Glomeromycotean associations in liverworts: a molecular, cellular, and taxonomic analysis

Liverworts form endophytic associations with fungi that mirror mycorrhizal associations in tracheophytes. Here we report a worldwide survey of liverwort associations with glomeromycotean fungi (GAs), together with a comparative molecular and cellular analysis in representative species. Liverwort GAs are circumscribed by a basal assemblage embracing the Haplomitriopsida, the Marchantiopsida (except a few mostly derived clades), and part of the Metzgeriidae. Fungal endophytes from Haplomitrium, Conocephalum, Fossombronia, and Pellia were related to Glomus Group A, while the endophyte from Monoclea was related to Acaulospora. An isolate of G. mosseae colonized axenic thalli of Conocephalum, producing an association similar to that in the wild. Fungal colonization in marchantialean liverworts suppressed cell wall autofluorescence and elicited the deposition of a new wall layer that specifically bound the monoclonal antibody CCRC-M1 against fucosylated side groups associated with xyloglucan and rhamnogalacturonan I. The interfacial material covering the intracellular fungus contained the same epitopes present in host cell walls. The taxonomic distribution and cytology of liverwort GAs suggest an ancient origin and multiple more recent losses, but the occurence in widely separated liverwort taxa of fungi related to glomeromycotean lineages that form arbuscular mycorrhizas in tracheophytes, notably the Glomus Group A, is better explained by host shifting from tracheophytes to liverworts.     

DICROGLOSSUM CRISPATULUM GEN. ET COMB. NOV. FROM WESTERN AUSTRALIA,REPRESENTING A NEW TRIBE WITHIN THE DELESSERIACEAE (RHODOPHYTA)1

Dicroglossum gen. nov. (Delesseriaceae, Ceramiales) is a monotypic genus based on Delesseria crispatula, a species originally described by Harvey for plants collected from southwestern Western Australia. Distinctive features of the new genus include exogenous indeterminate branches; growth by means of a single transversely dividing, apical cell; absence of intercalary divisions in the primary, secondary, and tertiary cell rows; lateral pericentral cells not transversely divided; not all cells of the secondary cell rows producing tertiary cells rows; all tertiary initials reaching the thallus margin; midrib present but lateral nerves absent; determinate lateral bladelets arising endogenously; blades monostromatic, except, at the midrib; carpogonial branches restricted to primary cell rows, on both surfaces of unmodified blades; procarps produced on both blade surfaces, each procarp consisting of a supporting cell that bears two four-celled carpogonial branches and one sterile-cell group of three to four cells; and tetrasporangia borne in two layers, separated by a central row of sterile cells. The combination of exogenous indeterminate branching and bicarpogonial procarps is considered to warrant the recognition of a new tribe, the Dicroglosseae, within the subfamily Delesserioideae.     

Caecomyces sympodialis sp. nov., a new rumen fungus isolated from Bos indicus

A new anaerobic rumen fungus was isolated from the rumen fluid of a yellow cow (Bos indicus). This fungus appears to be a previously undescribed species of the genus Caecomyces, it possessing uniflagellate zoospores, a spherical holdfast, tubular sporangiophores and bulbous rhizoids. This new fungus also features distinctive multisporangiate thallus sympodially distributed on sporangiophores. The fungus resembles Caecomyces communis and C. equi in that it characterizes bulbous rhizoids and uniflagellate zoospores but differs from C. communis and C. equi in that it possesses multisporangiate and sympodial sporangia. This new fungus and Cyllamyces aberensis both reveal similar morphology during early thallus development in having a spherical holdfast, but they vary from unbranched sporangiophores and additional bulbous rhizoids. In addition, the molecular phylogenetic analyses ITS1 (internal transcribed spacer 1) also conform to the results of the morphological examinations of Caecomyces. For the mentioned reasons, this new species of fungus is described as Caecomyces sympodialis sp. nov. The genera of Neocallimasticaceae and species of Caecomyces are also keyed out.     

