Periplast Component Research Articles

Baffinella frigidus gen. et sp. nov. (Baffinellaceae fam. nov., Cryptophyceae) from Baffin Bay: Morphology, pigment profile, phylogeny, and growth rate response to three abiotic factors.

Twenty years ago an Arctic cryptophyte was isolated from Baffin Bay and given strain number CCMP2045. Here, it was described using morphology, water- and non-water soluble pigments and nuclear-encoded SSU rDNA. The influence of temperature, salinity, and light intensity on growth rates was also examined. Microscopy revealed typical cryptophyte features but the chloroplast color was either green or red depending on the light intensity provided. Phycoerythrin (Cr-PE 566) was only produced when cells were grown under low-light conditions (5μmol photons·m-2 ·s-1 ). Non-water-soluble pigments included chlorophyll a, c2 and five major carotenoids. Cells measured 8.2×5.1μm and a tail-like appendage gave them a comma-shape. The nucleus was located posteriorly and a horseshoe-shaped chloroplast contained a single pyrenoid. Ejectosomes of two sizes and a nucleomorph anterior to the pyrenoid were discerned in TEM. SEM revealed a slightly elevated vestibular plate in the vestibulum. The inner periplast component consisted of slightly overlapping hexagonal plates arranged in 16-20 oblique rows. Antapical plates were smaller and their shape less profound. Temperature and salinity studies revealed CCMP2045 as stenothermal and euryhaline and growth was saturated between 5 and 20μmol photons·m-2 ·s-1 . The phylogeny based on SSU rDNA showed that CCMP2045 formed a distinct clade with CCMP2293 and Falcomonas sp. isolated from Spain. Combining pheno- and genotypic data, the Arctic cryptophyte could not be placed in an existing family and genus and therefore Baffinellaceae fam. nov. and Baffinella frigidus gen. et sp. nov. were proposed.

Morphological and molecular characterization of Teleaulax gracilis sp. nov. and T. minuta sp. nov. (Cryptophyceae)

Laza-Martinez A., Arluzea J., Miguel I. and Orive E. 2012. Morphological and molecular characterization of Teleaulax gracilis sp. nov. and T. minuta sp. nov. (Cryptophyceae). Phycologia 51: 649–661. DOI: 10.2216/11-044.1Teleaulax is a genus of delicate cryptophytes that are common and sometimes abundant in marine samples. Previous to this study, only three species (Teleaulax acuta, T. amphioxeia and T. merimbula) were known in the genus. Here, two new species were described from strains isolated from plankton samples collected at the seaward end of the Nervioi-Ibaizabal River estuary (south-eastern Bay of Biscay). They were examined by light microscopy and scanning and transmission electron microscopy, and the nuclear 18S rDNA was sequenced to infer the molecular phylogeny. The species of this genus have been distinguished by size, shape (especially of the cell anterior and posterior), swimming behaviour, morphology of the posterior band and the relative extension of the furrow. The most characteristic traits of Teleaulax gracilis sp. nov. were the cell anterior, that was only slightly rostrate, and the shape of the cell posterior, which tapered off gradually in form of a wedge and finished in a pointed antapex sustained by a V-shaped band. Teleaulax minuta sp. nov., with a length of 5–6.8 μm, is the smallest within the genus and lacks a posterior band. Common features shared with other congeners are, among others, the long furrows, the more or less rostrate cell anteriors and tapered posteriors, a sheet-like internal periplast component thinner than the plasma membrane and the thylakoids arranged in stacks of three.

Nuclear and nucleomorph SSU rDNA phylogeny in the Cryptophyta and the evolution of cryptophyte diversity.

