Abscisic acid (ABA) plays an important role in mediating some biotic and abiotic stresses. In the present study, to better understand the relationship of ABA production and Aluminum (Al)-resistance in plants, Al-resistance genotype (Jiyu70) of soybean was adopted to investigate the accumulation and transport of ABA in plants exposed to Al. Results showed that exogenous application of ABA and ABA synthesis inhibitor-fluridone respectively increased and reduced endogenous ABA content in root apices of soybean, and results in the corresponding reduction and aggravation of Al toxicity. Increasing of either Al concentration (0-50 μM) or treatment duration (0-12 h, 30 μM Al) cause a higher inhibition of root elongation and ABA accumulation in root apices of soybean. Al-induced enhancement of endogenous ABA production not only was in roots but also in leaves, whereas La 3+ (behaves similarly as Al 3+ at the level of cell surface) only increased ABA accumulation in roots. In split-root experiments, Al treatment in two parts of roots (Part A, + Al; Part B, + Al) both decreased root elongation and increased ABA accumulation in root apices of soybean. Whereas when only part A of roots was exposed to Al (Part A, + Al; Part B, -Al), endogenous ABA content in root apices increased in part A but inversely in part B, but root elongation inhibition only was found in part A. Using [ 3 H]-ABA radioisotope technique, it was found that [ 3 H]-ABA can transport at the rate of more than 3.2 cm·min −1 in the whole plants, and this can be accelerated by Al supply. In addition, [ 3 H]-ABA tended to distribute in the root part under Al stress. Together, these results suggest that ABA may play an important role in regulating Al resistance of soybean as an Al-stress signal.

The barley (Hordeum vulgare) gene HvALMT1 encodes an anion channel in guard cells and in certain root tissues indicating that it may perform multiple roles. The protein localizes to the plasma membrane and facilitates malate efflux from cells when constitutively expressed in barley plants and Xenopus oocytes. This study investigated the function of HvALMT1 further by identifying its tissue-specific expression and by generating and characterizing RNAi lines with reduced HvALMT1 expression. We show that transgenic plants with 18-30% of wild-type HvALMT1 expression had impaired guard cell function. They maintained higher stomatal conductance in low light intensity and lost water more rapidly from excised leaves than the null segregant control plants. Tissue-specific expression of HvALMT1 was investigated in developing grain and during germination using transgenic barley lines expressing the green fluorescent protein (GFP) with the HvALMT1 promoter. We found that HvALMT1 is expressed in the nucellar projection, the aleurone layer and the scutellum of developing barley grain. Malate release measured from isolated aleurone layers prepared from imbibed grain was significantly lower in the RNAi barley plants compared with control plants. These data provide molecular and physiological evidence that HvALMT1 functions in guard cells, in grain development and during germination. We propose that HvALMT1 releases malate and perhaps other anions from guard cells to promote stomatal closure. The likely roles of HvALMT1 during seed development and grain germination are also discussed.

The concentration of soluble aluminium (Al) in the soil solution increases at low pH and the prevalence of toxic Al3+ cations represent the main factor limiting plant growth on acid soils. Citrate secretion from roots is an important Al-tolerance mechanism in many species including soybean. We isolated mitochondria from the roots of an Al-resistant soybean (Glycine max L.) cv. Jiyu 70 to investigate the relationship between citrate metabolism and Al-induced citrate secretion. Spectrophotometric assays revealed that the activities of mitochondrial malate dehydrogenase and citrate synthase increased and aconitase decreased with increasing of Al concentration (0–50 µM) and duration of Al treatment (30 µM Al, 0.5–9 h). Al-induced citrate secretion was inhibited by the citrate synthase inhibitor suramin, and enhanced by the aconitase inhibitor fluorocitric acid. Mersalyl acid, an inhibitor of a citrate carrier located in mitochondria membrane, also suppressed Al-induced citrate secretion. Transcript level of the mitochondrial citrate synthase gene increased in soybean roots exposed to Al, whereas expression of aconitase showed no significant difference. Expression of Gm-AlCT, a gene showing homology to Al-activated citrate transporters was also induced after 4 h in Al treatment. The Al-dependent changes in activity and expression of these enzymes are consistent with them supporting the sustained release of citrate from soybean roots.