Characterization of enzymatic antioxidants in the lichen Ramalina lacera and their response to rehydration

Lichens are slow-growing associations of fungi and green algae or cyanobacteria. This symbiotic association forms a common thallus that does not possess roots or a waxy cuticle and depends mainly on atmospheric input of mineral nutrients. The lifestyle of most lichens is composed of alternating periods of desiccation with low metabolic activity and hydration that induces increase in their metabolism. We have previously shown that rehydration of the naturally desiccated lichen Ramalina lacera resulted in a rapid increase in photosynthesis and was accompanied by a burst of intracellular production of reactive oxygen species and nitric oxide, as well as a transient decrease in water-soluble antioxidant capacity. We report here on enzymatic antioxidants of R. lacera and their response to rehydration. Native gel electrophoresis of crude extracts of R. lacera stained for superoxide dismutase (SOD) activity revealed four Fe-SOD and four Mn-SOD electromorphs that are synthesized by the alga, a Cu/Zn-SOD and a Mn-SOD that are the product of the fungus, and two catalases synthesized one by the fungus and the other by the algae. In addition, we detected glutathione reductase and glucose-6-phosphate dehydrogenase activities in crude extracts of R. lacera. Rehydration of the thalli resulted in a decrease in SOD activity of all forms, and a transient decrease in total catalase activity, as well as a decrease in the antioxidant auxiliary enzymes glutathione reductase and glucose-6-phosphate dehydrogenase.     

Anaeromyces mucronatus nov. gen., nov. sp. A new strictly anaerobic rumen fungus with polycentric thallus

A new species of strictly anaerobic fungus was isolated from the cow rumen. It is characterized by a polycentric thallus, a polynuclear rhizomycelium, mucronate zoosporangia and uniflagellated zoospores. It is also singular in that the sporocysts do not react to the specific lectins of L-fucose, N-acetyl-D-galactosamine and diacetyl chitobiose. These characteristics justify the creation of a new genus.     

Drachiella liaoii sp. nov., a new member of the Schizoserideae (Delesseriaceae,Rhodophyta) from Taiwan and the Philippines

A new member of Delesseriaceae (Ceramiales, Rhodophyta) is described from Southern Taiwan and the Philippines. On the basis of comparative vegetative and reproductive morphology, and phylogenetic analysis inferred from nuclear-encoded large-subunit ribosomal DNA sequences (LSU rDNA), we conclude that it belongs in the genus Drachiella, tribe Schizoserideae, subfamily Phycodryoideae. The new taxon shares with other Drachiella species the absence of macro- and microscopic veins; diffuse growth by marginal and intercalary meristematic cells; a polystromatic, lobed thallus; abundance of rhizoidal marginal proliferations used for attachment; convoluted plastids in surface cells; abundant secondary pit connections among adjacent vegetative cells; large intercellular spaces between surface cells; procarps confined to the upper side of the thallus, circular in outline, consisting of a supporting cell bearing a strongly curved carpogonial branch and two sterile groups that remain undivided; vertical division of gonimoblast initial from auxiliary cell, and unilateral, monopodial branching of gonimoblasts; and mature cystocarps with a massive candelabrum-like fusion cell of fused gonimoblasts bearing carposporangia in branched chains. It is distinguished from the other members of the genus by thalli that consist of extensive tangled mats of prostrate and overlapping decumbent blades, procarps confined to the upper side of the thallus, and the lack of basal stalks or stipes. Whereas the Schizoserideae is predominantly a Southern Ocean tribe, one of the tribe's four genera, Drachiella, was known only from the eastern Atlantic and Mediterranean. We herein report the first record of the genus for the Indo-Pacific Ocean, and describe Drachiella liaoii, sp. nov., as a fourth species in the genus.     

CATENOPHLYCTIS,A NEW GENUS OF THE CATENARIACEAE

Catenophlyctis gen. nov. is established in the family Catenariaceae to include the fungus previously known as Phlyctorhiza variabilis Karling. This ubiquitous saprophyte was formerly included in the genus Phlyctorhiza Hanson of the Chytridiales on the grounds that its eucarpic thallus is predominantly monocentric and because it develops usually from an enlargement of the germ tube. Additional studies on this species in India have confirmed the previous observations that the thallus of some strains frequently becomes extensively polycentric and Catenaria-like. Also, its zoospores have been found to be similar in structure to those of species of the Catenariaceae. Accordingly, this species cannot be retained in Phlyctorhiza as Hanson defined the genus, and it is transferred from the Chytridiales to a new genus of the family Catenariaceae in the order Blastocladiales.     