The plastid-bearing members of the Cryptophyta contain two functional eukaryotic genomes of different phylogenetic origin, residing in the nucleus and in the nucleomorph, respectively. These widespread and diverse protists thus offer a unique opportunity to study the coevolution of two different eukaryotic genomes within one group of organisms. In this study, the SSU rRNA genes of both genomes were PCR-amplified with specific primers and phylogenetic analyses were performed on different data sets using different evolutionary models. The results show that the composition of the principal clades obtained from the phylogenetic analyses of both genes was largely congruent, but striking differences in evolutionary rates were observed. These affected the topologies of the nuclear and nucleomorph phylogenies differently, resulting in long-branch attraction artifacts when simple evolutionary models were applied. Deletion of long-branch taxa stabilized the internal branching order in both phylogenies and resulted in a completely resolved topology in the nucleomorph phylogeny. A comparison of the tree topologies derived from SSU rDNA sequences with characters previously used in cryptophyte systematics revealed that the biliprotein type was congruent, but the type of inner periplast component incongruent, with the molecular trees. The latter is indicative of a hidden cellular dimorphism (cells with two periplast types present in a single clonal strain) of presumably widespread occurrence throughout cryptophyte diversity, which, in consequence, has far-reaching implications for cryptophyte systematics as it is practiced today.

A revised classification of Cryptophyta

Abstract The systematics of currently recognized cryptomonad genera is reviewed. Complete ultraIstructural descriptions are provided for each genus, and are based on the most recent observations in the literature. Using ultrastructural, biochemical and molecular data, a classification scheme, which delineates 16 genera, is proposed for the Cryptophyta. This scheme accommodates two classes, the Cryptophyceae and the Goniomonadea. These differ primarily in that the former possesses a plastidial complex whereas the latter lacks one. Three orders are discussed and are separated on the basis of colour. The order GonioImonadales, which consists of a single genus, is aplastidal and colourless. The order Cryptomonadales has two families and contains the accessory pigment Cr-phycoerythrin 566 which imparts a brown colour to the cells. The constituent families, Cryptomonadaceae and Campylomonadaceae, are separated by variations in the furrow/gullet complex, the inner periplast component (IPC), nucleomorph position, and the type of rhizostyle. The order Pyrenomonadales contains four families. It is the sister group to the Cryptomonadales and possesses the accessory pigments Cr-phycoerythrin 545, 555, and these impart a red colour to the cells, or other members that possess Cr-phycocyanin 630, 645, or 569, which impart a blue-green colour to the cells. The four families are separated on the basis of phycobiliprotein type and, where appropriate, a combination of nucleomorph placement, type of IPC, rhizostyle type, and furrow plate type. This scheme accommodates three new families, the Campylomonadaceae, Geminigeraceae, and Chroomonadaceae.

A revised classification of Cryptophyta

The systematics of currently recognized cryptomonad genera is reviewed. Complete ultraÍstructural descriptions are provided for each genus, and are based on the most recent observations in the literature. Using ultrastructural, biochemical and molecular data, a classification scheme, which delineates 16 genera, is proposed for the Cryptophyta. This scheme accommodates two classes, the Cryptophyceae and the Goniomonadea. These differ primarily in that the former possesses a plastidial complex whereas the latter lacks one. Three orders are discussed and are separated on the basis of colour. The order GonioÍmonadales, which consists of a single genus, is aplastidal and colourless. The order Cryptomonadales has two families and contains the accessory pigment Cr-phycoerythrin 566 which imparts a brown colour to the cells. The constituent families, Cryptomonadaceae and Campylomonadaceae, are separated by variations in the furrow/gullet complex, the inner periplast component (IPC), nucleomorph position, and the type of rhizostyle. The order Pyrenomonadales contains four families. It is the sister group to the Cryptomonadales and possesses the accessory pigments Cr-phycoerythrin 545, 555, and these impart a red colour to the cells, or other members that possess Cr-phycocyanin 630, 645, or 569, which impart a blue-green colour to the cells. The four families are separated on the basis of phycobiliprotein type and, where appropriate, a combination of nucleomorph placement, type of IPC, rhizostyle type, and furrow plate type. This scheme accommodates three new families, the Campylomonadaceae, Geminigeraceae, and Chroomonadaceae.

