Dehydration of a crystal hydrate at subglacial temperatures.

Water is one of the most important substances on our planet1. It is ubiquitous in its solid, liquid and vaporous states and all known biological systems depend on its unique chemical and physical properties. Moreover, many materials exist as water adducts, chief among which are crystal hydrates (a specific class of inclusion compound), which usually retain water indefinitely at subambient temperatures2. We describe a porous organic crystal that readily and reversibly adsorbs water into 1-nm-wide channels at more than 55% relative humidity. The water uptake/release is chromogenic, thus providing a convenient visual indication of the hydration state of the crystal over a wide temperature range. The complementary techniques of X-ray diffraction, optical microscopy, differential scanning calorimetry and molecular simulations were used to establish that the nanoconfined water is in a state of flux above -70 °C, thus allowing low-temperature dehydration to occur. We were able to determine the kinetics of dehydration over a wide temperature range, including well below 0 °C which, owing to the presence of atmospheric moisture, is usually challenging to accomplish. This discovery unlocks opportunities for designing materials that capture/release water over a range of temperatures that extend well below the freezing point of bulk water.

The gain-of-function mutation blf13 in the barley orthologue of the rice growth regulator NARROW LEAF1 is associated with increased leaf width.

Canopy architecture in cereals plays an important role in determining yield. Leaf width represents one key aspect of this canopy architecture. However, our understanding of leaf width control in cereals remains incomplete. Classical mutagenesis studies in barely identified multiple morphological mutants, including those with differing leaf widths. Of these, we characterized the broad leaf13 (blf13) mutant in detail. Mutant plants form wider leaves due to increased post-initiation growth and cell proliferation. The mutant phenotype perfectly co-segregated with a missense mutation in the HvHNT1 gene which affected a highly conserved region of the encoded protein, orthologous to the rice NARROW LEAF1 (NAL1) protein. Causality of this mutation for the blf13 phenotype is further supported by correlative transcriptomic analyses and protein-protein interaction studies showing that the mutant HvNHT1 protein interacts more strongly with a known interactor than wild-type HvHNT1. The mutant HvHNT1 protein also showed stronger homodimerization compared with wild-type HvHNT1, and homology modelling suggested an additional interaction site between HvHNT1 monomers due to the blf13 mutation. Thus, the blf13 mutation parallels known gain-of-function NAL1 alleles in rice that increase leaf width and grain yield, suggesting that the blf13 mutation may have a similar agronomic potential in barley.

Specific Noncovalent Association of Truncated exo-Functionalized Triangular Homochiral Isotrianglimines through Head-to-Head, Tail-to-Tail, and Honeycomb Supramolecular Motifs.

Chiral isotrianglimines were synthesized by the [3 + 3] cyclocondensation of (R,R)-1,2-diaminocyclohexane with C5-substituted isophthalaldehyde derivatives. The substituent's steric and electronic demands and the guest molecules' nature have affected the conformation of individual macrocycles and their propensity to form supramolecular architectures. In the crystal, the formation of a honeycomb-like packing arrangement of the simplest isotrianglimine was promoted by the presence of toluene or para-xylene molecules. A less symmetrical solvent molecule might force this arrangement to change. Polar substituents present in the macrocycle skeleton have enforced the self-association of isotrianglimines in the form of tail-to-tail dimers. These dimers could be further arranged in higher-order structures of the head-to-head type, which were held together by the solvent molecules. Non-associating isotrianglimine formed a container that accommodated acetonitrile molecules in its cavity. The calculated dimerization energies have indicated a strong preference for the formation of tail-to-tail dimers over those of the capsule type.

Symmetry-driven diastereoselective functionalization of simple trianglamine.

We have found that derivatization of the trianglamine macrocycle by aliphatic aldehydes leads selectively to one of the two possible diastereomeric aminal products. X-ray analysis, NMR measurements and DFT calculations pointed to the product possessing a higher symmetry.

Whole Exome Sequencing-Based Identification of a Novel Gene Involved in Root Hair Development in Barley (Hordeum vulgare L.).