Characterization of Enzymatic Antioxidants in the Lichen Ramalina lacera and Their Response to Rehydration

Lichens are slow-growing associations of fungi and green algae or cyanobacteria. This symbiotic association forms a common thallus that does not possess roots or a waxy cuticle and depends mainly on atmospheric input of mineral nutrients. The lifestyle of most lichens is composed of alternating periods of desiccation with low metabolic activity and hydration that induces increase in their metabolism. We have previously shown that rehydration of the naturally desiccated lichen Ramalina lacera resulted in a rapid increase in photosynthesis and was accompanied by a burst of intracellular production of reactive oxygen species and nitric oxide, as well as a transient decrease in water-soluble antioxidant capacity. We report here on enzymatic antioxidants of R. lacera and their response to rehydration. Native gel electrophoresis of crude extracts of R. lacera stained for superoxide dismutase (SOD) activity revealed four Fe-SOD and four Mn-SOD electromorphs that are synthesized by the alga, a Cu/Zn-SOD and a Mn-SOD that are the product of the fungus, and two catalases synthesized one by the fungus and the other by the algae. In addition, we detected glutathione reductase and glucose-6-phosphate dehydrogenase activities in crude extracts of R. lacera. Rehydration of the thalli resulted in a decrease in SOD activity of all forms, and a transient decrease in total catalase activity, as well as a decrease in the antioxidant auxiliary enzymes glutathione reductase and glucose-6-phosphate dehydrogenase.     

An unusual microfungus in a fungal spore from the Lower Devonian Rhynie chert

Abstract: A new fossil microfungus, Kryphiomyces catenulatus gen. et sp. nov., occurs as an endobiotic mycelial thallus in a large spore of a glomeromycotan fungus from the Lower Devonian Rhynie chert. The thallus consists of branched (?pseudo‐)septate hyphae with numerous catenulate swellings. Some hyphal tips produce spherical reproductive structures or propagules. Hyphal morphology in K. catenulatus is reminiscent of that in certain extant Hyphochytridiomycota, Chytridiomycota, and even Ascomycota, but specific diagnostic features that allow assignment of the fossil to modern groups are absent. The discovery of this interfungal association broadens our knowledge about the diversity of microfungi and their intricate associations in early continental ecosystems.     

Starting from scratch: Evolution of the lichen thallus in the basidiolichen Dictyonema (Agaricales: Hygrophoraceae)

Phylogenetic studies indicate that the basidiolichen genus Dictyonema s.lat., often thought to represent only a single genus with few species, includes several well-supported genus-level clades, all of which form associations with a unique lineage of obligately lichenized cyanobacteria (Rhizonema). In an attempt to elucidate the evolution and genus- and species-level diversification in Dictyonema s.lat., we generated 68 new sequences of the nuclear large subunit rDNA (nuLSU), the internal transcribed spacer (ITS), and the RNA polymerase II subunit (RPB2), for 29 species-level lineages representing all major clades of Dictyonema s.lat. and most of the species currently known. The multilocus phylogeny obtained via maximum likelihood and Bayesian approaches indicates the presence of five genus-level groups: a basal clade, Cyphellostereum, that is sister to the rest of the species, a paraphyletic grade representing Dictyonema s.str., and three clades representing the genera Acantholichen, Cora, and Corella. To determine the evolutionary transformations of the lichenized thallus in the group, ancestral character state reconstruction was done using six characters (lichenisation, thallus type, cortex type, hyphal sheath and haustorial type, photobiont morphology, and basidiocarp type). Our analysis indicates a progressive development of the lichenized thallus from loosely organized filamentous crusts with separate, cyphelloid basidiocarps in Cyphellostereum, to filamentous crusts with derived hyphal sheath and cyphelloid–stereoid basidiocarps partially incorporated into the lichen thallus in Dictyonema, to squamulose–foliose thalli with corticioid basidiocarps entirely supported by the lichen thallus in Cora. These results indicate a remarkable evolutionary integration of lichenized and reproductive tissues in Dictyonema s.lat., supporting the hypothesis that, at least in this case, lichenized thalli may have evolved from reproductive structures in their nonlichenized ancestors.     