ULTRASTRUCTURE AND SYSTEMATICS OF TWO NEW FRESHWATER RED CRYPTOMONADS, STOREATULA RHINOSA, SP. NOV. AND PYRENOMONAS OVALIS, SP. NOV.

The ultrastructure and systematics of two red colored freshwater cryptomonads, Storeatula rhinosa, sp. nov. and Pyrenomonas ovalis, sp. nov., are described for the first time. Storeatula, which had been described from marine waters only, has a single inner periplast sheet and a fibrous surface periplast component. Cells lack a furrow but possess a gullet, a bilobed chloroplast connected by a pyrenoid and a nucleomorph located in an indentation of the pyrenoid. This freshwater Storeatula possesses the same general features as the marine species, but it has a contractile vacuole and lacks the lobed chloroplast of S. major. P. ovalis has the generic characteristics described for marine species of Rhodomonas. These characteristics include a short furrow, a deep gullet, square inner periplast plates with beveled corners, a slightly fibrillar surface periplast component, a single chloroplast with two lobes connected by a pyrenoidal bridge and a nucleomorph located in an indentation of the pyrenoid.

The surface periplast component of the protistKomma caudata (Cryptophyceae) self-assembles from a secreted high-molecular-mass polypeptide

The cell covering of the cryptomonadKomma caudata (Geitler) Hill is a trilaminar structure consisting of a surface periplast component (SPC) and an inner periplast component (IPC) that sandwich the plasma membrane. In order to investigate the development of the periplast, we have raised monoclonal antibodies against the cell surface ofK. caudata. Immunoblot analyses using one of these antibodies, K1/D.10, showed that it labeled a high-molecular-mass polypeptide. Immunofluorescence and pre- and post-embedding immunogold labeling studies demonstrated that the antibody recognized sites on the cell surface corresponding to the SPC plates and anotherK. caudata cell surface component, the rosulate scales. Labeling was also detected on surface domains devoid of periplast, namely the vestibular/gullet region of the cell. Post-embedding immunocytochemistry revealed that intracellular sites labeled with K1/D.10 included the Golgi apparatus and its associated vesicles. We propose that the subunits of theK. caudata cell covering are antigenically related molecules and that they self-assemble on the cell surface after secretion via the endomembrane system and deployment at the vestibular/gullet region or, in dividing cells, the cytokinetic furrow.

Periplast development in Cryptophyceae II. Development of the inner periplast component inRhinomonas pauca, Proteomonas sulcata [haplomorph],Rhodomonas baltica, andCryptomonas ovata

The inner periplast component (IPC) of numerous cryptomonads is composed of discrete inner plates, situated beneath (and intimately associated with) the plasma membrane (PM). Freeze-fracture images reveal that the PM is organized into a series of ordered structural domains, which directly correspond in size and shape to the underlying inner plates. Freeze-fracture images are used here to compare IPC arrangement inRhinomonas pauca, Proteomonas sulcata [haplomorph],Rhodomonas baltica, andCryptomonas ovata, and to examine development of inner plates in these cryptomonads. In all genera examined, the IPC is highly ordered across most of the cell periphery but appears to be modified adjacent to the vestibulum and mid-ventral line, which represent the anamorphic zones. Variations in the size and shape of PM domains in these regions suggest that development of the IPC occurs within anamorphic zones, by the de novo formation and enlargement of inner plates throughout the cell cycle.

Periplast development in Cryptophyceae III. Development of crystalline surface plates inFalcomonas daucoides, Proteomonas sulcata [haplomorph], andKomma caudata

In several cryptomonad genera the surface periplast component (SPC) is composed of discrete crystalline plates surrounded by structurally distinct borders. Freeze-etch images enable detailed investigation of surface microarchitecture in these cryptomonads, and reveal that the plates consist of precisely aligned arrays of minute subunits. The plate borders are composed of similar subunits which display marked variations in alignment. Differences in the arrangement of subunits within the plates and borders appear closely linked to the organization of the underlying plasma membrane (PM) and inner periplast component (IPC). Development of the crystalline surface plates occurs within specialized anamorphic zones located along the mid-ventral line and around the vestibular margins of cells. Examination of variations in surface microarchitecture within anamorphic zones suggests that the crystalline plates form directly on the cell surface. Development of the surface plates results from the accumulation and self-assembly of subunits, while orderly addition of subunits to plate edges facilitates subsequent growth and enlargement. The close structural relationship between the SPC, PM, and IPC in these cryptomonads suggests that self-assembly of the surface plates may be mediated by developmental changes in the underlying PM and IPC.

