetic resonance images at 1 T of B16-tumor-bearing mice. These experiments indicate a considerable signal enhancement (+160 %) in tumor after 60 min from the injection and a very low hepatic accumulation.     

Biological evaluation of a cytotoxic 2-substituted benzimidazole copper(II) complex: DNA damage,antiproliferation and apoptotic induction activity in human cervical cancer cells

Exploring novel chemotherapeutic agents is a great challenge in cancer medicine. To that end, 2-substituted benzimidazole copper(II) complex, [Cu(BMA)Cl₂]·(CH₃OH) (1) [BMA = N,N′-bis(benzimidazol-2-yl-methyl)amine], was synthesized and its cytotoxicity was characterized. The interaction between complex 1 and calf thymus DNA was detected by spectroscopy methods. The binding constant (K _b = 1.24 × 10⁴ M^?1) and the apparent binding constant (K _app = 6.67 × 10⁶ M^?1) of 1 indicated its moderate DNA affinity. Complex 1 induced single strand breaks of pUC19 plasmid DNA in the presence of H₂O₂ through an oxidative pathway. Cytotoxicity studies proved that complex 1 could inhibit the proliferation of human cervical carcinoma cell line HeLa in both time- and dose-dependent manners. The results of nuclei staining by Hoechst 33342 and alkaline single-cell gel electrophoresis proved that complex 1 caused cellular DNA damage in HeLa cells. Furthermore, treatment of HeLa cells with 1 resulted in S-phase arrest, loss of mitochondrial potential, and up-regulation of caspase-3 and -9 in HeLa cells, suggesting that complex 1 was capable of inducing apoptosis in cancer cells through the intrinsic mitochondrial pathway.     

Stable carbon and nitrogen isotope ratios of Eucalyptus and Acacia species along a seasonal rainfall gradient in Western Australia

Key message

Eucalyptus and Acacia species were surprisingly similar with respect to variations in δ ¹³ C, δ ¹⁵ N. Both genera respond with speciation and associated changes in leaf structure to drought.

Abstract

Stable carbon and nitrogen isotope ratios (δ¹³C and δ¹⁵N) in leaves of eucalypts (Corymbia and Eucalyptus) and Acacia (and some additional Fabaceae) species were investigated together with specific leaf area (SLA), leaf nitrogen (N) and leaf phosphorous (P) concentration along a north–south transect through Western Australia covering winter- and summer-dominated rainfall between 100 and 1,200 mm annually. We investigated 62 eucalypts and 78 woody Fabaceae species, mainly of the genus Acacia. Leaf δ¹³C values of Eucalyptus and Acacia species generally increased linearly with latitude from ?29.5 ± 1.3 ‰ in the summer-dominated rainfall zone (15°S–18°S) to about ?25.7 ± 1.1 ‰ in the winter-dominated rainfall zone (29°S–31°S). δ¹⁵N increased initially with southern latitudes (0.5 ± 1.6 ‰ at 15°S; 5.8 ± 3.3 ‰ at 24–29°S) but decreased again further South (4.6 ± 3.5 ‰ at 31°S). The variation in δ¹³C and δ¹⁵N was probably due to speciation of Eucalyptus and Acacia into very local populations. There were no species that were distributed over the whole sampling area. The variation in leaf traits was larger between species than within species. Average nitrogen concentrations were 11.9 ± 1.05 mg g^?1 in Eucalyptus, and were 18.7 ± 4.1 mg g^?1 in Acacia. Even though the average nitrogen concentration was higher in Acacia than Eucalyptus, δ¹⁵N gave no clear indication for N₂ fixation in Acacia. In a multiple regression, latitude (as a surrogate for rainfall seasonality), mean rainfall, leaf nitrogen concentration, specific leaf area and nitrogen fixation were significant and explained 69 % of the variation of δ¹³C, but only 36 % of the variation of δ¹⁵N. Higher nitrogen and phosphorus concentration could give Acacia an advantage over Eucalyptus in arid regions of undefined rainfall seasonality.     