The placenta in Monoclea forsteri Hook. and Treubia lacunosa (Col.) Prosk: insights into placental evolution in liverworts

Placental morphology is remarkably diverse between major bryophyte groups, especially with regard to the presence and distribution of transfer cells in the sporophyte and gametophyte. In contrast, with the exception of metzgerialean liverworts, placental morphology is highly conserved within major bryophyte groups. Here we examine the ultrastructure of the placenta in Monoclea forsteri and Treubia lacunosa, basal members of the marchantialean and metzgerialean liverwort lineages, respectively. In both species several layers of transfer cells are found on both sides of the placenta, with sporophytic transfer cells exhibiting prominent wall labyrinths. Consistent with previous reports of a similar placenta in other putatively basal and isolated liverwort genera such as Fossombronia, Haplomitrium, Blasia and Sphaerocarpos, this finding suggests that this type of placenta represents the plesiomorphic (primitive) condition in liverworts. Distinctive ultrastructural features of placental cells in Monoclea include branched plasmodesmata in the sporophyte and prominent arrays of smooth endoplasmic reticulum, seemingly active in secretion in the gametophyte. These arrays contain a core of narrow tubules interconnected by electron-opaque rods, structures with no precedent in plants. Analysis of the distribution of different types of placenta in major bryophyte groups provides valuable insights into their inter-relationships and possible phylogeny.     

Thallus Differentiation in the Marchantialean Liverwort Asterella wilmsii (Steph.) with Particular Reference to Longitudinal Arrays of Endoplasmic Microtubules in the Inner Cells

This light and electron microscope study of the liverwort Asterellareveals that, as in other Marchantiales, the cells lining thedorsal air chambers are highly vacuolate with numerous amylochloroplastsin the peripheral cytoplasm. The ventral parenchyma in the midribof the thallus contains aseptate fungal hyphae surrounded byan interfacial matrix and host cytoplasm forming transvacuolarstrands. These are lined with microtubules, rarely seen in otherfungal-hepatic associations or in mycorrhizas. Numerous lipidbodies found in all the thallus cells are thought to be associatedwith perennation during the winter dry season. Elongated, thick walled inner thallus cells, between the dorsalair chambers and the fungus-containing tissue, have a cytologicalorganization not previously recorded in land plants. Initiallyhighly vacuolate, with numerous microtubules of random orientationlining the tonoplast, these cells subsequently show interdigitationof vacuoles and cytoplasm producing a labyrinth of sphericaland elongate tonoplast profiles lined by longitudinal arraysof microtubules. At the same time the cytoplasm becomes increasinglyelectron-lucent and the ribosomes, progressively lost from theER, clump together. At maturity the inner thallus cells arehighly polarized with most of the vacuoles lying nearer thethallus apex. In pits in the end walls, numerous plasmodesmata,with expanded cytoplasmic annuli recall the plamodesmatal fieldsin the mesophyll and phloem of the leaves in vascular plants. Far from being supporting parenchyma or sclerenchyma as assumedhitherto, the inner thallus cells of Asterella are clearly highlydifferentiated. Their vacuole microtubule associations are highlysuggestive of a microtubule-based translocation system akinto that seen in many animal cells and perhaps fungal hyphae,but very different from bulk flow in sieve elements and actin-basedcytoplasmic streaming.Copyright 1994, 1999 Academic Press Cytoskeleton, liverwort, microtubules, plasmodesmata, solute transport     

藻苔纲Takakiopsida，一个独特的苔藓植物类群

藻苔属Takakia在建立之初被认为是原始的苔类植物。这一神秘类群的出现引起了苔藓学家的兴趣,发表了一系列相关的论文。但是随着其孢子体的发现,它的系统位置引起了争论。本文详细分析了藻苔属植物的形态性状特征,参考了大量其他学科的研究成果,认为它既不能归于类,也不能归于苔类。就其系统位置而言,应该成为一独立的纲——藻苔纲。     

