Spore Sac Research Articles

Diversity of Neotropical stalked-puffball: Two new species of Tulostoma with reticulated spores

Species of the genus Tulostoma are easily recognizable by the presence of a spore sac, with a mouth from which spores are released, attached to a stipe. Tulostoma is a species-diverse genus with a worldwide distribution, and some attempts were made to delimitate species and to evaluate reliable taxonomic-informative characteristics for species identification. However, there is a notable information gap regarding Neotropical species, especially for geographic distribution and DNA data, which hampers further understanding of the infrageneric diversity, evolution, and ecology of this genus. Based on morphological analysis, molecular phylogenetics and geographic distribution, we propose here two new species of Tulostoma with reticulated spores, from the two threatened Brazilian geographical areas, Atlantic Forest and “campos rupestres” (rupestrian grassland), as well as we provide notes on the taxonomic rank of Tulostoma exasperatum var. ridleyi.

Sporogenesis in Physcomitrium patens: Intergenerational collaboration and the development of the spore wall and aperture.

Although the evolution of spores was critical to the diversification of plants on land, sporogenesis is incompletely characterized for model plants such as Physcomitrium patens. In this study, the complete process of P. patens sporogenesis is detailed from capsule expansion to mature spore formation, with emphasis on the construction of the complex spore wall and proximal aperture. Both diploid (sporophytic) and haploid (spores) cells contribute to the development and maturation of spores. During capsule expansion, the diploid cells of the capsule, including spore mother cells (SMCs), inner capsule wall layer (spore sac), and columella, contribute a locular fibrillar matrix that contains the machinery and nutrients for spore ontogeny. Nascent spores are enclosed in a second matrix that is surrounded by a thin SMC wall and suspended in the locular material. As they expand and separate, a band of exine is produced external to a thin foundation layer of tripartite lamellae. Dense globules assemble evenly throughout the locule, and these are incorporated progressively onto the spore surface to form the perine external to the exine. On the distal spore surface, the intine forms internally, while the spiny perine ornamentation is assembled. The exine is at least partially extrasporal in origin, while the perine is derived exclusively from outside the spore. Across the proximal surface of the polar spores, an aperture begins formation at the onset of spore development and consists of an expanded intine, an annulus, and a central pad with radiating fibers. This complex aperture is elastic and enables the proximal spore surface to cycle between being compressed (concave) and expanded (rounded). In addition to providing a site for water intake and germination, the elastic aperture is likely involved in desiccation tolerance. Based on the current phylogenies, the ancestral plant spore contained an aperture, exine, intine, and perine. The reductive evolution of liverwort and hornwort spores entailed the loss of perine in both groups and the aperture in liverworts. This research serves as the foundation for comparisons with other plant groups and for future studies of the developmental genetics and evolution of spores across plants.

REPORT OF A BRYOPHYTIC CAPSULE FROM THE DECCAN INTERTRAPPEAN SERIES OF MADHYA PRADESH, INDIA.

A sporophyte measure 5.5 mm long and shows a short, slender seta and an oval erect, capsule. A smooth, hood shaped calyptra covers the top. It contains ten spore sacs (spore chambers) in longitudinal section. The spore sacs measures are 1.7 mm long and 300 to 500 µm in diameter are separated by parenchymatous septae. The apophysis is poorly differentiated. The operculum is seen as an outline. Columella and peristomial teeth are lacking. Spore and spores tetrad are surrounded by pseudo-elaters. The spores are meiogenous, arranged in tetrahedral tetrads. The seta is short and slender. The calyptra is hood-shaped. As it shows close similarities with Krempogonium mohgaonensis (Nambudiri, Chitaley & Yawale, 2004) it is kept under the genus Krempogonium as a new species Krempogonium deccanii sp.nov.

Molecular phylogeny and new light microscopic data of Metchnikovella spiralis (Microsporidia: Metchnikovellidae), a hyperparasite of eugregarine Polyrhabdina sp. from the polychaete Pygospio elegans.