Purple-leaved Ficus lyrata plants produced by overexpressing a grapevine VvMybA1 gene

Key message

This study established an efficient method of regenerating plants of Ficus lyrata and producing purple-leaved F. lyrata plants through genetic transformation using a VvMybA1 gene of grapevine.

Abstract

Ficus lyrata, a species with unique violin- or guitar-shaped leaves, was regenerated from leaf-derived calli cultured on Murashige and Skoog (MS) basal medium supplemented with 4.5 μM N-phenyl-N’-1, 2, 3-thiadiazol-5-yl urea (TDZ) and 0.5 μM α-naphthalene acetic acid (NAA). Leaf discs were inoculated with Agrobacterium tumefaciens strain EHA 105 harboring a binary vector DEAT that contains the VvMybA1 gene and neomycin phosphotransferase (npt II) gene and subsequently cultured on the established regeneration medium supplemented with 100 mg l^?1 kanamycin. Results showed that 87.5 % of the leaf discs produced kanamycin-resistant callus, and 68.8 % of them produced adventitious shoots. Transgenic plants with three leaf colors including green, green-purple, and purple were produced. Regular and quantitative real-time PCR analyses confirmed the integration of transgenes into the host genome. Semi-quantitative RT-PCR analysis indicated that the VvMybA1 gene was responsible for the purple-colored phenotype. Purple-leaved plants with strong color stability grew vigorously in a greenhouse. This study illustrated the feasibility of using a genetically engineered VvMybA1 gene for drastic modification of leaf color of an important woody ornamental plant.     

Atmospheric nitrogen inputs and losses along an urbanization gradient from Boston to Harvard Forest,MA

Urbanization alters nitrogen (N) cycling, but the spatiotemporal distribution and impact of these alterations on ecosystems are not well-quantified. We measured atmospheric inorganic N inputs and soil leaching losses along an urbanization gradient from Boston, MA to Harvard Forest in Petersham, MA. Atmospheric N inputs at urban sites (12.3 ± 1.5 kg N ha^?1 year^?1) were significantly greater than non-urban (5.7 ± 0.5 kg N ha^?1 year^?1) sites with NH₄ ⁺ (median value of 77 ± 4 %) contributing thrice as much as NO₃ ^?. Proximity to urban core correlated positively with NH₄ ⁺ (R² = 0.57, p = 0.02) and total inorganic N inputs (R² = 0.61, p = 0.01); on-road CO₂ emissions correlated positively with NO ₃ ^? inputs (R² = 0.74, p = 0.003). Inorganic N leaching rates correlated positively with atmospheric N input rates (R² = 0.61, p = 0.01), but did not differ significantly between urban and non-urban sites (p > 0.05). Our empirical measurements of atmospheric N inputs are greater for urban areas and less for rural areas compared to modeled regional estimates of N deposition. Five of the nine sites had NO ₃ ^? leached that came almost entirely from nitrification, indicating that the NO₃ ^? in leachate came from biological processes rather than directly passing through the soil. A significant proportion (17–100 %) of NO ₃ ^? leached from the other four sites came directly from the atmosphere. Surprisingly, the four sites where atmospheric sources made up the largest proportion of leachate NO₃ ^? also had relatively low N leaching rates, suggesting that atmospheric N inputs added to terrestrial ecosystems can move to multiple sinks and losses simultaneously, rather than being lost via leaching only after abiotic and biotic sinks have become saturated. This study improves our understanding of atmospheric N deposition and leaching in urban ecosystems, and highlights the need to incorporate urbanization effects in N deposition models.     

Nitrogen dynamics following field application of biochar in a temperate North American maize-based production system

Background and aims

Biochar additions to tropical soils have been shown to reduce N leaching and increase N use efficiency. No studies exist verifying reduced N leaching in field experiments on temperate agricultural soils or identifying the mechanism for N retention.

