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The ligands BDA (2,2'-bipyridyl-6,6'-dicarboxylic acid) and PDA (1,10-phenanthroline-2,9-dicarboxylic acid) are of interest as functional group types for ion-exchange materials for extracting uranium from the oceans, reported in a previous paper for PDA Lashley, M. A. (

The WHIRLY (WHY) DNA/RNA binding proteins fulfil multiple but poorly characterised functions in leaf development. Here, we show that WHY1 transcript levels were highest in the bases of 7-day old barley leaves. Immunogold labelling revealed that the WHY1 protein was more abundant in the nuclei than the proplastids of the leaf bases. To identify transcripts associated with leaf development we conducted hierarchical clustering of differentially abundant transcripts along the developmental gradient of wild-type leaves. Similarly, metabolite profiling was employed to identify metabolites exhibiting a developmental gradient. A comparative analysis of transcripts and metabolites in barley lines (W1–1 and W1–7) lacking WHY1, which show delayed greening compared with the wild type revealed that the transcript profile of leaf development was largely unchanged in W1–1 and W1–7 leaves. However, there were differences in levels of several transcripts encoding transcription factors associated with chloroplast development. These include a barley homologue of the Arabidopsis GATA transcription factor that regulates stomatal development, greening and chloroplast development, NAC1; two transcripts with similarity to Arabidopsis GLK1 and two transcripts encoding ARF transcriptions factors with functions in leaf morphogenesis and development. Chloroplast proteins were less abundant in the W1–1 and W1–7 leaves than the wild type. The levels of tricarboxylic acid cycle metabolites and GABA were significantly lower in WHY1 knockdown leaves than the wild type. This study provides evidence that WHY1 is localised in the nuclei of leaf bases, contributing the regulation of nuclear-encoded transcripts that regulate chloroplast development.

The formation constants (log

The metal-ion-complexing properties of the tetradentate ligand 2,2'-bi-1,10-phenanthroline (BIPHEN) in 50% CH3OH/H2O are reported for a variety of metal ions. BIPHEN (with two reinforcing benzo groups in the backbone) was compared to other tetrapyridyls, 2,9-di(pyrid-2-yl)-1,10-phenanthroline (DPP; with one benzo group) and 2,2':6',2″:6″,2‴- quaterpyridine (QPY; with no benzo groups), with levels of preorganization BIPHEN > DPP > QPY. Formation constants were determined by following the variation of the intense π → π* transitions in the absorbance spectra of BIPHEN in the presence of metal ion as a function of the pH. The log K1 values show that the increased level of preorganization produced by the two benzo groups, reinforcing the backbone of the BIPHEN ligand, leads to increased complex stability with large metal ions (an ionic radius greater than 0.9 A) compared to the less preorganized tetrapyridines DPP and QPY. In particular, the large CdII ion [log K1(BIPHEN) = 12.7] shows unusual selectivity over the small ZnII ion [log K1(BIPHEN) = 7.78]. The order of levels of preorganization BIPHEN > DPP > QPY leads to enhanced selectivity for SmIII over GdIII with increased preorganization, which is of interest in relation to separating AmIII from GdIII in the treatment of radioactive waste. AmIII is very close in ionic radius to SmIII, so that the size-based selectivity produced by the enhanced preorganization of BIPHEN should translate into enhanced AmIII/GdIII selectivity. The chelation-enhanced fluorescence (CHEF) effect in BIPHEN complexes is discussed. The CHEF effect in the ZnII complex is somewhat smaller than that for CdII, which is discussed in terms of decreased overlap in the Zn-N bonds formed by the too small ZnII, leading to a partial photoinduced-electron-transfer quenching of fluorescence. The structure of the complex [Cd(BIPHEN)2](ClO4)2 is reported and shows that the Cd-N bonds are largely normal for the unusual 8-coordination observed, except that steric clashes between the terminal pyridyl groups of each of the BIPHEN ligands, and the rest of the orthogonal BIPHEN ligand, lead to some stretching of the outer Cd-N bonds.

Funding: This work was funded by the Scottish Government Rural and Environment Science and Analytical Services Division as part of the Strategic Research Programme 2016‐2022, by a GCRF Foundation Awards for Global Agricultural and Food Systems Research funded by the BBSRC project BB/P022553/1 (Quickgro) and EPSRC Reference: EP/T01525X/1, GCRF Global Research Translation Awards, Food Security and Health for East Africa, 2019‐2021, and the European Union’s Horizon 2020 research and innovation programme ADAPT (Accelerated Development of Multiple‐Stress Tolerant Potato), grant agreement No GA 2020 862‐858 and G2P‐SOL (Linking genetic resources, genomes and phenotypes of Solanaceous crops) grant agreement No 677379. Previously, we developed and applied a glasshouse screen for potato tuber yield under heat stress and identified a candidate gene (HSc70) for heat tolerance by genetic analysis of a diploid potato population. Specific allelic variants were expressed at high levels on exposure to moderately elevated temperature due to variations in gene promoter sequence. In this study, we aimed to confirm the results from the glasshouse screen in field trials conducted over several seasons and locations including those in Kenya, Malawi and the UK. We extend our understanding of the HSc70 gene and demonstrate that expression level of HSc70 correlates with tolerance to heat stress in a wide range of wild potato relatives. The physiological basis of the protective effect of HSc70 was explored and we show that genotypes carrying the highly expressed HSc70 A2 allele are protected against photooxidative damage to PSII induced by abiotic stresses. Overall, we show the potential of HSc70 alleles for breeding resilient potato genotypes for multiple environments. Publisher PDF

The influence of genotype and domestic processing on iron and zinc bioavailability in common bean germplasm was investigated using an in vitro digestion model. Raw beans exhibited diversity in iron content (50 to90 mg kg

