Host Wall Research Articles

Taming Tris(bipyridine)ruthenium(II) and Its Reactions in Water by Capture/Release with Shape-Switchable Symmetry-Matched Cyclophanes.

Electron/proton transfers in water proceeding from ground/excited states are the elementary reactions of chemistry. These reactions of an iconic class of molecules—polypyridineRu(II)—are now controlled by capturing or releasing three of them with hosts that are shape-switchable. Reversible erection or collapse of the host walls allows such switchability. Some reaction rates are suppressed by factors of up to 120 by inclusive binding of the metal complexes. This puts nanometric coordination chemistry in a box that can be open or shut as necessary. Such second-sphere complexation can allow considerable control to be exerted on photocatalysis, electrocatalysis, and luminescent sensing involving polypyridineRu(II) compounds. The capturing states of hosts are symmetry-matched to guests for selective binding and display submicromolar affinities. A perching complex, which is an intermediate state between capturing and releasing states, is also demonstrated.

Encapsulating electron-deficient dyes into metal-organic capsules to achieve high reduction potentials.

The design of artificial supramolecular systems that mimic the structure and functionality of natural enzymes to achieve efficient chemical conversions is a promising subject. In this work, we assembled a novel metal-organic capsule from electron-rich dyes, polyaniline compounds, as ligands by a subcomponent self-assembly strategy. By encapsulating electron-deficient dyes, anthraquinone or 9,10-dicyanoanthracene, into electron-rich pseudo-cubic capsules, we successfully constructed an artificial enzyme-mimicking supramolecular system for the efficient photocatalytic reduction of aryl chlorides with high reduction potentials (Ered < -2.0 V) via multiphoton excitation. Within the confined space of the host, the electron-deficient dyes were forced to come into contact intimately with the electron-rich host walls, which facilitates the photoinduced electron transfer process. Moreover, we achieved quantitative yields in the photocatalytic reduction reaction under mild conditions within 30 minutes, which was rarely reported in the previous literature in terms of reaction efficiency. This study provides a general and valuable strategy for activating inert substrates, which may have potential applications in solar energy conversion and enzyme-mimicking catalysis in the chemical industry.

Parasitoid chytridiomycete Ericiomyces syringoforeus gen. et sp. nov. has unique cellular structures to infect the host

Many fungi have been identified as pathogens of marine algae. Among them, Chytridiomycota have been revealed as relatively highly abundant, but much of the diversity known within these groups is almost entirely based on environmental sequencing data. Here, we present a novel chytridiomycete genus and species, characterized by light microscopical observations, ultrastructure, and molecular phylogenetic analysis of the parasitic chytrid of brackish-water dinoflagellate Kryptoperidinium foliaceum from the Baltic Sea. Phylogenetic analysis of rDNA sequences and the ultrastructure of the strain reveals that it represents a new family in the order Rhizophydiales. Ericiomyces syringoforeus gen. et sp. nov. is a parasitoid with a life cycle composed by zoospores, which attach to the host, encyst, and produce a rhizoidal system (haustorium). Unlike typical Rhizophydiales chytrids, sporangium develops as a lateral outgrowth of the encysted zoospore. The ultrastructural study revealed at least two unique traits: the syringe-like organelle in the cyst, which supposed to paralyze the host, and funnel-shaped structure anchoring sporangium in the host wall. Sporangium matures and produces new zoospores within 3 days. Multiple infections are common and then the life cycle is 1–2 days shorter compared to the duration when a single infection occurred. Cross-infection experiments showed that E. syringoforeus could only infect dinoflagellates, being K. foliaceum highly susceptible to infection by the chytrid parasitoid. The effects of some fungal epidemics on populations of Kryptoperidinium are discussed.