Methods

Biochar derived from maize stover was applied to a maize cropping system in central New York State at rates of 0, 1, 3, 12, and 30 t?ha^-1 in 2007. Secondary N fertilizer was added at 100, 90, 70, and 50 % of the recommended rate (108 kg N ha^-1). Nitrogen fertilizer enriched with ¹⁵?N was applied in 2009 to the 0 and 12 t?ha^-1 of biochar at 100 and 50 % secondary N application.

Results

Maize yield and plant N uptake did not change with biochar additions (p?>?0.05; n?=?3). Less N (by 82 %; p?<?0.05) was lost after biochar application through leaching only at 100 %?N fertilization. The reason for an observed 140 % greater retention of applied ¹⁵?N in the topsoil may have been the incorporation of added ¹⁵?N into microbial biomass which increased approximately three-fold which warrants further research. The low leaching of applied fertilizer ¹⁵?N (0.42 % of applied N; p?<?0.05) and comparatively high recovery of applied ¹⁵?N in the soil (39 %) after biochar additions after one cropping season may also indicate greater overall N retention through lower gaseous or erosion N losses with biochar.

Conclusions

Addition of biochar to fertile soil in a temperate climate did not improve crop growth or N use efficiency, but increased retention of fertilizer N in the topsoil.     

Effects of exogenous l-arginine on in vitro rooting, chlorophyll, carbohydrate, and proline concentrations in the sweet cherry rootstock M × M 14 (Prunus avium L. × Prunus mahaleb L.)

The effects of indole-3-butyric acid (IBA) alone and in combination with l-arginine on the morphogenic and biochemical responses in shoot tip explants of the cherry rootstock M × M 14 (Prunus avium × Prunus mahaleb) were examined. The maximum root number per rooted explant (16), root fresh (FW) and dry (DW) weights, as well as the rooting percentage (100 %) were recorded when 2 mg l^?1 IBA (alone) were applied. Including the lowest IBA concentration (0.5 mg l^?1) with the lowest and highest l-arginine concentrations (0.5 and 2 mg l^?1, respectively) resulted in the greatest root length. The maximum leaf chlorophyll concentration and shoot length of the initial explant were recorded when 0.5 mg l^?1 IBA plus 2 mg l^?1 l-arginine were applied. In addition, l-arginine in combination with IBA (1 and 2 mg l^?1) was found to suppress shoot FW and DW. On the other hand, l-arginine enhanced the promoting effect of IBA on both root length and leaf chlorophyll concentration. The carbohydrate and proline concentrations in leaves were not significantly altered with the application of IBA alone or in combination with l-arginine. On the other hand, the carbohydrate and proline concentrations in roots were decreased with the application of 1 and 2 mg l^?1 IBA with l-arginine, resulting in the suppression of the promoting effects of IBA. It is clear from the findings that l-arginine has a direct effect on the in vitro rooting of M × M 14 explants, is involved in the function of the photosythetic apparatus, influences leaf chlorophyll content, participates in carbohydrate biosynthesis and metabolism, and is involved in proline accumulation both in leaves and roots.     

Trypanocidal and cytotoxic evaluation of synthesized thiosemicarbazones as potential drug leads against sleeping sickness

Thiosemicarbazones have become one of the promising compounds as new clinical candidates due to their wide spectrum of pharmaceutical activities. The wide range of their biological activities depends generally on their related aldehyde or ketone groups. Here, we report the pharmacological activities of some thiosemicarbazones synthesized in this work. Benzophenone and derivatives were used with N(4)-phenyl-3-thiosemicarbazide to synthesize corresponding five thiosemicarbazones (1–5). Their structures were characterized by spectrometrical methods analysis IR, NMR ¹H & ¹³C and MS. The compounds were then screened in vitro for their antiparasitic activity and toxicity on Trypanosoma brucei brucei and Artemia salina Leach respectively. The selectivity index of each compound was also determined. Four thiosemicarbazones such as 4, 2, 3 and 1 reveal interesting trypanocidal activities with their half inhibitory concentration (IC₅₀) equal to 2.76, 2.83, 3.86 and 8.48 μM respectively, while compound 5 (IC₅₀ = 12.16 μM) showed a moderate anti-trypanosomal activity on parasite. In toxicity test, except compound 1, which showed a half lethal concentration LC₅₀ >281 μM, the others exerted toxic effect on larvae with LC₅₀ of 5.56, 13.62, 14.55 and 42.50 μM respectively for thiosemicarbazones 4, 5, 3 and 2. In agreement to their selectivity index, which is greater than 1 (SI >1), these compounds clearly displayed significant selective pharmaceutical activities on the parasite tested. The thiosemicarbazones 2–5 that displayed significant anti-trypanosomal and cytoxicity activities are suggested to have anti-neoplastic and anti-cancer activities.     