Tartaric acid has high economic value as an antioxidant and flavorant in food and wine industries. l-Tartaric acid biosynthesis in wine grape (Vitis vinifera) uses ascorbic acid (vitamin C) as precursor, representing an unusual metabolic fate for ascorbic acid degradation. Reduction of the ascorbate breakdown product 2-keto-l-gulonic acid to l-idonic acid constitutes a critical step in this l-tartaric acid biosynthetic pathway. However, the underlying enzymatic mechanisms remain obscure. Here, we identified a V. vinifera aldo-keto reductase, Vv2KGR, with 2-keto-l-gulonic acid reductase activity. Vv2KGR belongs to the d-isomer–specific 2-hydroxyacid dehydrogenase superfamily and displayed the highest similarity to the hydroxyl pyruvate reductase isoform 2 in Arabidopsis thaliana. Enzymatic analyses revealed that Vv2KGR efficiently reduces 2-keto-l-gulonic acid to l-idonic acid and uses NADPH as preferred coenzyme. Moreover, Vv2KGR exhibited broad substrate specificity toward glyoxylate, pyruvate, and hydroxypyruvate, having the highest catalytic efficiency for glyoxylate. We further determined the X-ray crystal structure of Vv2KGR at 1.58 Å resolution. Comparison of the Vv2KGR structure with those of d-isomer–specific 2-hydroxyacid dehydrogenases from animals and microorganisms revealed several unique structural features of this plant hydroxyl pyruvate reductase. Substrate structural analysis indicated that Vv2KGR uses two modes (A and B) to bind different substrates. 2-Keto-l-gulonic acid displayed the lowest predicted free-energy binding to Vv2KGR among all docked substrates. Hence, we propose that Vv2KGR functions in l-tartaric acid biosynthesis. To the best of our knowledge, this is the first report of a d-isomer–specific 2-hydroxyacid dehydrogenase that reduces 2-keto-l-gulonic acid to l-idonic acid in plants.

Metal ion complexing properties of the ligand QPY (2,2′:6′,2′':6′',2′''-quaterpyridine) are reported in relation to its possible use as a functional group for reagents in the extraction and separation of Ln(III) (lanthanide) ions. QPY is almost totally insoluble in water, but variation of the intense π-π* transitions in the UV spectrum of 1 × 10–5 M QPY solutions in 50% CH3OH/H2O (v/v) as a function of pH or metal ion concentration allowed for the determination of the protonation constant (pK) and log K1 values with metal ions. The pKa values of QPY are 4.54 ± 0.02 and 3.47 ± 0.02 in 50% CH3OH/H2O. The log K1 values determined by UV–visible spectroscopy for the Ln(III) ions by titration of 1:1 solutions of 1.0 × 10­5 M Ln(III) ion and QPY between pH 2 and 6 were: La(III), 3.79; Pr(III), 4.34; Nd(III) 4.57; Sm(III), 4.78; Gd(III) 4.69; Dy(III), 4.76, Ho(III), 4.94; Er(III), 5.36, Tm(III), 5.84, and Lu(III) 5.54, all at 25 °C and ionic strength zero. The log K1 values for the Ln(III) ions show quite strong increases from La(III) to Lu(III), with a local maximum at Sm(III), and a local minimum at Gd(III). The local maxium at Sm(III) is attributed to this ion being the best-fit size for coordinating with polypyridyl ligands. The effect of preorganization of polypyridyls such as QPY with bridging benzo groups in the ligand backbone to yield DPP (2,9-dipyrid-2-yl-1,10-phenanthroline) is to produce significant increases in log K1 for large metal ions such as Ln(III) ions, but for small metal ions such as Zn(II), there is a large decrease in log K1 in passing from QPY to DPP: this shows how rigidification of the ligand can enhance the selectivity against small metal ions of polypyridyls forming five-membered chelate rings. DFT calculations are used to analyze the variation in log K1 in passing from the La(III) complexes of QPY to DPP compared to those for the smaller Lu(III) ion.

‘Crumbly’ fruit is a developmental disorder in raspberry that results in malformed and unsaleable fruits. For the first time, we define two distinct crumbly phenotypes as part of this work. A consistent crumbly fruit phenotype affecting the majority of fruits every season, which we refer to as crumbly fruit disorder (CFD) and a second phenotype where symptoms vary across seasons as malformed fruit disorder (MFD). Here, segregation of crumbly fruit of the MFD phenotype was examined in a full-sib family and three QTL (Quantitative Trait Loci) were identified on a high density GbS (Genotype by Sequencing) linkage map. This included a new QTL and more accurate location of two previously identified QTLs. A microarray experiment using normal and crumbly fruit at three different developmental stages identified several genes that were differentially expressed between the crumbly and non-crumbly phenotypes within the three QTL. Analysis of gene function highlighted the importance of processes that compromise ovule fertilization as triggers of crumbly fruit. These candidate genes provided insights regarding the molecular mechanisms involved in the genetic control of crumbly fruit in red raspberry. This study will contribute to new breeding strategies and diagnostics through the selection of molecular markers associated with the crumbly trait.

Potato is a major global crop that has an important role to play in food security, reducing poverty and improving human nutrition. Productivity in potato however is limited in many environments by its sensitivity to abiotic stresses such as elevated temperature, drought, frost, and salinity. In this chapter we focus on the effects of elevated temperature on potato yields as high temperature is the most important uncontrollable factor affecting growth and yield of potato. We describe some of the physiological impacts of elevated temperature and review recent findings about response mechanisms. We describe genetic approaches that could be used to identify allelic variants of genes that may be useful to breed for increased climate resilience, an approach that could be deployed with recent advances in potato breeding.