Metchnikovellids are a deep-branching group of microsporidia, parasites of gregarines inhabiting the alimentary tract of polychaetes and some other invertebrates. The diversity and phylogeny of these hyperparasites remain poorly studied. Modern descriptions and molecular data are still lacking for many species. The results of a light microscopy study and molecular data for Metchnikovella spiralis Sokolova et al., 2014, a hyperparasite of the eugregarine Polyrhabdina sp., isolated from the polychaete Pygospio elegans, were obtained. The original description of M. spiralis was based primarily on the analysis of stained preparations and transmission electron microscopy images. Here, the species description was complemented with the results of in vivo observations and phylogenetic analysis based on the SSU rRNA gene. It was shown that in this species, free sporogony precedes sac-bound sporogony, as it occurs in the life cycle of most other metchnikovellids. Spore sacs are entwined with spirally wound cords, and possess only one polar plug. Phylogenetic analyses did not group M. spiralis with M. incurvata, another metchnikovellid from the same gregarine species, but placed it as a sister branch to Amphiacantha. The paraphyletic nature of the genus Metchnikovella was discussed. The taxonomic summary for M. spiralis was emended.

Comparative transcriptomics and host-specific parasite gene expression profiles inform on drivers of proliferative kidney disease

The myxozoan parasite, Tetracapsuloidesbryosalmonae has a two-host life cycle alternating between freshwater bryozoans and salmonid fish. Infected fish can develop Proliferative Kidney Disease, characterised by a gross lymphoid-driven kidney pathology in wild and farmed salmonids. To facilitate an in-depth understanding of T.bryosalmonae-host interactions, we have used a two-host parasite transcriptome sequencing approach in generating two parasite transcriptome assemblies; the first derived from parasite spore sacs isolated from infected bryozoans and the second from infected fish kidney tissues. This approach was adopted to minimize host contamination in the absence of a complete T.bryosalmonae genome. Parasite contigs common to both infected hosts (the intersect transcriptome; 7362 contigs) were typically AT-rich (60–75% AT). 5432 contigs within the intersect were annotated. 1930 unannotated contigs encoded for unknown transcripts. We have focused on transcripts encoding proteins involved in; nutrient acquisition, host–parasite interactions, development, cell-to-cell communication and proteins of unknown function, establishing their potential importance in each host by RT-qPCR. Host-specific expression profiles were evident, particularly in transcripts encoding proteases and proteins involved in lipid metabolism, cell adhesion, and development. We confirm for the first time the presence of homeobox proteins and a frizzled homologue in myxozoan parasites. The novel insights into myxozoan biology that this study reveals will help to focus research in developing future disease control strategies.

With Over 60 Independent Losses, Stomata Are Expendable in Mosses.

Because stomata in bryophytes are uniquely located on sporangia, the physiological and evolutionary constraints placed on bryophyte stomata are fundamentally different from those on leaves of tracheophytes. Although losses of stomata have been documented in mosses, the extent to which this evolutionary process occurred remains relatively unexplored. We initiated this study by plotting the known occurrences of stomata loss and numbers per capsule on the most recent moss phylogeny. From this, we identified 40 families and 74 genera that lack stomata, of which at least 63 are independent losses. No trends in stomata losses or numbers are evident in any direction across moss diversity. Extant taxa in early divergent moss lineages either lack stomata or produce pseudostomata that do not form pores. The earliest land plant macrofossils from 400 ma exhibit similar sporangial morphologies and stomatal distribution to extant mosses, suggesting that the earliest mosses may have possessed and lost stomata as is common in the group. To understand why stomata are expendable in mosses, we conducted comparative anatomical studies on a range of mosses with and without stomata. We compared the anatomy of stomate and astomate taxa and the development of intercellular spaces, including substomatal cavities, across mosses. Two types of intercellular spaces that develop differently are seen in peristomate mosses, those associated with stomata and those that surround the spore sac. Capsule architecture in astomate mosses ranges from solid in the taxa in early divergent lineages to containing an internal space that is directly connected to the conducing tissue and is involved in capsule expansion and the nourishment, hydration and development of spores. This anatomy reveals there are different architectural arrangements of tissues within moss capsules that are equally effective in accomplishing the essential processes of sporogenesis and spore dispersal. Stomata are not foundational to these processes.