Growth,physiological, biochemical and ionic responses of pistachio seedlings to mild and high salinity

Key message

Depending on salt concentrations, different mechanisms are involved in the tolerance of pistachio and an acclimation to salinity conditions occurs in the leaves that develop in the presence of salt.

Abstract

Pistachio (Pistacia vera L.) is a salt tolerant species that is considered an alternative crop for cultivation in salinzied orchard soils. In this work, 12-week-old pistachio seedlings cultivated in soil under greenhouse conditions were treated with five levels of salinity including control (0.63 dSm^?1), low (2 and 4 dSm^?1) and high (8 and 10 dSm^?1) salt concentrations for further 12 weeks. Plant growth parameters were not affected by mild salinity; a significant reduction was only observed from 8 dSm^?1. Considerable differences were observed between the young and mature leaves regarding osmotic and ionic stress effects of salt. Main compatible solutes were proline in mature leaves, proline and soluble sugars in young leaves, and soluble sugars and amino acids, other than proline, in roots. Concentration and content of Na in the leaves were not significantly increased at low levels of salinity and the K:Na and Ca:Na ratio of leaves were affected only by higher salt concentrations. Using the sequential extraction procedure for cell wall isolation, we observed that both absolute and relative amounts of Na in the cell wall fraction increased under low salinity, while decreased under higher levels of salt supply. Stable water relations, photochemistry and CO₂ assimilation rates particularly of young leaves, as well as ion homeostasis were mechanisms for maintenance of plants growth under mild salinity. Under severe saline conditions, the impaired ability of mature leaves for synthesis of assimilates, preferent allocation of carbohydrates to roots for maintenance of osmotic homeostasis and finally, reduction of protein synthesis caused growth inhibition in pistachio.     

4-[18F]Fluoro-N-methyl-N-(propyl-2-yn-1-yl)benzenesulfonamide ([18F]F-SA): a versatile building block for labeling of peptides, proteins and oligonucleotides with fluorine-18 via Cu(I)-mediated click chemistry

Cu(I)-mediated [3+2]cycloaddition between azides and alkynes has evolved into a valuable bioconjugation tool in radiopharmaceutical chemistry. We have developed a simple, convenient and reliable radiosynthesis of 4-[¹⁸F]fluoro-N-methyl-N-(propyl-2-yn-1-yl)benzenesulfonamide ([ ¹⁸ F]F-SA) as a novel aromatic sulfonamide-based click chemistry building block. [ ¹⁸ F]F-SA could be prepared in a remotely controlled synthesis unit in 32 ± 5 % decay-corrected radiochemical yield in a total synthesis time of 80 min. The determined lipophilicity of [ ¹⁸ F]F-SA (logP = 1.7) allows handling of the radiotracer in aqueous solutions. The versatility of [ ¹⁸ F]F-SA as click chemistry building block was demonstrated by the labeling of a model peptide (phosphopeptide), protein (HSA), and oligonucleotide (L-RNA). The obtained radiochemical yields were 77 % (phosphopeptide), 55–60 % (HSA), and 25 % (L-RNA), respectively. Despite the recent emergence of a multitude of highly innovative novel bioconjugation methods for ¹⁸F labeling of biopolymers, Cu(I)-mediated click chemistry with [ ¹⁸ F]F-SA represents a reliable, robust and efficient radiolabeling technique for peptides, proteins, and oligonucleotides with the short-lived positron emitter ¹⁸F.     