Deciphering interfungal relationships in the 410-million-yr-old Rhynie chert: Brijax amictus gen. et sp. nov. (Chytridiomycota) colonizing the walls of glomeromycotan acaulospores

Glomeromycotan spores from the Early Devonian Rhynie chert frequently contain evidence of colonization by other fungi. However, relatively few of these relationships have been described and evaluated. Brijax amictus gen. et sp. nov., a probable chytrid (Chytridiomycota) associated with certain thick-walled archaeosporalean acaulospores from the Rhynie chert, develops largely within the host spore wall. Thalli are eucarpic, monocentric, 16.5–40(−50) μm high, and consist of an inoperculate sporangium (zoosporangium or resting spore stage) located in the outer, ephemeral spore wall component, and a rhizoidal system that extends into the persistent spore wall. Sporangia that, at maturity, are completely surrounded by the host spore wall develop a prominent discharge tube, whereas ones not covered by the host wall have simple openings or pores. Thallus morphology resembles certain present-day species of Rhizophydium (Rhizophydiales) and Phlyctochytrium (Chytridiales); however, the systematic affinities of B. amictus remain unresolved. This discovery contributes to the understanding of the various levels of interfungal relationship that existed in early terrestrial ecosystems.

What is the driving force behind molecular triangles and their guests? A quantum chemical perspective about host-guest interactions.

The physical nature of host-guest (HG) interactions occurring between molecular triangles and linear anions was explored using density functional theory (DFT) calculations combined with energy decomposition analyses (EDA), nuclear independent chemical shift (NICS), and non-covalent interaction index (NCI). We demonstrate that: (i) in addition to the host being significantly rigid, the strain energies are not negligible, especially for host 2; (ii) halogen anions interact mainly by electrostatic forces (ΔEelst > ΔE > ΔEdisp), meanwhile; (iii) trihalogen anions interact mostly by dispersion forces (ΔEdisp > ΔEelst≈ΔE). The NICS and NCI calculations corroborate the idea that HG interactions are considerably mediated through dispersion terms, and also indicate an antiaromatic character inside the host walls.

A tiny parasite of unicellular microorganisms from the Lower Devonian Rhynie and Windyfield cherts, Scotland

Small inclusions of clear chert within silicified substrate from the Lower Devonian Rhynie and Windyfield localities in Scotland contain several different types of microbial fossils. The commonest type, formally described in this study as Anechosoma oblongum nov. gen. et sp., is a simple unicellular organism, ellipsoidal to oblong, smooth-walled, and <20 μm long, with possible affinities to the Glaucophyta or Chlorophyta. A thin-walled envelope surrounds some of the specimens; others occur in clusters of 2–8 within a common envelope. Approximately 10% of the specimens are infected by Rhyniovexator penetrans nov. gen. et sp., a tiny parasite – perhaps a chytrid or member of the Aphelida – consisting of an epibiotic, spheroidal vesicle <4 μm in diameter on a long, narrow, tubular structure that breaches the host wall. Although the systematic affinities of A. oblongum and R. penetrans cannot be fully evaluated, this discovery provides important new information on the intricate relationships that existed between the different constituents of the microbial communities comprising the plankton in pools and ponds and colonizing various surfaces in the Rhynie paleoecosystem.

Survivorship and walking behavior of Inquilinitermes microcerus (Termitidae: Termitinae) in contact with host workers and walls from host nest

Constrictotermes sp. nests are frequently inhabited by colonies of Inquilinitermes microcerus. In this association, I. microcerus colonies usually establish their colonies spatially isolated from Constrictotermes colonies. Here, we investigated whether the apparent spatial isolation of I. microcerus colonies in Constrictotermes nests should be related to their needs (e.g. feeding) in relation to the central part of the nest or to a possible stress provoked by the presence of the host. For this, survival and walking behavior bioassays were performed to test the hypothesis that the survivorship of inquilines is: (i) reduced in the presence of host, mainly of those from different nests, (ii) increased in contact with inner walls compared with external walls; and that the distance walked and walking velocity of inquiline is: (iii) increased in the presence of the host and (iv) reduced in contact with the internal walls compared with external walls of host nest. The mean time to death of inquiline workers is lower in contact with host (independently from the same or different nest) compared with control and the mean time to death of inquiline workers is lower in contact with external walls of host nest compared with control group and the inner walls. The distance walked and walking velocity of inquiline workers in contact with their hosts (from the same or different nest) did not differ from control, however, these parameters were reduced when workers were in contact with inner and external walls compared with control. In general, our results showed that I. microcerus adopt behavioral strategies to avoid perception by its host.