Description of Metchnikovella spiralis sp. n. (Microsporidia: Metchnikovellidae), with notes on the ultrastructure of metchnikovellids.

The present paper reports results of a transmission electron microscopy study of a new metchikovellid microsporidium. It was isolated from gregarines Polyrhabdina sp. inhabiting guts of polychaetes Pygospio elegans sampled at the White Sea silt littoral zone. Free sporogony (FS) occurred in the life cycle of the microsporidium alongside sac-bound sporogony (BS). Free spores resided in a parasitophorous vacuole and were of typical metchnikovellidean structure, uninucleate and oblong. They measured on sections 2·0-3·2×1·3-1·9 μm. The life cycle included pre-sporogonial stages represented by dikaryotic cells and 4-nucleate cells with coupled nuclei. A multinucleate sporogonial plasmodium of FS split in numerous (>10) sporoblasts. In BS segregation of sporoblasts occurred within thick-walled cysts by internal budding. Spore sacs of this microsporidium, measuring on average 11·6×4·7 μm, were limited by a thick electron-dense wall, externally ornamented with spirally wound cords of dense material. These oval spore sacs contained eight barrel-shaped spores, comparable in size and ultrastructure to FS spores. Ultrastructure of both types of spores and intracellular development of the new microsporidium and Metchnikovella spp. were similar, suggesting they belong to the same genus. In this paper we describe a new species Metchnikovella spiralis and discuss morphology of metchnikovellids in the context of putative evolutionary history of Microsporidia.

Fine structure of Metchnikovella incurvata Caullery and Mesnil 1914 (microsporidia), a hyperparasite of gregarines Polyrhabdina sp. from the polychaete Pygospio elegans

Class Rudimicrosporea Sprague 1977, with its single family Metchnikovellidae, comprises hyperparasites of gregarines from the guts of marine invertebrates. Metchnikovellids remain poorly studied in spite of their significance to the evolutionary history of microsporidia; their ultrastructure and life cycles require further investigation. Here we present results of the light- and electron-microscopy study of Metchnikovella incurvata Caulleri and Mesnil 1914, isolated from lecudinid gregarines, parasitizing polychaetes Pygospio elegans in the White Sea littoral zone, and yet described only on the light-microscopic level. The life cycle of this microsporidium includes 2 sporogonies: free (FS) and sac-bound (SBS). In FS, sporonts develop into multinuclear cells (sporogonial plasmodia), which generate sporoblasts and free spores residing in direct contact with the host cytoplasm. Electron microscopy revealed their metchnikovellidean structure: a horseshoe-shaped nucleus, short manubrium perpendicular to the long axis of the spore, and a polar cap in a separate membrane container. Merogony was not observed. The earliest stages of SBS were chains of binucleate cells. They underwent a series of nuclear and cell divisions, produced extracellular envelopes, and split into boomerang-shaped spore sacs, containing up to 16 spores each. Ultrastructure and sizes of sac-bounded spores were similar to those of free-living ones. An amended diagnosis of M. incurvata is provided.

Natural Variation in CDC28 Underlies Morphological Phenotypes in an Environmental Yeast Isolate

Morphological differences among individuals in a species represent one of the most striking aspects of biology, and a primary aim of modern genetics is to uncover the molecular basis of morphological variation. In a survey of meiosis phenotypes among environmental isolates of Saccharomyces cerevisiae, we observed an unusual arrangement of meiotic spores within the spore sac in a strain from Ivory Coast, West Africa. We mined population genomic data to identify CDC28 as the major genetic determinant of meiotic and budding cell shape behaviors in this strain. Molecular genetic methods confirmed the role of the Ivory Coast variant of CDC28 in the arrangement of spores after meiosis, in the shape of budding cells in rich medium and in the morphology of filamentous growth during nitrogen limitation. Our results shed new light on the role of CDC28 in yeast cell division, and our work suggests that with the growing availability of genomic data sets in many systems, a priori prediction of functional variants will become an increasingly powerful strategy in molecular genetics.