Molecular characterization and primary functional analysis of PeVDE, a violaxanthin de-epoxidase gene from bamboo (Phyllostachys edulis)

Key message

PeVDE was expressed primarily in bamboo leaves, which was up-regulated under high light. The protein encoded by PeVDE had enzyme activity of catalyzing violaxanthin (V) to zeaxanthin (Z) through antheraxanthin (A) as assay shown in vitro.

Abstract

Violaxanthin de-epoxidase (VDE), a key enzyme of xanthophyll cycle, catalyzes conversion from violaxanthin (V) to zeaxanthin (Z) through antheraxanthin (A) to protect photosynthesis apparatus. A cDNA, PeVDE, encoding a VDE was isolated from bamboo (Phyllostachys edulis) by RT-PCR and RACE methods. PeVDE is 1,723 bp and contains an ORF encoding 451 amino acids, with a transit peptide of 103 amino acids. The mature protein is deduced to have 348 amino acids with a calculated molecular weight of 39.6 kDa and a theoretic isoelectric point of 4.5. Semi-quantitative RT-PCR assay indicated that the highest expression level of PeVDE was in leaf, which agreed with the accumulation pattern of PeVDE protein. Real time PCR results showed that PeVDE was up-regulated and reached the highest level after the treatment (1,200 μmo1 m^?2 s^?1) for 2 h, then decreased and kept at the level similar to that of 0.5 h after treatment for 8 h. To investigate the function of PeVDE, mature protein was heterologously expressed in Escherichia coli and the enzymatic activity assay was carried out using V as substrate. The pigments that formed in the reaction mixture were extracted and analyzed by HPLC method. Besides V, A and Z were detected in the reaction mixture, which indicated that the recombinant protein exhibited enzymatic activity of catalyzing V into Z through A. This study indicates that PeVDE functions through regulating the components of xanthophyll cycle, which might be one of the critical factors that contribute to the growth of bamboo under naturally varying light conditions.     

Novel Macrocyclic Monoterpene Glycosides from Bioactive Extract of Parkinsonia aculeata L

Five novel macrocyclic monoterpene O-glycosides, parkinsenes A–E (1–5), and eleven known phenolic metabolites including three 3-O-glycosylflavonols (6–8), five C-glycosylflavones (9–13), p-hydroxybenzoic acid (14), esculetin (15), and diosmetin (16) were isolated from the leaves and small twigs of Parkinsonia aculeata L. (Fabaceae). Their structures were established by chemical and spectroscopic analyses (UV, ESI–MS, and 1D/2D NMR). The investigated 80 % aqueous methanol extract (AME) showed significant analgesic, antipyretic, anti-inflammatory, hepatoprotective, hypoglycemic, hypocholesterolemic, and antioxidant activities in a dose-dependent manner using two different doses 250 and 500 mg/kg b. wt.     

A multi-environmental study of recent breeding progress on nitrogen use efficiency in wheat (Triticum aestivum L.)

Key message

By comparing 195 varieties in eight trials, this study assesses nitrogen use efficiency improvement in high and low nitrogen conditions in European winter wheat over the last 25 years.

Abstract

In a context where European agriculture practices have to deal with environmental concerns and nitrogen (N) fertiliser cost, nitrogen use efficiency (NUE) has to be improved. This study assessed genetic progress in winter wheat (Triticum aestivum L.) NUE. Two hundred and twenty-five European elite varieties were tested in four environments under two levels of N. Global genetic progress was assessed on additive genetic values and on genotype × N interaction, covering 25 years of European breeding. To avoid sampling bias, quality, precocity and plant height were added as covariates in the analyses when needed. Genotype × environment interactions were highly significant for all the traits studied to such an extent that no additive genetic effect was detected on N uptake. Genotype × N interactions were significant for yield, grain protein content (GPC), N concentration in straw, N utilisation, and NUE. Grain yield improvement (+0.45 % year^?1) was independent of the N treatment. GPC was stable, thus grain nitrogen yield was improved (+0.39 % year^?1). Genetic progress on N harvest index (+0.12 % year^?1) and on N concentration in straw (?0.52 % year^?1) possibly revealed improvement in N remobilisation. There has been an improvement of NUE additive genetic value (+0.33 % year^?1) linked to better N utilisation (+0.20 % year^?1). Improved yield stability was detected as a significant improvement of NUE in low compared to high N conditions. The application of these results to breeding programs is discussed.     