Invited commentary

Computational studies of carotid artery hemodynamics have been performed for almost three decades. We now know that the localized arterial dilation found exclusively in the carotid bulb produces disturbed flow patterns with low and oscillatory shear stress that can alter endothelial function and activate atherogenic cellular phenotypes. Intensified by the deleterious effects of systemic risk factors and high intramural stresses and strains, these hemodynamic conditions can stimulate arterial wall stiffening and thickening that can further perturb normal physiology. This vicious circle of abnormal hemodynamics and pathologic remodeling may produce plaques that can become unstable, presenting vascular surgeons with opportunities to intervene. Two of the most commonly used variations on the technique of carotid endarterectomy are primary closure and patch angioplasty. Whereas clinical evidence has historically advocated for patch use,1Brott T.G. Halperin J.L. Abbara S. Bacharach J.M. Barr J.D. Bush R.L. et al.2011 ASA/ACCF/AHA/AANN/AANS/ACR/ASNR/CNS/SAIP/SCAI/SIR/SNIS/SVM/SVS Guideline on the Management of Patients With Extracranial Carotid and Vertebral Artery Disease: a report of the American College of Cardiology Foundation/American Heart Association Task F.Circulation. 2011; 124: e54-e130Crossref PubMed Scopus (453) Google Scholar recent data suggest that benefits are only of borderline significance2Rerkasem K. Rothwell P.M. Systematic review of randomized controlled trials of patch angioplasty versus primary closure and different types of patch materials during carotid endarterectomy.Asian J Surg. 2011; 34: 32-40Crossref PubMed Scopus (68) Google Scholar or may not even be significant at all.3Avgerinos E.D. Chaer R.A. Naddaf A. El-Shazly O.M. Marone L. Makaroun M.S. Primary closure after carotid endarterectomy is not inferior to other closure techniques.J Vasc Surg. 2016; 64: 678-683.e1Abstract Full Text Full Text PDF PubMed Scopus (21) Google Scholar This poses a question of whether increased clamp time, higher risk of cerebral ischemia, potential infectious issues, and patch-associated aneurysmal dilation are justified for every patient. In this study by Domanin et al, this argument is explored from a hemodynamic perspective whereby the authors compare flow characteristics in carotid arteries virtually repaired with primary closure and patch angioplasty. Because addition of the patch widened the carotid bifurcation, patch angioplasty was found to be associated with less favorable hemodynamics compared with primary closure. The authors conclude that patch use should be elective and performed with the purpose of re-creating the original shape of the carotid bifurcation rather than enlarging it. We arrived at similar conclusions in our computational analysis of carotid artery reconstruction, demonstrating more favorable flow patterns and lower intramural mechanical stresses for the artery repaired without a patch.4Kamenskiy A.V. Pipinos I.I. Dzenis Y.A. Gupta P.K. Jaffar Kazmi S.A. MacTaggart J.N. A mathematical evaluation of hemodynamic parameters after carotid eversion and conventional patch angioplasty.Am J Physiol Heart Circ Physiol. 2013; 305: H716-H724Crossref PubMed Scopus (19) Google Scholar To produce favorable hemodynamics with patching, our analysis demonstrated that the patch should be tailored to ensure smooth transition in arterial diameter, be placed anteriorly (as opposed to laterally), and be made of material that most closely matches the compliance of the recipient artery.5Kamenskiy A.V. MacTaggart J.N. Pipinos I.I. Gupta P.K. Dzenis Y.A. Hemodynamically motivated choice of patch angioplasty for the performance of carotid endarterectomy.Ann Biomed Eng. 2012; 41: 263-278Crossref PubMed Scopus (17) Google Scholar Patch compliance was particularly important as the mismatch in stiffness between synthetic patches and the host wall resulted in high stress and strain concentrations at the suture-artery interface, causing the posterior aspect of the artery to bulge out and to perturb flow and intramural stresses. Whereas these findings are merely suggestions offered by computational modeling, they have the potential to help clinicians choose the optimal type of repair material and geometry based on patient-specific arterial characteristics. Computational modeling of vascular physiology is frequently met by clinicians with skepticism as it is still in its infancy in describing complex mechanobiologic phenomena. There is much to be learned to improve fidelity of these models, and prospective validation in patients is a difficult next step to make these techniques clinically relevant. This cannot be achieved without synergistic collaborations between engineers and vascular surgeons. Sparking and nurturing these collaborations is the best way to make meaningful progress in making computational models useful to clinicians, as even the best of tools are only as good as the hands that use them. The opinions or views expressed in this commentary are those of the authors and do not necessarily reflect the opinions or recommendations of the Journal of Vascular Surgery or the Society for Vascular Surgery. Computational fluid dynamic comparison between patch-based and primary closure techniques after carotid endarterectomyJournal of Vascular SurgeryVol. 67Issue 3PreviewThe aim of the study was to provide, by means of computational fluid dynamics, a comparative analysis after carotid endarterectomy (CEA) between patch graft (PG) and primary closure (PC) techniques performed in real carotid geometries to identify disturbed flow conditions potentially involved in the development of restenosis. Full-Text PDF Open Archive