Sacculogenesis and sporogony of Tetracapsuloides bryosalmonae (Myxozoa: Malacosporea) within the bryozoan host Fredericella sultana (Bryozoa: Phylactolaemata)

Tetracapsuloides bryosalmonae is the myxozoan parasite responsible for proliferative kidney disease (PKD) of salmonid fishes. This disease affects farmed species in North America and Western Europe where it results in significant economic losses for the rainbow trout industry. The parasite has two hosts in its life cycle, salmonid fish, and freshwater bryozoans. In this study, we describe the development of the parasite at the ultrastructural level within the bryozoan host Fredericella sultana. Single celled, presaccular stages form aggregates within the metacoel of this host which resolve into spore sacs. Within these sacs sporogenesis is initiated with the differentiation of presporogonic cells into sporogonic and valvogenic cells. These latter cells surround a sporogonic cell which subsequently divides to form a sporoplasmogenic cell and a capsulogenic cell. The capsulogenic cell divides further to form four cells each with a polar capsule, while the sporoplasmogenic cell divides resulting in four cells, two primary cells and two secondary cells. The secondary cells are engulfed by the primary cells resulting in a mature sporoplasm. It is hypothesized that autogamy occurs during the initial formation of the spore sac and that allogamy is also possible during this time.

PROLIFERATIVE, PRESACCULAR STAGES OF TETRACAPSULOIDES BRYOSALMONAE (MYXOZOA: MALACOSPOREA) WITHIN THE INVERTEBRATE HOST FREDERICELLA SULTANA (BRYOZOA: PHYLACTOLAEMATA)

Proliferative kidney disease (PKD), caused by the malacosporean parasite, Tetracapsuloides bryosalmonae, is a major disease of salmonid culture both in western Europe and North America. The fish are infected from spores that develop within freshwater bryozoans and are released into the water column. Although sporogenesis has been studied in the bryozoan host and occurs within sacs, the formation of these sacs from presaccular stages has only been hypothesized. Examination of infected bryozoans by using a range of techniques identified proliferating, presaccular amoeboid stages of T. bryosalmonae on the body wall of the bryozoan Fredericella sultana. These stages possessed unique electron-dense bodies and were observed as aggregating within the bryozoan metacoel, differentiating to form spore sacs. Spore sac growth was associated with the assimilation of the presaccular parasites rather than through cryptomitosis of sac mural cells. This sac formation through aggregation and assimilation suggests an intriguing mechanism by which T. bryosalmonae can cross-fertilize.

Development of Tetracapsuloides bryosalmonae (Myxozoa: Malacosporea) in bryozoan hosts (as examined by light microscopy) and quantitation of infective dose to rainbow trout ( Oncorhynchus mykiss)

The myxozoan parasite Tetracapsuloides bryosalmonae is the causative agent of proliferative kidney disease (PKD), a highly damaging disease of cultured salmonid fish. Within this study, phylactolaemate bryozoans were collected from a river known to be endemic for PKD and subsequently cultured in the laboratory. Sequential developmental stages of T. bryosalmonae were studied by light microscopy within the living bryozoan colonies, allowing the identification of stages attached to host peritoneum, consistent with previous molecular evidence of cryptic stages. Infection resulted in the production of large numbers of spores, which were released from the bryozoans. Experimental exposure of rainbow trout ( Oncorhynchus mykiss) to medium in which infected bryozoans were cultured resulted in clinical PKD. Rainbow trout were exposed to known numbers of T. bryosalmonae spores collected by micromanipulation, which had been released from mature spore sacs within colonies of the bryozoan Fredericella sultana. Exposure to one spore was sufficient to lead to development of PKD. These findings indicate that small numbers of bryozoans are capable of releasing sufficient spores to infect large numbers of fish, having implications for future control methods for PKD in salmonid farming.

The hyperparasitic microsporidium Amphiacantha longa Caullery et Mesnil, 1914 (Microspora: Metchnikovellidae) - description of the cytology, redescription of the species, emended diagnosis of the genus Amphiacantha and establishment of the new family Amphiacanthidae.