THALASSOCHYTRIUM GRACILARIOPSIDIS (CHYTRIDIOMYCOTA), GEN. ET SP. NOV., ENDOSYMBIOTIC IN GRACILARIOPSIS SP. (RHODOPHYCEAE)

Thalassochytrium gracilariopsidis gen. et sp. nov. is an endosymbiotic, polycentric, zoosporic fungus that infected cultures of the red alga Gracilariopsis sp. Based on the posteriorly uniflagellate zoospore and the platelike cristae of the mitochondria, the fungus is placed in the Chytridiomycota. Ultrastructurally, the fungal zoospore is distinguished by the anterior position of the kinetosome, a unique microbody-lipid globule complex, an electron-opaque helix associated with the kinetosome and lipid globules, and a beaked nucleus. Zoospores are positively phototactic, and the unusual helix might constitute part of the photosensory apparatus. Zoospores lack certain taxonomically important structures, such as a rumposome, props, a nonflagellated kinetosome, and flagellar roots. The organism does not fit into any described genus, and the features of its zoospore differ from those of any described order. The fungal thallus is polycentric with multinucleate, septate hyphae. Haustoria form within the algal cells. The fungus does not appear to cause major harm to its host and seems to be host specific. However, during intense sporulation of the fungus, degradation of host chloroplasts was observed in medullary cells.     

Water Storage in the Lichen Family Umbilicariaceae

Quantitative relationships between thallus structure and water storage and retention capacities In 12 species of the lichen family Umbilicariaceae were explored using three recent techniques for plant structure analysis: stereology (3D quantification of microscopic Images), mercury Intrusion porosimetry (determination of pore size distribution of tissues) and low-temperature scanning electron microscopy (LTSEM). Water storage capacity of the thallus was related neither to thallus density nor surface area of the thallus; It was directly related to the total porosity of the thallus and inversely related to the proportion of thallus volume occupied by cell walls and gelatinous substances. Water retention capacity increased with increasing thallus density and was decreased by slight increases in the surface area of the upper side of the thallus. Water storage and retention capacities exhibited a positive correlation only when the storage capacity was expressed on a surface area basis. LTSEM study of fully hydrated specimens revealed that many intercellular spaces of the upper cortex and upper parts of the algal layer contained liquid water. Intercellular spaces of the lower part of the algal layer and medulla were in general either airfilled or partially occupied by gelatinous substances. Species with rhizinomorphs and substrate-hygrophytic (water uptake from surface run-offs) stored more water and retained it longer than aerohygrophytic species (water uptake from the atmosphere) lacking rhizinomorphs. Thallus structure of aerohygrophytic species seems to facilitate rapid gas exchange with the environment, improving water uptake and carbon gain when atmospheric moisture is available but accelerating dehydration when the atmosphere becomes dry.     

Studies on the root associations of the truffle Terfezia terfezioides

The paper contains an overview of the results of the studies made on the truffle Terfezia terfezioides, particularly the investigations related to the associations of this fungus with plants. Twelve plant species originated from a natural habitat of the fungus were supposed to be connected with T. terfezioides based on the anatomy of the endogenous fungal structures in their roots. Aseptic experiments were carried out on modified MMN substrates with different phosphate concentrations to study the interaction of T. terfezioides with Robinia pseudoacacia and Helianthemum ovatum. The colonization of the roots of black locust was always weaker than that of Helianthemum. The main characteristics were the intracellular coiled, branched, frequently septated hyphae in dead root cells. The intercellular hyphae formed Hartig-net with finger like structures only in Helianthemum, the interactions could not be considered unambiguously as mycorrhizae. There was no difference between the RFLP profiles of the nr DNA ITS of nineteen fruit bodies collected at the same time from the habitat and the ITS of three randomly chosen specimens were identical on sequence level, too. These invariability makes to design species specific PCR primers possible to check unambiguously the host plants.     