Assessment of nitrate leaching loss on a yield-scaled basis from maize and wheat cropping systems

Background and aims

It is so far a gap in knowledge to assess nitrate (NO₃ ^?) leaching loss linking with crop yield for a given cereal cropping system.

Methods

We conducted a meta-analysis on 32 published studies reporting both NO₃ ^? leaching losses and crop yields in the maize (N?=?20) and wheat (N?=?12) systems.

Results

On average, 22 % and 15 % of applied fertilizer N to wheat and maize systems worldwide are leached in the form of NO₃ ^?, respectively. The average area-scaled NO₃ ^- leaching loss for maize (57.4 kg N ha^?1) was approx. two times higher than for wheat (29.0 kg N ha^?1). While, if scaled to crop yields, the average yield-scaled NO₃ ^? losses were comparable between maize (5.40 kg N Mg^?1) and wheat (5.41 kg N Mg^?1) systems. Across all sites, the lowest yield-scaled NO₃ ^? leaching losses were observed at slightly suboptimal fertilization rates, corresponding to 90 % and 96 % of maximum maize or wheat yields, respectively.

Conclusions

Our findings suggest that small adjustments of agricultural N management practices can effectively reduce yield-scaled NO₃ ^? leaching losses. However, further targeted field experiments are still needed to identify at regional scale best agricultural management practices for reducing yield-scaled NO₃ ^? leaching losses in maize and wheat systems.     

Albino midrib 1, encoding a putative potassium efflux antiporter,affects chloroplast development and drought tolerance in rice

Key message

Mutation of the AM1 gene causes an albino midrib phenotype and enhances tolerance to drought in rice

Abstract

K⁺ efflux antiporter (KEA) genes encode putative potassium efflux antiporters that are mainly located in plastid-containing organisms, ranging from lower green algae to higher flowering plants. However, little genetic evidence has been provided on the functions of KEA in chloroplast development. In this study, we isolated a rice mutant, albino midrib 1 (am1), with green- and white-variegation in the first few leaves, and albino midrib phenotype in older tissues. We found that AM1 encoded a putative KEA in chloroplast. AM1 was highly expressed in leaves, while lowly in roots. Chloroplast gene expression and proteins accumulation were affected during chlorophyll biosynthesis and photosynthesis in am1 mutants. Interestingly, AM1 was induced by salt and PEG, and am1 showed enhanced sensitivity to salinity in seed germination and increased tolerance to drought. Taken together, we concluded that KEAs were involved in chloroplast development and played important roles in drought tolerance.     

Design,synthesis, and in vitro evaluation of a binary targeting MRI contrast agent for imaging tumor cells

A binary targeting vector that consists of peptide sequences of Arg-Gly-Asp (RGD) and Asn-Gly-Arg (NGR) motifs has been designed and synthesized using solid-phase peptide synthesis procedure. The vector is then coupled with Gd-DOTA to work as a targeting contrast agent (CA1) for magnetic resonance imaging of human lung adenocarcinoma cells A549. Its longitudinal relaxivity is measured to be 7.55 mM^?1 s^?1 in aqueous solution at a magnetic field of 11.7 T, which is higher than that of Magnevist (4.25 mM^?1 s^?1) in the same conditions. The cell experiment shows, at the same concentration, uptake quantity of CA1 by A549 is much more than Magnevist and also superior over CA2 (a single targeting contrast agent contains only RGD). The uptake can be blocked by the targetable peptide containing RGD or NGR without coupling Gd. To summarize, CA1 has very good ability to target A549 and higher relaxivity than that of Magnevist. So CA1 is promising MRI contrast agent for high-resolution MR molecular imaging of human lung adenocarcinoma A549 cells.