Deciphering interfungal relationships in the 410 million-year-old Rhynie chert: Glomoid spores under attack

Various types of other fungi colonize glomeromycotinan (Mucoromycota) spores in the Early Devonian Rhynie chert. However, relatively few of these associations have been described and evaluated in detail. One particular type of glomoid spore located in degrading land plant axes from the Rhynie chert provides evidence of (simultaneous) interaction with three different fungi. Massive callosities occur around the intrusion filaments of a chytrid-like parasite with epibiotic sporangia, while the hyphae of a delicate mycelial fungus extend into the spore lumen without triggering a recognizable host response. Several spores show large numbers of inwardly directed projections, which are regularly distributed and consist of a short hyphal branch encased in host wall material. The projections represent the penetration sites of a distinctive, mycelial fungus that forms a mantle-like hyphal sheath around the spores. This type of fungal interaction with glomeromycotinan spores has not previously been reported, and thus expands our knowledge of the numerous interfungal relationships that existed in early continental ecosystems.

Genome-wide transcriptional profiling of Botrytis cinerea genes targeting plant cell walls during infections of different hosts.

Cell walls are barriers that impair colonization of host tissues, but also are important reservoirs of energy-rich sugars. Growing hyphae of necrotrophic fungal pathogens, such as Botrytis cinerea (Botrytis, henceforth), secrete enzymes that disassemble cell wall polysaccharides. In this work we describe the annotation of 275 putative secreted Carbohydrate-Active enZymes (CAZymes) identified in the Botrytis B05.10 genome. Using RNAseq we determined which Botrytis CAZymes were expressed during infections of lettuce leaves, ripe tomato fruit, and grape berries. On the three hosts, Botrytis expressed a common group of 229 potentially secreted CAZymes, including 28 pectin backbone-modifying enzymes, 21 hemicellulose-modifying proteins, 18 enzymes that might target pectin and hemicellulose side-branches, and 16 enzymes predicted to degrade cellulose. The diversity of the Botrytis CAZymes may be partly responsible for its wide host range. Thirty-six candidate CAZymes with secretion signals were found exclusively when Botrytis interacted with ripe tomato fruit and grape berries. Pectin polysaccharides are notably abundant in grape and tomato cell walls, but lettuce leaf walls have less pectin and are richer in hemicelluloses and cellulose. The results of this study not only suggest that Botrytis targets similar wall polysaccharide networks on fruit and leaves, but also that it may selectively attack host wall polysaccharide substrates depending on the host tissue.

Enzymatic interactions between Gremmeniella abietina var. abietina, European race, and two resistant hosts, Pinus banksiana and P. contorta

SummaryUltrastructural observations showed that the European race of Gremmeniella abietina var. abietina can secrete several cell wall–degrading enzymes that help the invasion of Pinus banksiana and P. contorta shoot tip tissues. Alterations in the content or distribution of cellulose were obvious, indicating that colonization might be achieved primarily through the action of glucanases. Polygalacturonases seemed more abundant in the cortex and the phloem of the stem, suggesting they are among the first enzymes secreted by the pathogen during infection. Production of laccases and peroxidases was also revealed but always close to fungal cells or in areas where host wall degradation was obvious. In places where there was an accumulation of phenolic compounds in the infected zones of the shoot, particularly in or near the transition zone, immunolocalization of both enzymes was limited or absent. Laccases and polygalacturonases were regularly detected over the extracellular sheath of G. abietina, and this indicates that the sheath could play a significant role during host wall degradation. Finally, examination of G. abietina wall constituents, such as chitin and β‐1,3‐glucans, suggests that the composition of the pathogen wall changes during the infection process. This change may be associated with the secretion of fungal enzymes but could also be linked to host reactions altering the integrity of pathogen cell walls.