The ultrastructural cytology and reproduction of Amphiacantha longa Caullery et Mesnil, 1914 is described. Merogonial reproduction was not observed. The sporogony follows two lines: free disporoblastic and enveloped, polysporoblastic, involving sporoblast mother cells. The enveloped sporogony is endogenous in spore sacs of sporont origin, daughter cells are formed by vacuolation. Probably all stages have coupled nuclei. Both free and enveloped spores are equipped with an extrusion apparatus composed of a flat polar sac, a straight polar filament of manubrium type, and a posterior globular appendix. Manubrium and appendix are enclosed in a membraneous coat. Circular elements of coat material occur in the proximity of the extrusion apparatus. The membraneous coat and the surface layer of the manubrium penetrate the polar sac. The extrusion apparatus is located at the wide pole of the spore, the nuclei at the narrower pole. Hosts are gregarines of the genus Lecudina Mingazzini, living in the gut of the polychaete Lumbrinereis fragilis (O. F. Müller). The cytology and reproduction are discussed and compared to other genera of metchnikovellideans, to the chytridiopsid genera, and to microsporidia expressing the typical cytology for the group. Metchnikovellideans and chytridiopsids exhibit cytological and reproductive similarities. The species is redescribed, the diagnosis of the genus Amphiacantha Caullery et Mesnil, 1914 is emended, and the new family Amphiacanthidae, comprising the genera Amphiacantha and Amphiamblys Caullery et Mesnil, 1914, is established.

Functional Compartments During Sporangium Development in the PteridophyteCyrtomium falcatum(L. f.) Presl as Expressed in Tapetum Function

Abstract: The tapetum surrounds the developing sporogenous tissue, and therefore is suggested to have an important role during sporogerlesis. In pteridophytes details about tapetum development and function during sporangium development are poorly known. The current article analyses the leptospor-angiate development of the pteridophyte Cyrtomium falcatum in terms of functional compartmentalization related to tapetum function. Morphology, development and localization of different compounds during sporangium development are studied. Dur ing C. falcatum leptosporangiate development phases of initia tion, division, differentiation, and maturation are identified. Functional compartments are distinguished by the presence of a callose culture sac during the division and differentiation phase, and a callose spore sac during the differentiation and ma turation phase.

Functional Compartments During Sporangium Development in the Pteridophyte Cyrtomium falcatum (L.f.) Presl as Expressed in Tapetum Function

Abstract: The tapetum surrounds the developing sporogenous tissue, and therefore is suggested to have an important role during sporogerlesis. In pteridophytes details about tapetum development and function during sporangium development are poorly known. The current article analyses the leptospor‐angiate development of the pteridophyte Cyrtomium falcatum in terms of functional compartmentalization related to tapetum function. Morphology, development and localization of different compounds during sporangium development are studied. Dur ing C. falcatum leptosporangiate development phases of initia tion, division, differentiation, and maturation are identified. Functional compartments are distinguished by the presence of a callose culture sac during the division and differentiation phase, and a callose spore sac during the differentiation and ma turation phase.

Studies on the Sporogenous Lineage in the Moss Timmiella barbuloides IX. Development of the Tapetum

The ultrastructure of tapetal cells in Timmiela barbuloides was investigated in relation to events of sporogenesis. After their establishment both internally and externally to the sporogonial initials, tapetal cells enlarge and assume a permanently polarized organization after completion of meiosis. A large vacuole is formed in the cell region distal to the spore sac, the nucleus becomes centrally located, and amyloplasts lie in the cytoplasm adjacent to the spore sac. An extensive endomembrane system develops in tapetal cells during the stage of exine deposition in spore tetrads. Sheets of rough endoplasmic reticulum develop first around the nucleus then also in close proximity to the plasma membrane abutting the spore sac. Concomitantly, intervening dictyosomes produce a variety of vesicles. Unusual structures with vesicle-like profiles also occur in the inner tapetum cell walls abutting the spore sac. At the same time most of the starch is lost from the plastids in which grana-fretwork systems develop. A massive secretion of extremely electron-opaque material is associated with perine deposition onto the free spore surfaces. Degeneration of the tapetal cells during the terminal stages of spore maturation is marked by distortion of the organelles, increase in vacuolation and the appearance of electron-opaque material between the sheets of endoplasmic reticulum.