Background In maritime growing environments, blueberry yield often exhibits excessive season-to-season variation, associated with poorly adapted photosynthetic responses to low light conditions. It is therefore necessary to develop methods that stabilise yield while maintaining or improving fruit quality. Here, we placed reflective mulch alongside plants at the early green fruit stage, to test the hypothesis that increasing the available seasonal light integral could enhance blueberry yield. We further determined several quality characteristics to ensure fruit marketability. Results Placement of mulch alongside plants reflected up to five times more light compared with bare ground, enhancing the amount of light reaching the canopy. This led to an adaptive increase of light saturated maximal photosynthetic rate of mulch-treated plants, resulting in a twofold increase in yield compared with control plants. Analysis of fruit quality characteristics showed that total soluble solids, sugars and organic acids were similar between treatments. Likewise, antioxidant capacity, total anthocyanin content and the content of individual anthocyanins did not change in response to reflective mulch treatment. Conclusions The use of reflective mulch should be explored by industry as a cost-effective method for enhancing blueberry yield while maintaining fruit quality in maritime environments. © 2020 Society of Chemical Industry.

Pine pitch canker (PPC), caused by Fusarium circinatum Nirenberg and O’Donnell, represents an important threat to conifer forests worldwide, being associated with significant economic losses. Although essential to develop disease mitigation strategies, little research focused on host susceptibility/resistance mechanisms has been conducted. We aimed to explore the response of a highly susceptible (Pinus radiata D. Don) and a relatively resistant (Pinus pinea L.) species to F. circinatum infection at different stages of infection. Morpho-physiological, hormonal and oxidative stress-related changes were assessed for each pine species and sampling point. Most of the changes found occurred in symptomatic P. radiata, for which an increased susceptibility to photoinhibition was detected together with decreased superoxide dismutase activity. Abscisic acid catabolism was activated by F. circinatum inoculation in both pine species, leading to the accumulation of the inactive dihydrophaseic acid in P. radiata and of the less-active phaseic acid in P. pinea. Hormone confocal analysis revealed that this strategy may be of particular importance at 6 d.p.i. in P. pinea, which together with photosynthesis maintenance to fuel defense mechanism, could in part explain the species resistance to PPC. These results are of great interest for the development of hormone-based breeding strategies or for the use of hormone application as inducers of resistance to F. circinatum infection.

Potato production is often constrained by abiotic stresses such as drought and high temperatures which are often present in combination. In the present work, we aimed to identify key mechanisms and processes underlying single and combined abiotic stress tolerance by comparative analysis of tolerant and susceptible cultivars. Physiological data indicated that the cultivars Desiree and Unica were stress tolerant while Agria and Russett Burbank were stress susceptible. Abiotic stress caused a greater reduction of photosynthetic carbon assimilation in the susceptible cultivars which was associated with a lower leaf transpiration rate. Oxidative stress, as estimated by the accumulation of malondialdehyde was not induced by stress treatments in any of the genotypes with the exception of drought stress in Russett Burbank. Stress treatment resulted in increases in ascorbate peroxidase activity in all cultivars except Agria which increased catalase activity in response to stress. Transcript profiling highlighted a decrease in the abundance of transcripts encoding proteins associated with PSII light harvesting complex in stress tolerant cultivars. Furthermore, stress tolerant cultivars accumulated fewer transcripts encoding a type-1 metacaspase implicated in programmed cell death. Stress tolerant cultivars exhibited stronger expression of genes associated with plant growth and development, hormone metabolism and primary and secondary metabolism than stress susceptible cultivars. Metabolite profiling revealed accumulation of proline in all genotypes following drought stress that was partially suppressed in combined heat and drought. On the contrary, the sugar alcohols inositol and mannitol were strongly accumulated under heat and combined heat and drought stress while galactinol was most strongly accumulated under drought. Combined heat and drought also resulted in the accumulation of Valine, isoleucine, and lysine in all genotypes. These data indicate that single and multiple abiotic stress tolerance in potato is associated with a maintenance of CO2 assimilation and protection of PSII by a reduction of light harvesting capacity. The data further suggests that stress tolerant cultivars suppress cell death and maintain growth and development via fine tuning of hormone signaling, and primary and secondary metabolism. This study highlights potential targets for the development of stress tolerant potato cultivars.

The formation of complexes of Hg(II) with the tetradentate polypyridyl ligands (L) qpy (2,2′:6′, 2′':6′',2′''-quaterpyridine), DPP (2,9-di-2-pyridinyl-1,10-phenanthroline), biphen (2,2′-bi-1,10-phenanthroline), and ebip (diquino[8,7-b:7′,8′-j][1,10]phenanthroline, 8,9-dihydro­), and the tridentate tpy (2,2′:6′,2′'-​terpyridine) is monitored by absorbance and fluorescence spectroscopy. The pH-dependence studies of fluorescence showed complete quenching of all fluorescence until the spectra of the free non-protonated ligands appeared at pH ≥ 9, attributed to the equilibrium Hg(L)22+ + 2 OH– ⇆Hg(OH)2 + 2 L. The absorbance titrations were carried out between pH 2 and 12 with 10-5 M L and 10-5 M or 5 × 10-6 M Hg(ClO4)2 to give 1:1 or 2:1 L:Hg ratios. These also showed the above hydrolysis of the HgL22+ complexes by hydroxide to give Hg(OH)2 at the higher pH values, but showed other equilibria at lower pH not apparent in the fluorescence titrations. At pH values around 7 a pH dependent equilibrium attributed to formation of the HgL22+ from the HgL2+ complexes was observed: HgL2+ + 2 OH– ⇆Hg(OH)2 + HgL22+. At around pH 2–3 a further equilibrium was observed, assigned to HgL2+ + H+ ⇆HgLH3+. Analysis of all these titrations gave log K1 values with Hg(II) as follows (ionic strength zero, 25 °C): qpy, 18.0; DPP, 18.7; biphen, 20.4; ebip, 21.8, where log β2 values are qpy, 24.0; DPP, 28.0; biphen, 28.6; ebip, 30.8. For the tridentate tpy complexes of Hg(II) log β 2 of 23.3 was obtained, but very little of the HgL2+ complex appeared to be present, with the [Hg(tpy)2]2+ complex plus Hg(OH)2 (aq) dominating. Only an estimate of log K1 ∼ 10.6 for Hg(II)/tpy could be obtained. The effect of increasing preorganization of the ligands along the series qpy