Light-Triggered Eradication of Acinetobacter baumannii by Means of NO Delivery from a Porous Material with an Entrapped Metal Nitrosyl

A photoactive manganese nitrosyl, namely [Mn(PaPy(3))(NO)](ClO(4)) ({Mn-NO}), has been loaded into the columnar pores of an MCM-41 host. Strong interaction between the polar nitrosyl and the -OH groups on the host wall leads to excellent entrapment of the NO donor within the porous host. With the aluminosilicate-based host (Al-MCM-41), the loading is further enhanced due to electrostatic interaction of the cationic species with the aluminum sites. The extent of loading has been determined via analytical techniques including N(2) adsorption/desorption isometry. Powder X-ray diffraction studies on the loaded materials afford patterns typical of an ordered mesoporous silicate consisting of a hexagonal array of unidimensional channels (with slight loss of crystallinity). Elemental mapping of the loaded particles confirms the incorporation of {Mn-NO} into the porous MCM-41 structure and attests to the homogeneity of the guest molecule distribution throughout individual particles. When suspensions of the loaded materials in saline solution are exposed to low-power (10-100 mW) visible light, rapid release of NO is observed. With continuous exposure, a steady release of 50-80 μM of NO is attained with 5 mg of material/mL buffer within 5 min, and the NO flux is maintained for a period of ~60 min. Rapid bursts of 5-10 μM NO are noted with short light pulses. Loss of either the nitrosyl or its photoproduct(s) from these materials in biological media is minimal over long periods of time. The NO release profiles suggest potential use of these powdery biocompatible materials as NO donors where the delivery of NO (a strong antibiotic) could be controlled via the exposure of light. Such prediction has been confirmed with the successful eradication of both drug-susceptible and drug-resistant Acinetobacter baumannii in a soft-tissue infection model through light-triggered NO delivery.

Mycena sp., a mycorrhizal fungus of the orchid Dendrobium officinale

An endophytic fungus, F-23, was isolated from the roots of Dendrobium officinale Kimura et Migo, an endangered Chinese medicinal plant. The sequence of the ITS region indicated that the isolate belongs to the genus Mycena. After 4 months of inoculation, the root systems of D. officinale that were inoculated with F-23 fungus were much larger than the control’s root systems. We also observed that the hyphae of F-23 penetrated the epidermal cells within the host’s roots and spread from cell to cell. A large number of pelotons existed in the root cortical cells of D. officinale inoculated with F-23 fungus. Intracellular hyphae crossing through the host walls were also observed using SEM (scanning electron microscopy). In contrast, light microscopy and SEM showed that the transverse sections of the roots of control plants remained uncolonized. Therefore, the F-23 fungus can form mycorrhizal associations with the roots of its host plant, D. officinale, and enhance the growth of seedlings and roots. In brief, Mycena sp. was identified and shown to be a mycorrhizal fungus of the epiphytic orchid, D. officinale. This might be of potential use to the mass cultivation of D. officinale under artificial conditions.

Immunohistochemical investigation of the necrotrophic phase of the fungus Colletotrichum gloeosporioides in the biocontrol of hemp sesbania (Sesbania exaltata; Papilionaceae)