Convergence in ascospore discharge mechanism among pyrenomycete fungi based on 18S ribosomal RNA gene sequence

Fungi of the class Pyrenomycetes (Ascomycotina) form a morphological series ranging from those that shoot ascospores (sexual spores) forcibly from the ascus (spore sac) to fungi that ooze ascospores or have no obvious mechanism for ascospore release. Did forcible ascospore discharge evolve within these pyrenomycetes, or has it been lost in the group? We determined the sequences of the 18S ribosomal RNA gene from three fungi and used these, along with six sequences from our previous work and three sequences from Gen-Bank, to infer the phylogeny of 12 ascomycetes with various ascospore discharge mechanisms. The 1720 base pairs of sequence data per fungus yielded 361 variable sites, 198 phylogenetically informative sites, and a single most parsimonious tree requiring 562 nucleotide changes. The tree shows that the capacity to shoot ascospores into the air has been lost or, less probably, gained repeatedly and independently. Species lacking forcible ascospore discharge are intercalated among three lineages of species with forcible discharge. In this tree, seven of the nine internal branches appeared in 95% or more of 500 bootstrap replicates. A tree uniting the fungi with forcible ascospore discharge into a monophyletic group required 45 additional steps and fit significantly less well with the data than the most parsimonious tree, based on a maximum likelihood test. Two of the fungi whose sequence we determined, Pseudallescheria boydii and Sporothrix schenekii, are not closely related to one another, even though both are human pathogens and both are from pyrenomycete lineages lacking forcible ascospore discharge. Using the well-resolved, most parsimonious tree, we inferred base substitution patterns in the 18S rRNA. The transition-to-transversion ratio was 1.9. Of all 12 possible substitutions, 29% were from U to C. At sites corresponding to yeast stem positions, A to G transitions were frequent, perhaps compensating for some of the U to C changes, and maintaining secondary structure base pairing (A to G: U to C = 3:4). In loop or bulge positions without secondary structure base pairing, U to C transitions were still frequent, but A to G transitions were rare (A to G: U to C = 1: 5).

Cytokeratin and Desmoplakin Analogues within an Intracellular Parasite.

A significant amount of the total protein in the spore sacs of the microsporidian Thelohania sp. consisted of the cytoskeletal elements, cytokeratin intermediate filaments, and the desmosomal analogues. The cytokeratin and desmosomal analogues were organized as cage envelopes surrounding the spores within the spore sac stage. Thelohania sp. parasitizes the skeletal muscle of Callinectes sapidus, a crustacean that does not appear to have cytokeratins or desmosomes. Immunoprobe data indicate Thelohania sp. has a 240 kDa desmoplakin protein and 48, 51, 54 and 56 kDa cytokeratin polypeptides responsive to antibodies developed against bovine cytoskeletal counterparts. The cytoskeletal envelopes within the Thelohania sp. spore sac stage appear to enhance the stability and viability of the spores.

Ultrastructure of Septa, Asci, and Ascospores of Eremothecium ashbyii

Septa of Eremothecium ashbyii are complete crosswalls (not plugs) and develop by centripetal growth of the hyphal wall. The structure and behavior of spindle pole bodies appear very similar to those of other hemiascomycetous yeasts. Nuclear divisions within spore sacs appear to be uninuclear meiotic divisions. Spore-delimiting membranes develop around individual lobes of dividing nuclei. Wall material forms between the spore-delimiting membranes and consists of an inner light primary layer and an outer dense secondary layer. Spore sacs of E. ashbyii are interpreted as true hemiasci.

Ultrastructure of Septa, Asci, And Ascospores ofEremothecium Ashbyii

Septa of Eremothecium ashbyii are complete crosswalls (not plugs) and develop by centripetal growth of the hyphal wall. The structure and behavior of spindle pole bodies appear very similar to those of other hemiascomycetous yeasts. Nuclear divisions within spore sacs appear to be uninuclear meiotic divisions. Spore-delimiting membranes develop around individual lobes of dividing nuclei. Wall material forms between the spore-delimiting membranes and consists of an inner light primary layer and an outer dense secondary layer. Spore sacs of E. ashbyii are interpreted as true hemiasci.