Fluctuations in the concentration of extracellular ATP synchronized with intracellular Ca(2+) oscillatory rhythm in cultured cardiac myocytes

Isolated and cultured neonatal cardiac myocytes contract spontaneously and cyclically. The intracellular concentration of free Ca²⁺ also changes rhythmically in association with the rhythmic contraction of myocytes (Ca²⁺ oscillation). Both the contraction and Ca²⁺ oscillatory rhythms are synchronized among myocytes, and intercellular communication via gap junctions has been considered primarily responsible for the synchronization. However, a recent study has demonstrated that intercellular communication via extracellular ATP-purinoceptor signaling is also involved in the intercellular synchronization of intracellular Ca²⁺ oscillation. In this study, we aim to elucidate whether the concentration of extracellular ATP changes cyclically and contributes to the intercellular synchronization of Ca²⁺ oscillation among myocytes. In almost all the cultured cardiac myocytes at four days in vitro (4 DIV), intracellular Ca²⁺ oscillations were synchronized with each other. The simultaneous measurement of the concentration of extracellular ATP and intracellular Ca²⁺ revealed the extracellular concentration of ATP actually oscillated concurrently with the intracellular Ca²⁺ oscillation. In addition, power spectrum and cross-correlation analyses suggested that the treatment of cultured cardiac myocytes with suramin, a blocker of P2 purinoceptors, resulted in the asynchronization of Ca²⁺ oscillatory rhythms among cardiac myocytes. Treatment with suramin also resulted in a significant decrease in the amplitudes of the cyclic changes in both intracellular Ca²⁺ and extracellular ATP. Taken together, the present study demonstrated the possibility that the concentration of extracellular ATP changes cyclically in association with intracellular Ca²⁺, contributing to the intercellular synchronization of Ca²⁺ oscillation among cultured cardiac myocytes.     

Phylogenetic relationships in Termitomyces (Family Agaricaceae) based on the nucleotide sequence of ITS: a first approach to elucidate the evolutionary history of the symbiosis between fungus-growing termites and their fungi

Termitomyces constitutes a very poorly known genus of fungi whose essential characteristic is that all representatives of the genus are cultivated by termites (Macrotermitinae) in their nest and that all the fungi cultivated by termites belong to this genus. For the first time, the phylogenetic relationships of several African Termitomyces species was studied by the sequencing of their internal transcriber spacer region (ITS1--5.8S--ITS2). It appeared that this group is clearly monophyletic and belongs to the Tricholomataceae family. The total homology of the ITS zone of several Termitomyces symbionts of different termite genera indicated that the specific diversity of this group is in fact less important than previously supposed. Finally, the comparison between the Termitomyces phylogenetic tree and the taxonomic tree of Macrotermitinae showed that if for certain genera the hypothesis of termite/fungus coevolution is acceptable, it should not be applied for all symbiosis.     

Electron microscopic study of the lichenDermatocarpon hepaticum (Ach.) Th. Fr.

Summary The ultrastructure of the alga and fungus of the lichenDermatocarpon hepaticum and their relationship has been studied. The contact between the symbionts was found to be of a different type from that found in other lichen species, and to some extent comparable with the relation of obligate parasites and their host.The anatomy of the thallus and the distribution pattern of the components in the thallus has been revealed by examining serial sections.     

Zhutheca Liu, Li et Hilton gen. nov., the fertile pinnules of Fascipteris densata Gu et Zhi and their significance in marattialean evolution

The morphology of the fertile pinnules of Fascipteris densata Gu et Zhi have been subjected to a detailed morphological investigation based on recently collected specimens from the Upper Permian of Yunnan Province, south China. These investigations have revealed that this species possesses synangia of the Asterotheca-type, situated in two or three rows either side of the midrib on a Fascipteris-type pinnule. This arrangement of Asterotheca-type synangia is extremely unusual considering that all other reports of this genus are with a single row of synangia located on each side of the midrib of a pecopteroid-type pinnule. As a consequence of this unique morphological arrangement, a new genus, Zhutheca densata Liu, Li et Hilton gen. et comb. nov. has been created to distinguish this material from other specimens of the Asterotheca and Fascipteris types. The structure and arrangement of the fertile pinnule of Zhutheca are compared with other Palaeozoic and Mesozoic marattialean taxa with which it shares certain features of its morphology. In addition, the stratigraphic, evolutionary and phylogenetic significance of Zhutheca are considered in detail.