Root hairs play a crucial role in anchoring plants in soil, interaction with microorganisms and nutrient uptake from the rhizosphere. In contrast to Arabidopsis, there is a limited knowledge of root hair morphogenesis in monocots, including barley (Hordeum vulgare L.). We have isolated barley mutant rhp1.e with an abnormal root hair phenotype after chemical mutagenesis of spring cultivar 'Sebastian'. The development of root hairs was initiated in the mutant but inhibited at the very early stage of tip growth. The length of root hairs reached only 3% of the length of parent cultivar. Using a whole exome sequencing (WES) approach, we identified G1674A mutation in the HORVU1Hr1G077230 gene, located on chromosome 1HL and encoding a cellulose synthase-like C1 protein (HvCSLC1) that might be involved in the xyloglucan (XyG) synthesis in root hairs. The identified mutation led to the retention of the second intron and premature termination of the HvCSLC1 protein. The mutation co-segregated with the abnormal root hair phenotype in the F2 progeny of rhp1.e mutant and its wild-type parent. Additionally, different substitutions in HORVU1Hr1G077230 were found in four other allelic mutants with the same root hair phenotype. Here, we discuss the putative role of HvCSLC1 protein in root hair tube elongation in barley.

Cytogenetic and molecular genotyping in the allotetraploid Festuca pratensis × Lolium perenne hybrids.

BACKGROUND: Species of the Festuca and Lolium genera, as well as intergeneric Festuca × Lolium (Festulolium) hybrids, are valuable fodder and turf grasses for agricultural and amenity purposes worldwide. Festulolium hybrids can merge in their genomes agronomically important characteristics. However, in polyploid plants, especially in allopolyploids, the hybridization of divergent genomes could contribute to various abnormalities, such as variability in chromosome number, structural rearrangements, and/or disorders in inheritance patterns. Here we studied these issues in allotetraploid Festuca pratensis × Lolium perenne hybrids. RESULTS: Cytogenetic procedures, including fluorescent in situ hybridization, genomic in situ hybridization, and molecular markers - inter-simple sequence repeats (ISSR) were exploited. This cytogenetic approach indicated the dynamics in the number and distribution of ribosomal RNA genes and structural rearrangements for both parental genomes (Festuca and Lolium) in hybrid karyotypes. The separate analysis of F. pratensis and L. perenne chromosomes in hybrid plants (F2-F3 generations of F. pratensis × L. perenne) revealed the asymmetrical level of rearrangements. Recognized structural changes were mainly located in the distal part of chromosome arms, and in chromosomes bearing ribosomal DNA, they were more frequently mapped in arms without this sequence. Based on the ISSR markers distribution, we found that the tetrasomic type of inheritance was characteristic for the majority of ISSR loci, but the disomic type was also observed. Nonetheless, no preference in the transmission of either Festuca or Lolium alleles to the following generations of allotetraploid F. pratensis × L. perenne hybrid was observed. CONCLUSION: Our study reports cytogenetic and molecular genotyping of the F. pratensis × L. perenne hybrid and its following F2-F3 progenies. The analysis of 137 allotetraploid F. pratensis × L. perenne hybrids revealed the higher level of recombination in chromosomes derived from F. pratensis genome. The results of ISSR markers indicated a mixed model of inheritance, which may be characteristic for these hybrids.

Genetic and Physiological Dissection of Photosynthesis in Barley Exposed to Drought Stress.

Balanced photosynthesis under drought is essential for better survival and for agricultural benefits in terms of biomass and yield. Given the current attempts to improve the photosynthetic efficiency for greater crop yield, the explanation of the genetic basis of that process, together with the phenotypic analysis, is significant in terms of both basic studies and potential agricultural application. Therefore, the main objective of this study was to uncover the molecular basis of the photosynthesis process under drought stress in barley. To address that goal, we conducted transcriptomic examination together with detailed photosynthesis analysis using the JIP-test. Using this approach, we indicated that photosynthesis is a process that is very early affected in barley seedlings treated with severe drought stress. Rather than focusing on individual genes, our strategy was pointed to the identification of groups of genes with similar expression patterns. As such, we identified and annotated almost 150 barley genes as crucial core-components of photosystems, electron transport components, and Calvin cycle enzymes. Moreover, we designated 17 possible regulatory interactions between photosynthesis-related genes and transcription factors in barley. Summarizing, our results provide a list of candidate genes for future genetic research and improvement of barley drought tolerance by targeting photosynthesis.

Insights into Barley Root Transcriptome under Mild Drought Stress with an Emphasis on Gene Expression Regulatory Mechanisms.