Fungal plant pathogens exert much of their effect on plant cells through alterations in the host cell walls. However, obtaining biochemical proof for this change is difficult because of the relatively small number of cells that are affected by the pathogen relative to the bulk of host tissue. In this study, we examined the differences in host wall composition between infected and uninfected areas of seedlings of the weed hemp sesbania (Sesbania exaltata) that were treated with the biocontrol agent Colletotrichum gloeosporioides. • To determine the changes in cell wall composition, we used semi-thin sections and a battery of antibody probes that recognize components of the cell wall and immunogold-silver cytochemistry to visualize the probes. • A loss of specific plant cell wall polysaccharides in the region surrounding the primary fungal infection and the creation of a defensive layer by the plant to limit the fungal invasion were the two most obvious changes noted in this study. At the invasion site, there was significant loss of rhamnogalacturon-1 (RGI) and esterified and de-esterified homogalacturonan (HG)-reactive epitopes from the cell walls. In contrast, boundary tissue between the vascular tissue and the fungal lesion reacted more strongly with antibodies that recognize arabinogalactan proteins (AGPs) and xyloglucans than in unaffected areas. • These data strongly indicate a role of pectinases in the invasion of the biocontrol agent and the importance of extensins, AGPs, and xyloglucans as defense by the host.

The Spin Chemistry and Magnetic Resonance of H2@C60. From the Pauli Principle to Trapping a Long Lived Nuclear Excited Spin State inside a Buckyball

One of the early triumphs of quantum mechanics was Heisenberg's prediction, based on the Pauli principle and wave function symmetry arguments, that the simplest molecule, H(2), should exist as two distinct species-allotropes of elemental hydrogen. One allotrope, termed para-H(2) (pH(2)), was predicted to be a lower energy species that could be visualized as rotating like a sphere and possessing antiparallel ( upward arrow downward arrow) nuclear spins; the other allotrope, termed ortho-H(2) (oH(2)), was predicted to be a higher energy state that could be visualized as rotating like a cartwheel and possessing parallel ( upward arrow upward arrow) nuclear spins. This remarkable prediction was confirmed by the early 1930s, and pH(2) and oH(2) were not only separated and characterized but were also found to be stable almost indefinitely in the absence of paramagnetic "spin catalysts", such as molecular oxygen, or traces of paramagnetic impurities, such as metal ions. The two allotropes of elemental hydrogen, pH(2) and oH(2), may be quantitatively incarcerated in C(60) to form endofullerene guest@host complexes, symbolized as pH(2)@C(60) and oH(2)@C(60), respectively. How does the subtle difference in nuclear spin manifest itself when hydrogen allotropes are incarcerated in a buckyball? Can the incarcerated "guests" communicate with the outside world and vice versa? Can a paramagnetic spin catalyst in the outside world cause the interconversion of the allotropes and thereby effect a chemical transformation inside a buckyball? How close are the measurable properties of H(2)@C(60) to those computed for the "quantum particle in a spherical box"? Are there any potential practical applications of this fascinating marriage of the simplest molecule, H(2), with one of the most beautiful of all molecules, C(60)? How can one address such questions theoretically and experimentally? A goal of our studies is to produce an understanding of how the H(2) guest molecules incarcerated in the host C(60) can "communicate" with the chemical world surrounding it. This world includes both the "walls" of the incarcerating host (the carbon atom "bricks" that compose the wall) and the "outside" world beyond the atoms of the host walls, namely, the solvent molecules and selected paramagnetic molecules added to the solvent that will have special spin interactions with the H(2) inside the complex. In this Account, we describe the temperature dependence of the equilibrium of the interconversion of oH(2)@C(60) and pH(2)@C(60) and show how elemental dioxygen, O(2), a ground-state triplet, is an excellent paramagnetic spin catalyst for this interconversion. We then describe an exploration of the spin spectroscopy and spin chemistry of H(2)@C(60). We find that H(2)@C(60) and its isotopic analogs, HD@C(60) and D(2)@C(60), provide a rich and fascinating platform on which to investigate spin spectroscopy and spin chemistry. Finally, we consider the potential extension of spin chemistry to another molecule with spin isomers, H(2)O, and the potential applications of the use of pH(2)@C(60) as a source of latent massive nuclear polarization.