The fluorescence properties of the ligand idpa (1H-Indole-3-ethanamine, N,N-bis(2-pyridinylmethyl)amine) complexed with metal ions along with their crystal structures were investigated to further understand the role of π contacts in quenching fluorescence. In particular, the π contacting ability of indole fluorophore of idpa and its impact on the fluorescence properties are compared to those of anthracene (in adpa) and coumarin fluorophores (in cdpa) investigated previously by us. Unlike adpa and cdpa, the fluorescence of free idpa increases with rising pH, which is attributed via TD-DFT studies to quenching at lower pH values by a proton transfer in the excited state from the protonated tertiary amine to the pydridyl nitrogen. Structural studies show that the AgI complex of idpa is a dimer held together by very short inter-complex η1 Ag···C π contacts of 2.382 A, indicating powerful π contacting ability of indole as expected from the electrostatic potential map. However, structural studies of the ZnII, NiII, PbII, and CdII complexes of idpa show no metal-fluorophore π contacts present in the solid state, which was ascribed to a plethora of other π contacts and hydrogen bondings possible only in solid state. All metal ions on complex-formation cause quenching of fluorescence of idpa relative to that of free idpa at pH 7.45, suggesting the existence of π contacts in solution. DFT/TD-DFT studies showed that O-H···C π contacts with the solvent stabilizes the excited state and makes the S1 → S0 emission to be a charge transfer transition, quenching the fluorescence of ZnIIidpa, and possibly CdIIidpa as well. The existence of π contacts in solution was also reflected in the fact that the ZnII and CdII complexes show increased fluorescence intensity when titrated with Cl−, which could be due to the disruption of fluorescence-quenching O-H···C π contacts with solvent molecules. The observed fluorescence responses of ZnII and CdII complexes to Cl− render these complexes to be used as a possible sensor for Cl−.

A powerful acquired thermotolerance response in potato was demonstrated and characterised in detail, showing the time course required for tolerance, the reversibility of the process and requirement for light. Potato is particularly vulnerable to increased temperature, considered to be the most important uncontrollable factor affecting growth and yield of this globally significant crop. Here, we describe an acquired thermotolerance response in potato, whereby treatment at a mildly elevated temperature primes the plant for more severe heat stress. We define the time course for acquiring thermotolerance and demonstrate that light is essential for the process. In all four commercial tetraploid cultivars that were tested, acquisition of thermotolerance by priming was required for tolerance at elevated temperature. Accessions from several wild-type species and diploid genotypes did not require priming for heat tolerance under the test conditions employed, suggesting that useful variation for this trait exists. Physiological, transcriptomic and metabolomic approaches were employed to elucidate potential mechanisms that underpin the acquisition of heat tolerance. This analysis indicated a role for cell wall modification, auxin and ethylene signalling, and chromatin remodelling in acclimatory priming resulting in reduced metabolic perturbation and delayed stress responses in acclimated plants following transfer to 40 °C.

Senescent sweetening results in the accumulation of reducing sugars in potato tubers following extended periods of storage at moderate temperatures used to avoid the separate condition of cold-induced sweetening. It represents a significant problem for the potato processing industry due to the development of dark fry colour and the accumulation of acrylamide in processed products. Previous studies have implicated oxidative stress in the accumulation of reducing sugars in potato tubers over long term storage. However, in the present analysis we found no evidence for a correlation between oxidative stress as estimated from quantification of hydrogen peroxide, lipid peroxidation or activity of redox enzymes and the accumulation of reducing sugars. On the contrary, transcriptional profiling indicated changes in carbohydrate metabolism were associated with the onset of senescent sweetening and qRT-PCR indicated that reduced abundance of transcripts encoding a plastidial glucose-6-phosphate/phosphate translocator was widely observed during sweetening onset in multiple genotypes. Our data suggest that reduction in the capacity of plastids to import glucose-6-phosphate reduces the capacity for starch resynthesis in the stored tuber thereby shifting the metabolic balance towards starch turnover resulting in reducing sugar accumulation.

The mechanisms underpinning plant perception of phloem-feeding insects, particularly aphids, remain poorly characterized. Therefore, the role of apoplastic redox state in controlling aphid infestation was explored using transgenic tobacco (Nicotiana tabacum) plants that have either high (PAO) or low (TAO) ascorbate oxidase (AO) activities relative to the wild type. Only a small number of leaf transcripts and metabolites were changed in response to genotype, and cell wall composition was largely unaffected. Aphid fecundity was decreased significantly in TAO plants compared with other lines. Leaf sugar levels were increased and maximum extractable AO activities were decreased in response to aphids in all genotypes. Transcripts encoding the Respiratory Burst Oxidase Homolog F, signaling components involved in ethylene and other hormone-mediated pathways, photosynthetic electron transport components, sugar, amino acid, and cell wall metabolism, were increased significantly in the TAO plants in response to aphid perception relative to other lines. The levels of galactosylated xyloglucan were decreased significantly in response to aphid feeding in all the lines, the effect being the least in the TAO plants. Similarly, all lines exhibited increases in tightly bound (1→4)-β-galactan. Taken together, these findings identify AO-dependent mechanisms that limit aphid infestation.