Root systems play a pivotal role in coupling with drought stress, which is accompanied with a substantial transcriptome rebuilding in the root tissues. Here, we present the results of global gene expression profiling of roots of two barley genotypes with contrasting abilities to cope with drought that were subjected to a mild level of the stress. We concentrate our analysis on gene expression regulation processes, which allowed the identification of 88 genes from 39 families involved in transcriptional regulation in roots upon mild drought. They include 13 genes encoding transcription factors (TFs) from AP2 family represented by ERFs, DREB, or B3 domain-containing TFs, eight WRKYs, six NACs, five of the HD-domain, MYB or MYB-related, bHLH and bZIP TFs. Also, the representatives of C3H, CPP, GRAS, LOB-domain, TCP, Tiffy, Tubby, and NF-Ys TFs, among others were found to be regulated by the mild drought in barley roots. We found that drought tolerance is accompanied with a lower number of gene expression changes than the amount observed in a susceptible genotype. The better drought acclimation may be related to the activation of transcription factors involved in the maintenance of primary root growth and in the epigenetic control of chromatin and DNA methylation. In addition, our analysis pointed to fives TFs from ERF, LOB, NAC, WRKY and bHLH families that may be important in the mild but not the severe drought response of barley roots.

Gene expression regulation in roots under drought.

Stress signalling and regulatory networks controlling expression of target genes are the basis of plant response to drought. Roots are the first organs exposed to water deficiency in the soil and are the place of drought sensing. Signalling cascades transfer chemical signals toward the shoot and initiate molecular responses that lead to the biochemical and morphological changes that allow plants to be protected against water loss and to tolerate stress conditions. Here, we present an overview of signalling network and gene expression regulation pathways that are actively induced in roots under drought stress. In particular, the role of several transcription factor (TF) families, including DREB, AP2/ERF, NAC, bZIP, MYC, CAMTA, Alfin-like and Q-type ZFP, in the regulation of root response to drought are highlighted. The information provided includes available data on mutual interactions between these TFs together with their regulation by plant hormones and other signalling molecules. The most significant downstream target genes and molecular processes that are controlled by the regulatory factors are given. These data are also coupled with information about the influence of the described regulatory networks on root traits and root development which may translate to enhanced drought tolerance. This is the first literature survey demonstrating the gene expression regulatory machinery that is induced by drought stress, presented from the perspective of roots.

Transcriptome analysis reveals the role of the root hairs as environmental sensors to maintain plant functions under water-deficiency conditions.

An important part of the root system is the root hairs, which play a role in mineral and water uptake. Here, we present an analysis of the transcriptomic response to water deficiency of the wild-type (WT) barley cultivar 'Karat' and its root-hairless mutant rhl1.a. A comparison of the transcriptional changes induced by water stress resulted in the identification of genes whose expression was specifically affected in each genotype. At the onset of water stress, more genes were modulated by water shortage in the roots of the WT plants than in the roots of rhl1.a. The roots of the WT plants, but not of rhl1.a, specifically responded with the induction of genes that are related to the abscisic acid biosynthesis, stomatal closure, and cell wall biogenesis, thus indicating the specific activation of processes that are related to water-stress signalling and protection. On the other hand, the processes involved in the further response to abiotic stimuli, including hydrogen peroxide, heat, and high light intensity, were specifically up-regulated in the leaves of rhl1.a. An extended period of severe stress caused more drastic transcriptome changes in the roots and leaves of the rhl1.a mutant than in those of the WT. These results are in agreement with the much stronger damage to photosystem II in the rhl1.a mutant than in its parent cultivar after 10 d of water stress. Taking into account the putative stress sensing and signalling features of the root hair transcriptome, we discuss the role of root hairs as sensors of environmental conditions.

Readily prepared inclusion forming chiral calixsalens.

Calixsalens, chiral triangular hexaimines are readily synthesized by [3 + 3] cyclocondensation of trans-(R,R)-1,2-diaminocyclohexane with 2-hydroxyisophthalaldehyde derivatives. The usually rigid calixsalen ring is able to invert its conformation as a consequence of steric repulsion between bulky substituents at the C5 positions of the aromatic rings. The steric and electronic nature of the substituents does not affect only the conformation of the macrocycle. Small polar substituents enforce dimeric self-association to form an apohost where each of the monomers simultaneously serves as the host and the guest of its partner. Non-associating calixsalens form assemblies in which two symmetry-related molecules are arranged in a head-to-head fashion to form a capsule, or unimolecular cages that are able to entrap solvent molecules in their intrinsic voids.

Intramolecular interactions of trityl groups.