Microbe‐associated molecular pattern (MAMP) signatures, synergy, size and charge: influences on perception or mobility and host defence responses

Triggering of defences by microbes has mainly been investigated using single elicitors or microbe-associated molecular patterns (MAMPs), but MAMPs are released in planta as complex mixtures together with endogenous oligogalacturonan (OGA) elicitor. We investigated the early responses in Arabidopsis of calcium influx and oxidative burst induced by non-saturating concentrations of bacterial MAMPs, used singly and in combination: flagellin peptide (flg22), elongation factor peptide (elf18), peptidoglycan (PGN) and component muropeptides, lipo-oligosaccharide (LOS) and core oligosaccharides. This revealed that some MAMPs have additive (e.g. flg22 with elf18) and even synergistic (flg22 and LOS) effects, whereas others mutually interfere (flg22 with OGA). OGA suppression of flg22-induced defences was not a result of the interference with the binding of flg22 to its receptor flagellin-sensitive 2 (FLS2). MAMPs induce different calcium influx signatures, but these are concentration dependent and unlikely to explain the differential induction of defence genes [pathogenesis-related gene 1 (PR1), plant defensin gene 1.2 (PDF1.2) and phenylalanine ammonia lyase gene 1 (PAL1)] by flg22, elf18 and OGA. The peptide MAMPs are potent elicitors at subnanomolar levels, whereas PGN and LOS at high concentrations induce low and late host responses. This difference might be a result of the restricted access by plant cell walls of MAMPs to their putative cellular receptors. flg22 is restricted by ionic effects, yet rapidly permeates a cell wall matrix, whereas LOS, which forms supramolecular aggregates, is severely constrained, presumably by molecular sieving. Thus, MAMPs can interact with each other, whether directly or indirectly, and with the host wall matrix. These phenomena, which have not been considered in detail previously, are likely to influence the speed, magnitude, versatility and composition of plant defences.

Ultrastructural observations on Puccinia menthae infections.

Haustoria and associated regions of the hostpathogen interfaces of the autoecious rust Puccinia menthae, during mono- and dikariotic phases of development on its host Mentha spicata, differed in ultrastructural and cytochemical features. By application of the PA-TCH-SP procedure, polysaccharides were shown not only to be major constituents of the walls of intercellular hyphae, haustorial mother cells (HMC) and haustoria of both the monokaryon and dikaryon (m- and dhaustoria, respectively) of P. menthae, but were also present within the extra-haustorial matrix (EM) of both types of haustoria. In the neck region of d-haustoria, which is structurally more differentiated than in m-haustoria, there was evidence for the presence of lipopolysaccharides and glycoprotein. However, the characteristic neck-band, which stains densely in conventional staining of the d-haustorium, did not react with PA-TCH-SP. The outermost layer of the dikaryotic HMC wall was completely digested by protease, whereas treatment with protease and cellulase did not affect either mono- or dikariotic intercellular hyphae or walls of m-haustoria, although these treatments indicated the presence of protein and cellulose in the EM. In dikaryotic infections, protein was found to be a major constituent of the EM. Cellulase treatment resulted in almost complete digestion of the host wall, except for a thin outer layer, whereas hyphal and haustorial walls were unaffected. The morphology and structural differences observed between the mono- and dikaryotic infection structures of P. menthae, and their interactions with host cells were clarified, and confirmed the possibility of their functional differences. Such information should facilitate further comparative studies on host-parasite interfaces at different stages of the rust life cycle and other biotrophic fungi.

An attempt to determine the age of geological fractures by applying Rb-Sr mineral isochron dating to fracture-filling minerals

Geological fractures commonly contain the minerals calcite and zeolite, which have crystallized in the fracture after its formation. The minimum age of formation of the fracture can be estimated from the age of the fracture-filling minerals. We tried to determine the age of fracturing by applying the Rb‐Sr mineral isochron method to the fracture-filling paragenetic calcite and zeolite samples from fractures in the Kurihashi granodiorite and a skarn in the Kamaishi mine in northeastern Japan. The age of crystallization of fracture-filling minerals was estimated to be in the range 74 to 58 Ma in the Kurihashi granodiorite. The main causes of fracturing were considered to be igneous activities and the cooling of magma. We could not determine ages for some of the fractures we investigated, probably because of the subsequent low-temperature alteration after fracturing, or because of host wall rock contamination of the fracture-filling mineral samples. The ages determined for fractures in the skarn pre-dated the skarnization process. It is possible that these fractures formed before the skarnization. However, selective leaching of rubidium during skarnization reduces the Rb/Sr ratio. Therefore, skarnization can have the effect of producing erroneously old Rb‐Sr ages. From the initial 87 Sr/ 86 Sr ratios, we determined changes in the strontium isotopic ratio in the local groundwater from the Late Cretaceous through the Paleocene, noting a significant increase at 62 Ma.