This work was funded by the BBSRC grant (BB/M004899/1) as part of the ERA-CAPS project HotSol and the Scottish Government Rural and Environment Science and Analytical Services Division as part of the Strategic Research Programme 2016-2021 For many commercial potato cultivars, tuber yield is optimal at average daytime temperatures in the range of 14–22 °C. Further rises in ambient temperature can reduce or completely inhibit potato tuber production, with damaging consequences for both producer and consumer. The aim of this study was to use a genetic screen based on a model tuberization assay to identify quantitative trait loci (QTL) associated with enhanced tuber yield. A candidate gene encoding HSc70 was identified within one of the three QTL intervals associated with elevated yield in a Phureja–Tuberosum hybrid diploid potato population (06H1). A particular HSc70 allelic variant was linked to elevated yield in the 06H1 progeny. Expression of this allelic variant was much higher than other alleles, particularly on exposure to moderately elevated temperature. Transient expression of this allele in Nicotiana benthamiana resulted in significantly enhanced tolerance to elevated temperature. An TA repeat element was present in the promoter of this allele, but not in other HSc70 alleles identified in the population. Expression of the HSc70 allelic variant under its native promoter in the potato cultivar Desiree resulted in enhanced HSc70 expression at elevated temperature. This was reflected in greater tolerance to heat stress as determined by improved yield under moderately elevated temperature in a model nodal cutting tuberization system and in plants grown from stem cuttings. Our results identify HSc70 expression level as a significant factor influencing yield stability under moderately elevated temperature and identify specific allelic variants of HSc70 for the induction of thermotolerance via conventional introgression or molecular breeding approaches. Publisher PDF

Commercially, blackcurrants (Ribes nigrum L.) are grown mainly for processing, especially for juice production. They are valued for their high levels of polyphenols, especially anthocyanins, which contribute to their characteristic deep colour, but also as a good source of vitamin C. Recently, evidence has accrued that polyphenols, such as anthocyanins, may have specific human health benefits. The aims of this study were to investigate the genetic control of polyphenols and other key juice processing traits in blackcurrants. The levels, over 2 years, of vitamin C, citrate, malate, succinate, total organic acids, total anthocyanins and total phenolics together with 46 mainly polyphenol metabolites were measured in a blackcurrant biparental mapping population. Quantitative trait loci (QTLs) for these traits were mapped onto a high-density SNP linkage map. At least one QTL was detected for each trait, with good consistency between the 2 years. Clusters of QTLs were found on each of the eight linkage groups (LG). For example, QTLs for the major anthocyanidin glucosides, delphinidin-3-O-glucoside and cyanidin-3-O-glucoside, co-localised with a QTL for total anthocyanin content on LG3 whereas the major anthocyanidin rutinosides, delphinidin-3-O-rutinoside and cyanidin-3-O-rutinoside, had QTLs on LG1 and LG2. Many of the QTLs explained a high proportion of the trait variation, with the most significant region, on LG3 at ~ 35 cM, explaining more than 60% of the variation in the coumaroylated metabolites, Cyanidin-coumaroyl-glucose, Delphinidin-coumaroyl-glucose, Kaempferol-coumaroyl-glucose and Myricetin-coumaroyl-glucose. The identification of robust QTLs for key polyphenol classes and individual polyphenols in blackcurrant provides great potential for marker-assisted breeding for improved levels of key components.

Fusarium circinatum, the causal agent of pine pitch canker (PPC), is an emergent and still understudied risk that threatens Pinus forests worldwide, with potential production and sustainability losses. In order to explore the response of pine species with distinct levels of susceptibility to PPC, we investigated changes in physiology, hormones, specific gene transcripts, and primary metabolism occurring in symptomatic Pinus pinea, Pinus pinaster, and Pinus radiata upon inoculation with F. circinatum. Pinus radiata and P. pinaster exhibiting high and intermediate susceptibility to PPC, respectively, suffered changes in plant water status and photosynthetic impairment. This was associated with sink metabolism induction, a general accumulation of amino acids and overexpression of pathogenesis-related genes. On the other hand, P. pinea exhibited the greatest resistance to PPC and stomatal opening, transpiration increase, and glycerol accumulation were observed in inoculated plants. A stronger induction of pyruvate decarboxylase transcripts and differential hormones regulation were also found for inoculated P. pinea in comparison with the susceptible Pinus species studied. The specific physiological changes reported herein are the first steps to understand the complex Pinus–Fusarium interaction and create tools for the selection of resistant genotypes thus contributing to disease mitigation.

Studies of the complexation of new promising ligands with uranyl (UO22+) and other seawater cations can aid the development of more efficient, selective, and robust sorbents for the recovery of uranium from seawater. In this work, we propose that the ligand design principles based on structural preorganization can be successfully applied to obtain a dramatic enhancement in UO22+ ion binding affinity and selectivity. This concept is exemplified through the investigation of the complexes of UO22+, VO2+, and VO2+ with the highly preorganized ligand 1,10-phenanthroline-2,9-dicarboxylic acid (PDA) using a combination of fluorescence and absorbance techniques, along with density functional theory (DFT) calculations. The measured stability constant value, log K1, of 16.5 for the UO22+/PDA complex is very high compared to uranyl complexes with other dicarboxylic ligands. Moreover, PDA exhibits strong selectivity for uranyl over vanadium ions, since the determined stability constant values of the PDA complexes of ...

The formation constants of the UO22+ cation with the amidoximate ligands bzam (benzamidoxime) and acetam (acetamidoxime) are reported. These are of interest in light of their proposed use as the functional groups of extractants for uranium in seawater. The formation constants of bzam with UO22+ were measured by monitoring the absorbance of the π → π∗ transitions in the UV spectrum of the bzam ligand in the presence of 1:1 UO22+ as a function of pH. This yielded log K1 = 12.4 for UO22+ with bzam, and log K = 6.9 for the equilibrium UO2(bzam)+ + OH− = UO2(bzam)OH at 25 °C and ionic strength zero. The bzam complexes were also studied monitoring the fluorescence of the UO22+ system. Analysis of the intense fluorescence that occurs in 5 × 10−6 M UO22+ solutions between pH 5 and 9 suggested that this was due to the [(UO2)3O(OH)3]+ trimer. Monomeric species such as UO22+ and [UO2(OH)4]2−, and dimers such as [(UO2)(OH)2]2+, fluoresce only weakly. Titration of such solutions with bzam supported the above log K values measured by absorbance, and with higher bzam concentrations yielded log β2 = 22.3. The acetam ligand does not have any absorbance, so that complex-formation was monitored by fluorescence only. Formation constants measured by fluorescence may differ from those measured by other techniques such as absorbance. The agreement obtained between log K values measured by absorbance and fluorescence for the bzam complex of UO22+ supported the log K values measured for the acetam complexes by florescence alone were reliable: log K1 = 13.6, log β2 = 23.7, and log K UO2(acetam)+ + OH− = UO2(acetam)OH = 6.8. The high log K values found for the bzam and acetam complexes of UO22+ were analyzed using DFT calculations. These log K values are related to the ability of polymer-based extractants bearing bzam or acetam type functional groups to extract UO22+ at a concentration of 1.3 × 10−8 M and in the competing 0.0025 M CO32− present in the oceans.