Trityl group, Tr, is a molecular dynamic rotor of which the conformation and helicity depend on other groups in the close vicinity. Interactions with another covalently linked Tr group and with other substituents are analyzed in terms of transfer of chirality to the trityl group. Two trityl groups in a molecule can mutually interact at a distance of two, three, or five bonds. Despite its size, a Tr group attached to a cyclohexane or cyclopentane ring through an oxygen or nitrogen atom adopts either an axial or equatorial position, depending on additional stabilizing interactions, such as hydrogen bonding.

Vascular endothelial growth factor-A signaling in bone marrow-derived endothelial progenitor cells exposed to hypoxic stress.

Bone marrow-derived endothelial progenitor cells (BM-EPCs) are stimulated by vascular endothelial growth factor-A (VEGF-A) and other potent proangiogenic factors. During angiogenesis, an increase in VEGF-A expression stimulates BM-EPCs to enhance endothelial tube formation and contribute to an increase in microvessel density. Hypoxia is known to produce an enhanced angiogenic response and heightened levels of VEGF-A have been seen in oxygen deprived epithelial and endothelial cells, yet the pathways for VEGF-A signaling in BM-EPCs have not been described. This study explores the influence of hypoxia on VEGF-A signaling in rat BM-EPCs utilizing a novel proteomic strategy to directly identify interacting downstream components of the combined VEGF receptor(s) signaling pathways, gene expression analysis, and functional phenotyping. VEGF-A signaling network analysis following liquid chromatographic separation and tandem mass spectrometry revealed proteins related to inositol/calcium signaling, nitric oxide signaling, cell survival, cell migration, and inflammatory responses. Alterations in BM-EPC expression of common angiogenic genes and tube formation in response to VEGF-A during hypoxia were measured and combined with the proteomic analysis to enhance and support the signaling pathways detected. BM-EPC tube formation assays in response to VEGF-A exhibited little tube formation; however, a cell projection/migratory phenotype supported the signaling data. Additionally, a novel assay measuring BM-EPC incorporation into preformed endothelial cell tubes indicated a significant increase of incorporated BM-EPCs after pretreatment with VEGF-A during hypoxia. This study verifies known VEGF-A pathway components and reveals several unidentified mechanisms of VEGF-A signaling in BM-EPCs during hypoxia that may be important for migration to sites of vascular regeneration.

Shape-Memory Effect Triggered by π-π Interactions in a Flexible Terpyridine Metal-Organic Framework.

Shape-memory polymers and alloys are adaptable materials capable of reversing from a deformed, metastable phase to an energetically favored original phase in response to external stimuli. In the context of metal-organic frameworks, the term shape-memory is defined as the property of a switchable framework to stabilize the reopened pore phase after the first switching transition. Herein we describe a novel flexible terpyridine MOF which, upon desolvation, transforms into a nonporous structure that reopens into a shape-memory phase when exposed to CO2 at 195 K. Based on comprehensive in situ experimental studies (SC-XRD and PXRD) and DFT energetic considerations combined with literature reports, we recommend dividing shape-memory MOFs into two categories, viz responsive and nonresponsive, depending on the transformability of the gas-free reopened pore phase into the collapsed phase. Furthermore, considering the methodological gap in discovering and understanding shape-memory porous materials, we emphasize the importance of multicycle physisorption experiments for dynamic open framework materials, including metal-organic and covalent organic frameworks.

From single molecule to crystal: mapping out the conformations of tartaric acids and their derivatives.

Stereoisomers of one of the most important organic compounds, tartaric acid, optically active and meso as well as the ester or amide derivatives, can show diverse structures related to the rotation around the three carbon-carbon bonds. This study determines the controlling factors for conformational changes of these molecules in vacuo, in solution, and in the crystalline state using DFT calculations, spectroscopic measurements, and X-ray diffraction. All structural variations can be logically accounted for by the possibility of formation and breaking of hydrogen bonds between the hydroxy or amide donors and oxygen acceptors, among these the hydrogen bonds that close five-membered rings being the most stable. These findings are useful in designing molecular and crystal structures of highly polar, polyfunctional, chiral compounds.

Poly[(µ(2)-2-amino-pyrimidine-κ(2)N(1):N(3))di-µ(2)-chlorido-mercury(II)].