The structure of the periplast components and their association with the plasma membrane in a cryptomonad flagellate

The periplast of Cryptomonas sp. θ covers most of the cell surface and is composed of the plasma membrane sandwiched between inner and surface periplast components. The surface periplast component is tightly appressed to the plasma membrane and consists of irregularly shaped plates composed of subunits organized into a crystalline array. Noncrystalline material distinguishes plate borders, and changes in plate size and (or) shape may result from the addition or subtraction of subunits at the borders. The inner periplast component is difficult to discern, but normally appears as a thin sheet of material appressed to the cytoplasmic surface of the plasma membrane. The inner periplast component is not closely associated with the plasma membrane at the positions corresponding to plate borders in the overlying surface periplast component. Both periplast components end at the entrance to the vestibulum, which together with the gullet is covered by a surface layer of heptagonal "rosette scales." The size and shape of the surface periplast plates, as well as the degree of association of the inner periplast sheet with the plasma membrane, are mirrored in the P and, to a lesser degree, E fracture faces of the plasma membrane. The presence of distinct membrane domains suggests the plasma membrane may be directly involved in the assembly and subsequent development of the periplast layers.

Periplast structure of the cryptomonad flagellateHemiselmis brunnescens

The periplast ofHemiselmis brunnescensButcher is a complex cell covering comprised of the plasma membrane (PM) sandwiched between a surface periplast component (SPC) and an inner periplast component (IPC). The SPC is revealed by deep-etching, and consists of hexagonal plates composed of tripartite subunits that appear to self-assemble into a crystalline layer with a hexagonal symmetry. Small scales (termed fibrillar scales) accumulate on the crystalline plates during cell growth, eventually forming a “carpet” that itself may appear crystalline when fully formed. Heptagonal “rosette scales” are occasionally observed on the surface as well. The position of the crystalline plates is precisely mirrored by both the E and P fracture faces of the PM. The plate proper is underlain by membrane with a high concentration of intramembrane particles (IMPs) while the bands of membrane underlying the plate borders lack IMPs. Access of subunits and fibrillar scales to the cell surface following initial plate formation appears to be at the plate boundaries. This study suggests that cryptomonad flagellates may provide model systems for studying the self-assembly of cell surface components, and for relating membrane structure to function, as evidence suggests a major role for the PM in mediating periplast assembly and development.

A comparative study of periplast structure inCryptomonas cryophila andC. ovata (Cryptophyceae)

Freeze-fracture followed by deep-etch was used with transmission electron microscopy to characterize and compare the periplasts of two cryptomonads,Cryptomonas ovata andC. cryophila. The periplast ofC. ovata consists of a dense surface mat of granular/fibrillar material overlying a series of polygonal plates attached to the undersurface of the plasma membrane (PM) at their upturned edges. Fracture faces of the PM reveal a highly stable substructure with distinct patterns of intra-membrane particles (IMPs) associated with the underlying plates; a role for the PM in plate development is indicated. The surface periplast component ofC. cryophila exhibits a cover of morphologically complex, overlapping heptagonal scales (termed rosette scales) in addition to elongate fibrils. The arrangement of IMPs within the PM is predominantly random and the inner periplast component consists of a sheet with regular pores where ejectisomes are located. The sheet does not appear closely associated with the PM. The combination of features exhibited by the periplast ofC. cryophila warrants its inclusion as a new type within theCryptophyceae.