The fluorescence of TB-cyclen (1,4,7,10-tetrabenzyl-1,4,7,10-tetraaza-cyclododecane) and its complexes with CuII, CdII, PbII, ZnII, HgII and AgI are reported in 50% (v/v) CH3OH/H2O. It appears, as supported by NMR studies, that the TB-cyclen undergoes slow protonation reactions in CH3CN with 0.01 M HClO4 present. The non-protonated TB-cyclen adopts the ++−− conformer that is sterically shielded from protonation and complex-formation, and the slow formation of the protonated forms of the ligand, and formation of the ++++ conformer, is required before complex-formation can occur. Strong emissions at 352 nm are oberved on formation of TB-cyclen complexes with CuII, CdII, PbII, but not with ZnII, HgII and AgI: it is suggested that these are exciplex emissions. The selectivity of the fluorescence of CuII with TB-cyclen compared to ZnII suggests that ligands of this type might be useful in sensing CuII in neural tissue, as in the case of studying Alzheimer’s disease, where potentially interefering metal ions such as CdII or PbII should not be present. The structure of [Pb(TB-cyclen)](ClO4)2 is reported, which shows that Pb···C π contacts are formed to all four N-benzyl groups. Structures of [Cd(TB-cyclen)CH3CN](ClO4)2 and [Hg(TB-cyclen)CH3CN](ClO4)2 are reported, that show M···C π contacts to only two of the N-benzyl groups, but the non-formation of four π contacts may be due to the presence of coordinated CH3CN molecules. The structure of [TB-cyclenH]ClO4 shows that the cyclen moeity of the ligand has the ++++ conformer required for complex-formation with metal ions. It is suggested that in the protonated forms of the free ligand, the ++++ conformer is stabilized with the N-benzyl groups in an upright position by the formation of N H···C π contacts, and C H···C π contacts between the upright N-benzyl groups. DFT calculations are carried out that show the structure of the exciplex that can be formed in the free (non-protonated) form of DB-cyclen, and show that its ++−− conformer is the lowest energy form.

In some growing environments blueberry (Vaccimium corymbosum L.) yields exhibit excessive annual variation associated with poor photosynthetic performance. The purpose of this study was to determine how photosynthesis may be affected by demand and to define the mechanisms underpinning photosynthetic plasticity. Manipulation of source-sink ratios revealed that yields were maintained following 50 % defoliation. This was associated with an adaptive increase in photosynthetic capacity mediated via changes in stomatal physiology, photosynthetic electron transport and CO2 assimilation. Transcripts encoding enzymes of the Calvin-Benson cycle including the Rubisco large subunit, Rubisco activase, phosphoribulokinase and plastid-localised glyceraldehyde phosphate dehydrogenase 3 were more abundant in leaves from partially defoliated plants relative to control plants. Short-term 13CO2 labelling experiments suggested that partial defoliation did not incur an assimilation penalty although the accumulation of sugars and starch in some organs was reduced. Metabolite profiles of leaves from partially defoliated plants exhibited some differences from those of control leaves, however, no changes in the diurnal content of leaf sugar and starch were observed between treatments. The data highlights the mechanisms by which blueberry leaves adapt to increased demand and demonstrate that photosynthetic plasticity can compensate for significant loss of the photosynthetic area.

Metal complexing and fluorescence properties of MB-cyclen (1-phenylmethyl-1,4,7,10-tetraazacyclododecane) and its complexes with metal ions in 50% CH3OH/H2O are described. The crystallographic structures of the complexes [(Zn(MB-cyclen))2OH](ClO4)3(2·13H2O), [Ag(MB-cyclen)(ClO4)], [Pb(MB-cyclen)(ClO4)2], [Hg(MB-cyclen)(ClO4)2], [Cu(MB-cyclen)(ClO4)2], and [Ni(MB-cyclen)(ClO4)2] are reported. The normal fluorescence peak of the benzyl group was observed at 289 nm and only the ZnII ion showed a strong CHEF (chelation enhanced fluorescence) effect for the 289 nm peak, which is in line with its lower position in the well-known order of ability to form fluorescence quenching π contacts: ZnII ≪ CdII

Background Phosphorus (P) deficiency limits crop production worldwide. Crops differ in their ability to acquire and utilise the P available. The aim of this study was to determine root traits (root exudates, root system architecture (RSA), tissue-specific allocation of P, and gene expression in roots) that (a) play a role in P-use efficiency and (b) contribute to large shoot zinc (Zn) concentration in Brassica oleracea. Results Two B. oleracea accessions (var. sabellica C6, a kale, and var. italica F103, a broccoli) were grown in a hydroponic system or in a high-throughput-root phenotyping (HTRP) system where they received Low P (0.025 mM) or High P (0.25 mM) supply for 2 weeks. In hydroponics, root and shoot P and Zn concentrations were measured, root exudates were profiled using both Fourier-Transform-Infrared spectroscopy and gas-chromatography-mass spectrometry and previously published RNAseq data from roots was re-examined. In HTRP experiments, RSA (main and lateral root number and lateral root length) was assessed and the tissue-specific distribution of P was determined using micro-particle-induced-X-ray emission. The C6 accession had greater root and shoot biomass than the F103 accession, but the latter had a larger shoot P concentration than the C6 accession, regardless of the P supply in the hydroponic system. The F103 accession had a larger shoot Zn concentration than the C6 accession in the High P treatment. Although the F103 accession had a larger number of lateral roots, which were also longer than in the C6 accession, the C6 accession released a larger quantity and number of polar compounds than the F103 accession. A larger number of P-responsive genes were found in the Low P treatment in roots of the F103 accession than in roots of the C6 accession. Expression of genes linked with “phosphate starvation” was up-regulated, while those linked with iron homeostasis were down-regulated in the Low P treatment. Conclusions The results illustrate large within-species variability in root acclimatory responses to P supply in the composition of root exudates, RSA and gene expression, but not in P distribution in root cross sections, enabling P sufficiency in the two B. oleracea accessions studied.