The title compound, [HgCl(2)(C(4)H(5)N(3))](n), features a two-dimensional network parallel to (001) that is based on an Hg(II) atom octahedrally coordinated by four µ(2)-Cl atoms and two µ(2)-2-amino-pyrimidine (apym) ligands in trans positions, yielding a distorted HgCl(4)N(2) octa-hedron. The coordination network can be described as an uninodal 4-connected net with the sql topology. The Hg(II) ion lies on a site of -1 symmetry and the apym ligand lies on sites of m symmetry with the mirror plane perpendicular to the pyrimidine plane and passing through the NH(2) group N atom. This polymeric structure is stabilized by N-H⋯Cl hydrogen bonds and columnar π-π stacking of pyrimidine rings, with a centroid-centroid distance of 3.832 (2) Å.

Controlled, Sunlight-Driven Reversible Cycloaddition of Multiple Singlet Oxygen Molecules to Anthracene-Containing Trianglimine Macrocycles.

Controlled release of singlet oxygen is of interest not only to chemists, but also to biologists and medics involved in cancer therapy. Two chiral polyaza macrocyclic compounds and their corresponding endoperoxides have been synthesized. These peroxides exhibit high temperature stability, up to 80 °C. Detailed studies on their structure, including X-ray analysis as well as NMR, UV-VIS ECD spectroscopy and theoretical calculations, combined with photochemical measurements indicate that their high stability is related to the arrangement of oxygen atoms in a conformationally stable macrocyclic ring. Despite the change of carbon hybridization from sp2 to sp3 at the 9 and 10 positions of the anthracene units, the macrocyclic skeleton of the obtained compounds does not change its conformation. The obtained endoperoxides can be formed and release singlet oxygen by irradiation with UV light of 365 and 275 nm, respectively. Release of the oxygen does not degrade the macrocyclic structure.

Synthesis, structural studies and biological properties of some phosphono-perfluorophenylalanine derivatives formed by SNAr reactions.

Several novel phosphono-perfluorophenylalanine derivatives, as mimetics of phenylalanine, were synthesized by subjecting diethyl (2-(perfluorophenyl)-1-(phenylamino)ethyl)-phosphonate to SNAr reactions with different types of nucleophiles such as thiols, amines and phenols. The structure of the products was confirmed using spectroscopic and spectrometric techniques. For two compounds X-ray single crystal diffraction analysis and DFT investigations were performed providing information in regard to the preferable conformation, hydrogen bonds and other interactions. The antiproliferative potency of some of the new phosphono-perfluorophenylalanine derivatives obtained as well as representatives of previously synthesized perfluorophenyl phosphonate analogues of phenylalanine was studied on selected glioma cell lines. Preliminary evaluation of the compounds drug likeness was examined with respect to Lipinski's and Veber's rules, and showed that they meet the criteria perfectly. MTT (3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide) assay results demonstrated that the compounds exhibit moderate activity against the glioblastoma multiforme cell lines (T98G and U-118 MG). Moreover most of the studied SNAr reaction products displayed significantly higher inhibitory activity against both cancer cell lines than the parent diethyl (2-(perfluorophenyl)-1-(phenylamino)ethyl)phosphonate.

A thermo-responsive structural switch and colossal anisotropic thermal expansion in a chiral organic solid.

Trianglimine, a chiral triangular-shaped hexaimine, exists in at least three apohost polymorphic forms. Form I had been previously obtained by crystallisation from a mixture of dichloromethane and acetonitrile and we have now crystallised Form II from acetone. Both forms possess similar packing arrangements, but Form II undergoes a reversible phase transition to Form III, as well as colossal anisotropic positive thermal expansion. Form I does not exhibit any remarkable thermal properties.

Sterically Crowded Trianglimines-Synthesis, Structure, Solid-State Self-Assembly, and Unexpected Chiroptical Properties.

The chiral, triangular-shape hexaimine macrocycles (trianglimines), bearing bulky alkynyl or aryl substituents were synthesized and studied by means of experimental and theoretical methods. The macrocyclization reactions are driven by the extraordinary stability of the trianglimine ring and provided products with high yields. Electrostatic repulsion between imine nitrogen atoms and the substituents forced an anti conformation of the aromatic linkers. Although the DFT-optimized structure of 7 is D3 symmetrical, in the crystal, the macrocycle adopts a bowl-like molecular shape. The macrocycle self-assembles into tail-to-tail dimers by mutual interdigitation of aromatic moieties. In contrast, macrocycle 8 adopts a rigid pillararene-like conformation. The nature of the substituent significantly affects the electronic properties of the linker. As a result, unexpectedly high exciton Cotton effects are observed in the electronic circular dichroism (ECD) spectra. The origin of these effects was subject of an in-depth study.