Basidiomycetous endophytes in jungermannialean (leafy) liverworts have novel cytology and species-specific host ranges: a cytological and experimental study

This article reviews published data on the likely occurrence of basidiomycetous endophytes in jungermannialean (leafy) liverworts and presents a new overview based on observations on freshly collected specimens supplemented with confirmation, by transmission electron microscopy, of dolipore septa in representative taxa. These associations are widespread in the Lophoziaceae and Arnelliaceae and sporadic in the Jungermanniaceae, Scapaniaceae, and Geocalycaceae. They are almost exclusively confined to taxa growing on well-drained, humus-rich substrata and are absent from epiphytes and species from bare rocks and waterlogged habitats. Cross-infection experiments between axenically cultured liverworts ( Lophozia , Nardia , Diplophyllum , Southbya , and Aneura in the Metzgeriales) and their mycobionts revealed the associations to be host specific, in striking contrast with the wide host ranges previously recorded for rhizoidal ascomycetes in the Cephaloziaceae and other families. More vigorous growth of resynthesized basidiomycete associations compared with their axenic counterparts is indicative of nutritional benefits to the liverworts. The fungi enter their hosts via the tips of the rhizoids and develop distinctive distributions within the liverwort stem. In the Arnelliaceae, this comprises a central medullary strand; in the Lophoziaceae and Scapaniaceae, the ventral medulla contains a mosaic of infected and noninfected cells. In the latter, pegs of host wall material overgrow penetrating hyphae. Electron microscopy revealed that all of the endophytes have straight imperforate parenthesomes typical of heterobasidiomycetes. The fungi form hyphal coils that outlive the host cytoplasm, and digestion of the mycobionts, as seen in Aneuraceae and orchidaceous mycorrhizas, are absent. Closely similar mosaic infection patterns in Lophoziaceae and Scapaniaceae strenghten the link between the two families based on molecular data, but the present cross-infection and ultrastructural data indicate that the Calypogeia endophyte is ascomycetous rather than a member of the Sebacinaceae as reported previously. The distribution of basidiomycete associations in liverworts suggests that these probably arose several times and are more recent in origin than associations with glomeromycotean fungi.

Histopathology of Fusarium wilt of staghorn sumac (Rhus typhina) caused by Fusarium oxysporum f. sp. callistephi race 3. I. Modes of tissue colonization and pathogen peculiarities

Light and transmission electron microscope studies of naturally infected or inoculated staghorn sumac plants by Fusarium oxysporum f. sp. callistephi race 3 are reported. Diverse extrinsic material (including latex in some instances) or elements occurred in vessel lumina. Some of this material labelled for pectin, often in association with tyloses, as did other opaque matter in paratracheal cells, related to alterations of their protective layer. Pronounced alterations of pit membranes of bordered pits occurred, with their outer portions disrupted into bodies of opaque matter, strongly labelled for cellulose, and their middle portions as unlabelled shreds. Similarly labelled opaque bodies occasionally occurred on vessel walls and lumina. Direct penetration of host cell secondary walls by the pathogen occurred, but these were degraded to any extent only following intramural invasion. Vessel walls, at all stages of infection, were lined with variously structured matter: in their thinnest forms, by single or paired, equidistant or widely spaced opaque bands, and in their thickest forms as alternating opaque and less opaque layers. Other thin elements, often enclosing opaque material, vesicular structures, or occasionally particles of ribosomal appearance were also delineated by similar but frequently infolded bands. These elements were sometimes observed to be confluent with fungal cells and to label for chitin. Many fungal elements were bound by only a thin or defective lucent wall layer, practically unlabelled for chitin, or by a locally thickened, labelled one; labelling for this substrate was also frequently associated with the fungal cell outer opaque wall layer or with some outer extracellular matter. Fine filamentous structures, connected to fungal cells, to the vessel lining matter, and to these other elements, extended into host walls. The lining itself generally did not label for cellulose or chitin. These observations are discussed in comparison with similar observations made regarding other wilt diseases that we have studied.