The ligand DC-18-ane-N2O4 (7,16-bis(6,7-dimethoxy-1-benzopyran-2-one-4-methyl)-1,4,10,13-tetraoxa-7,16-diazacyclooctadecane) is synthesized and its fluorescence responses to the binding of a set of metal ions (Zn2+, Cd2+, Hg2+, Pb2+, Cu2+ and Ag+) are investigated. Among the metal-ligand complexes studied here, the crystal structures of [Ag(DC-18-ane-N2O4)]ClO4·H2O, [Pb(DC-18-ane-N2O4)(ClO4)2H2O] 3·.5H2O and [DC-18-ane-N2O4)H2](ClO4)2.ClCH2CH2Cl are reported. Design of DC-18-ane-N2O4 as a selective turn-on sensor for heavy metal ions is based on two important factors: 1) target metal ions can be selectively complexed according to their sizes, and 2) quenching of fluorescence is related to the ability to form π contacts between the complexed metal ion and the fluorophore of the sensor. The fluorescence study shows that the size of macrocyclic 18-ane-N2O4 is too large for the Zn2+ to bind tightly, but right for Cd2+. This leads to a strong CHEF (Chelation enhanced fluorescence) effect for Cd2+, but not for Zn2+, which renders DC-18-ane-N2O4 a selective Cd2+ sensor over the ubiquitous Zn2+. In fact, it is found that Zn2+ induces fluorescence quenching, which is quite unusual as Zn2+ almost always causes a CHEF effect. For the heavier and larger metal ions tested in this work, the fluorescence intensities are found to be in line with the ability to form π contacts with the fluorophore: Cd2+

Blackcurrant fruit collected at six stages of development were assessed for changes in gene expression using custom whole transcriptome microarrays and for variation in metabolite content using a combination of liquid chromatography-mass spectrometry and gas chromatography-mass spectrometry. Principal components analysis demonstrated that fruit development could be clearly defined according to their transcript or metabolite profiles. During early developmental stages, metabolite profiles were dominated by amino acids and tannins, whilst transcript profiles were enriched in functions associated with cell division, anatomical structure morphogenesis and cell wall metabolism. During mid fruit development, fatty acids accumulated and transcript profiles were consistent with seed and embryo development. At the later stages, sugars and anthocyanins accumulated consistent with transcript profiles that were associated with secondary metabolism. Transcript data also indicated active signaling during later stages of fruit development. A targeted analysis of signaling networks revealed a dynamic activation and repression of almost 60 different transcripts encoding transcription factors across the course of fruit development, many of which have been demonstrated as pivotal to controlling such processes in other species. Transcripts associated with cytokinin and gibberellin were highly abundant at early fruit development, whilst those associated with ABA and ethylene tended to be more abundant at later stages. The data presented here provides an insight into fruit development in blackcurrant and provides a foundation for further work in the elucidation of the genetic basis of fruit quality.

Previous knowledge suggested the involvement of specific pathways/proteins that could be identified as potential molecular indicators linked to enhanced drought tolerance in Eucalyptus globulus. Here, we looked for specific variations in key transcripts of two Eucalyptus globulus clones (AL-18 and AL-13) exposed to water deficit and rehydration with two main goals: (i) to check if and how transcripts potentially associated with stress response and protection are modulated in a controlled experiment; and (ii) to verify if the transcript response is robust in a field case study. Our results showed that the controlled experiment induced a severe acute stress that resulted in a strong realignment of gene expression resulting from an overwhelming of physiological adjustments to water limitation. A number of transcripts exhibited altered abundance after the acute water stress: reduction of RuBisCO activase and mitochondrial glycine cleavage system H protein, and increase of isoflavone reductase. Malate dehydrogenase, catalase, dehydration response element B1A and potassium channel GORK showed a different abundance pattern in each clone. The stress in the field was more moderate and chronic and the plants were able to deal with the stress primarily through physiological adjustments resulting in much smaller changes in gene expression. The transcripts of clone AL-18 showed few alterations between irrigated and non-irrigated plants throughout the experiment, while the transcript changes found in clone AL-13 highlighted the impact of early rewatering rather than growing under extended drought typical of a Mediterranean summer. Although a few concurrent responses were found, the results obtained in the field study draw a very distinct picture when compared with the controlled experiment.

Photosynthetic limitation under a northern European environment precludes carbon storage and drives fruit abortion in blueberries causing yield instability. This highlights the need to develop cultivars adapted to maritime environments., Published evidence indicates that nearly 60% of blueberry-producing countries experience yield instability. Yield is a complex trait determined by genetic and environmental factors. Here, using physiological and biochemical approaches, we tested the hypothesis that yield instability results from year-to-year environmental variation that limits carbon assimilation, storage and partitioning. The data indicate that fruit development depends primarily on the daily production of non-structural carbohydrates by leaves, and there is no accumulation of a starch buffer to allow continuous ripening under conditions limiting for photosynthesis. Photosynthesis was saturated at moderate light irradiance and this was mainly due to stomatal and biochemical limitations. In a dynamic light environment, photosynthesis was further limited by slow stomatal response to increasing light. Finally, labelling with 13CO2 at specific stages of fruit development revealed a relatively even distribution of newly assimilated carbon between stems, roots and fruits, suggesting that the fruit is not a strong sink. We conclude that a significant component of yield variability results from limitations in photosynthetic efficiency that are compounded by an inability to accumulate starch reserves in blueberry storage tissues in a typical northern European environment. This work informs techniques for improving agronomic management and indicates key traits required for yield stability in such environments.