The mechanisms of aluminum (Al) resistance in wheat and rye involve the release of citrate and malate anions from the root apices. Many of the genes controlling these processes have been identified and their responses to Al treatment described in detail. This study investigated how the major Al resistance traits of wheat and rye are transferred to triticale (x Tritosecale Wittmack) which is a hybrid between wheat and rye. We generated octoploid and hexaploid triticale lines and compared them with the parental lines for their relative resistance to Al, organic anion efflux and expression of some of the genes encoding the transporters involved. We report that the strong Al resistance of rye was incompletely transferred to octoploid and hexaploid triticale. The wheat and rye parents contributed to the Al-resistance of octoploid triticale but the phenotypes were not additive. The Al resistance genes of hexaploid wheat, TaALMT1, and TaMATE1B, were more successfully expressed in octoploid triticale than the Al resistance genes in rye tested, ScALMT1 and ScFRDL2. This study demonstrates that an important stress-tolerance trait derived from hexaploid wheat was expressed in octoploid triticale. Since most commercial triticale lines are largely hexaploid types it would be beneficial to develop techniques to generate genetically-stable octoploid triticale material. This would enable other useful traits that are present in hexaploid but not tetraploid wheat, to be transferred to triticale.

Although various radiolabeled tryptophan analogs have been developed to monitor tryptophan metabolism using positron emission tomography (PET) for various human diseases including melanoma and other cancers, their application can be limited due to the complicated synthesis process. In this study, we demonstrated that photoredox radiofluorination represents a simple method to access novel tryptophan-based PET agents. In brief, 4-F-5-OMe-tryptophans (L/D-T13) and 6-F-5-OMe-tryptophans (L/D-T18) were easily synthesized. The 18 F-labeled analogs were produced by photoredox radiofluorination with radiochemical yields ranging from 2.6 ± 0.5% to 32.4 ± 4.1% (3 ≤ n ≤ 5, enantiomeric excess ≥ 99.0%) and over 98.0% radiochemical purity. Small animal imaging showed that L-[ 18 F]T13 achieved 9.58 ± 0.26%ID/g tumor uptake and good contrast in B16F10 tumor-bearing mice (n = 3). Clearly, L-[ 18 F]T13 exhibited prominent tumor uptake, warranting future evaluations of its potential usage in precise immunotherapy monitoring.

We examined the function of OsALMT4 in rice (Oryza sativa L.) which is a member of the aluminum-activated malate transporter family. Previous studies showed that OsALMT4 localizes to the plasma membrane and that expression in transgenic rice lines results in a constitutive release of malate from the roots. Here, we show that OsALMT4 is expressed widely in roots, shoots, flowers, and grain but not guard cells. Expression was also affected by ionic and osmotic stress, light and to the hormones ABA, IAA, and salicylic acid. Malate efflux from the transgenic plants over-expressing OsALMT4 was inhibited by niflumate and salicylic acid. Growth of transgenic lines with either increased OsALMT4 expression or reduced expression was measured in different environments. Light intensity caused significant differences in growth between the transgenic lines and controls. When day-time light was reduced from 700 to 300 μmol m-2s-1 independent transgenic lines with either increased or decreased OsALMT4 expression accumulated less biomass compared to their null controls. This response was not associated with differences in photosynthetic capacity, stomatal conductance or sugar concentrations in tissues. We propose that by disrupting malate fluxes across the plasma membrane carbon partitioning and perhaps signaling are affected which compromises growth under low light. We conclude that OsALMT4 is expressed widely in rice and facilitates malate efflux from different cell types. Altering OsALMT4 expression compromises growth in low-light environments.

Abstract:In contast to the general [4+2] cycloaddition reactions of alkynylcyclopropane ketones reported in the literature, we report herein a Sc(OTf ) 3 -catalyzed formal intermolecular [3+2] cycloaddition reaction of alkynylcyclopropane ketones with electron-rich aromatic aldehydes. 2,3,3,5-Tetrasubstituted tetrahydrofurans were obtained by this method, and the tetrahydrofuran skeleton was diastereoselectively constructed with

Radiolabeled prostate-specific membrane antigen (PSMA) ligands have been rapidly adopted as part of patient care for prostate cancer. In this study, a new series of 18F-labeled PSMA-targeting agents was developed based on the high-affinity Glu-ureido-Lys scaffold and 18F-vinyl sulfones (VSs), the tumor uptake and tumor/major organ contrast of which could be tuned by pharmacokinetic linkers within the molecules. In particular, 18F-PEG3-VS-PSMAi showed the highest tumor uptake (12.1 ± 2.2%ID/g at 0.5 h p.i.) and 18F-PEG2-VS-PSMAi showed the highest tumor-to-liver ratio (T/L = 3.7 ± 1.0, 4.8 ± 1.2, and 6.3 ± 1.1 at 0.5, 1.5, and 3 h p.i. respectively). Significantly, compared with the FDA-approved 68Ga-PSMA-11, the newly developed 18F-PEG3-VS-PSMAi has an almost double tumor uptake (P < 0.0001) when tested in the same animal model. In conclusion, 18F-VS-labeled PSMA ligands are promising PET agents with prominent tumor uptake and high contrast. The lead agents 18F-PEG2-VS-PSMAi and 18F-PEG3-VS-PSMAi warrant further evaluation in prostate cancer patients.