The π-contact hypothesis, that quenching of the fluorescence of complexes of photoinduced electron transfer sensors with heavy diamagnetic metal ions may be caused by π contacts between the metal ion and the fluorophore of the sensor, is examined with a study of the fluorescent properties of the sensor 4-[[bis(2-pyridinylmethyl)amino]methyl]-6,7-dimethoxy-1-benzopyran-2-one (cdpa) and the structures of its complexes with some metal ions. The coumarin-type fluorophore of cdpa is a weaker π-contact former than the anthracenyl fluorophore of the analogue adpa (Inorg. Chem. 2014, 53, 9014): only Ag(I), the strongest π contact former, quenches the fluorescence of cdpa, apart from paramagnetic Cu(II) and Ni(II), which quench fluorescence by a redox mechanism not requiring π contacts. The structures of [Ag(cdpa)NO3] (1), [Pb(cdpa)(NO3)2] (2), [Zn(cdpa)(NO3)2] (3), [Cd(cdpa)Cl2]2 (4), [Cd(cdpa)2H2O](NO3)2 (5), and [Hg(cdpa)2H2O](NO3)2 (6) are reported. Structure 1 shows that Ag(I) is the only metal ion studied that forms π contacts with the fluorophore of cdpa in the solid state: Ag···C η(2) π contacts of 3.083 and 3.095 Å, in line with quenching of the fluorescence of the Ag(I)(cdpa) complex. In contrast, Pb(II), Zn(II), and Cd(II) show chelation-enhanced fluorescence in their cdpa complexes, and the structures of 2-4 show that the fluorophore of cdpa in each case forms no π contacts. By contrast, the adpa complexes of Pb(II) and Cd(II) show π contacts with its more strongly π-contacting fluorophore (Inorg. Chem. 2014, 53, 9014). The structures of 5 and 6 show bis-complexes of cdpa: the coordination geometries of Cd(II) and Hg(II) are discussed in relation to the number of covalently bound donor atoms present. The preferred hapticity of π-contacted metal ions is evaluated from the literature structures, suggesting that d(10) metal ions such as Ag(I) and Hg(II), and tetragonally distorted Cu(II) and Pd(II), prefer η(1) and η(2) π contacts, while more ionically bound metal ions such as K(I), Ba(II), and La(III), as well as d(10)s(2) metal ions such as Tl(I), Pb(II), and Bi(III), prefer η(6) contacts.

Highlight Nitrogen deficiency induces extensive metabolic adjustment in barley leaves mediated largely by sugar signalling and receptor-like kinase cascades that overlap with biotic stress pathways to induce aphid resistance., Agricultural nitrous oxide (N2O) pollution resulting from the use of synthetic fertilizers represents a significant contribution to anthropogenic greenhouse gas emissions, providing a rationale for reduced use of nitrogen (N) fertilizers. Nitrogen limitation results in extensive systems rebalancing that remodels metabolism and defence processes. To analyse the regulation underpinning these responses, barley (Horedeum vulgare) seedlings were grown for 7 d under N-deficient conditions until net photosynthesis was 50% lower than in N-replete controls. Although shoot growth was decreased there was no evidence for the induction of oxidative stress despite lower total concentrations of N-containing antioxidants. Nitrogen-deficient barley leaves were rich in amino acids, sugars and tricarboxylic acid cycle intermediates. In contrast to N-replete leaves one-day-old nymphs of the green peach aphid (Myzus persicae) failed to reach adulthood when transferred to N-deficient barley leaves. Transcripts encoding cell, sugar and nutrient signalling, protein degradation and secondary metabolism were over-represented in N-deficient leaves while those associated with hormone metabolism were similar under both nutrient regimes with the exception of mRNAs encoding proteins involved in auxin metabolism and responses. Significant similarities were observed between the N-limited barley leaf transcriptome and that of aphid-infested Arabidopsis leaves. These findings not only highlight significant similarities between biotic and abiotic stress signalling cascades but also identify potential targets for increasing aphid resistance with implications for the development of sustainable agriculture.

Steric, thermodynamic, and spectroscopic consequences of a stereochemically active lone pair (Lp) in Pb(II) complexes are discussed. The structure of Na3[Pb(dota)]NO3·2H2O (dota = 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetate) is reported: the four Pb–N bonds average 2.665 A, while the four Pb–O bonds to the acetate groups average 2.772 A. Normally, M–N bond lengths are longer than M–O bond lengths, as reported for the Sr(II) dota complex. This reversal in bond length order is attributed to the Pb–O bonds being closer to a stereochemically active Lp on Pb(II). In line with the latter, a very long Pb⋯O contact of 3.022 A is found to a water molecule coordinated over the proposed site of the Lp on Pb in its dota complex. Steric control of whether the Lp is stereochemically active, that produces long Pb–N bonds close to 2.8 A in length, can be exerted by ligands such as cryptands that prevent the N donors of the ligand from coordinating close together near the site on the Pb(II) opposite the Lp, the ‘antipodal’ site. The intense band that occurs in the electronic spectrum of Pb(II) complexes in the range 210–270 nm, that is attributed to a 6s2 → 6sp transition, is examined. The band shifts from 209 nm in the Pb2+(aq) ion in aqueous solution to about 260 nm as the number of N donors increases in a series of ligands containing only N and O donors. Within this shift it is found that in Pb(II) complexes with the same number of N donors, there is a shift to shorter wavelength, that appears to correlate with a change in the Lp from stereochemically inactive to stereochemically active. DFT calculations support the idea that the observed band in Pb(II) complexes is due to a transition from the filled 6s orbital to an empty 6p orbital, and suggest that the 6s orbital increasingly becomes hybridized with the 6p orbital as the Lp becomes more stereochemically active. The DFT calculations also support the interpretation that for complexes with the same number of N donors, the 6s2 → 6sp transition shifts to shorter wavelength as the Lp becomes stereochemically active.