Spectral properties of a pigmented body in Hymenomonas sp.: an extra-chloroplast organelle containing chlorophyll

In the chrysomonad Hymenomonas, a lamellar organelle of undefined function described previously in electron micrographs, is shown to be highly pigmented by absorption and fluorescence light microscopy. Absorption spectra of the lamellar organelle and the chloroplasts of Hymenomonas are presented. In comparison with the chloroplast the lamellar body appears to have an equal concentration of chlorophyll α and nearly three times the concentration of the 490 nm absorbing carotenoid. Fluorescence in the organelle is initially red as in the chloroplast; this is quickly replaced by an intense yellow emission. The rate at which the red fluorescence is replaced by the yellow is oxidation dependent and is quite rapid in the high intensity of the exciting light required for fluorescence micrographs. Possible roles of the organelle in cell metabolism or photochemistry which are considered and evaluated include: photosynthetic organelle, coccolithogenic organelle, symbiont and lysosome.     

ATPase and cytochrome oxidase activities at the polar organelle in swarm cells of Sphaerotilus natans: an ultrastructural study

The polar organelle of bacteria presumably is part of the flagellar apparatus. In order to characterize this structure, cytochemical studies on Sphaerotilus natans have been performed.Marked ATPase activity is associated with the inner boundary layer and central layer of this organelle. The spaces between the boundary layers and the central layer of the polar organelle which are traversed by fine fibrilles are positive for reactions with diaminobenzidine. This indicates cytochrome oxidase activity. S. natans possesses a ribbon-like, helically shaped polar organelle which is divided concomitantly with cell fission, possibly explaining inheritance of this structure and of the flagellar apparatus.Dedicated to Prof. G. Drews on occasion of his 60th birthday     

The Cytostome of Trypanosoma cruzi and T. conorhini*

SYNOPSIS. A cytostome is described in culture forms and in intracellular stages of Trypanosoma cruzi and in culture forms of T. conorhini. The organelle opens into the flagellar pocket or close to it and runs deeply into the cell.     

Isolation of protein bodies on sucrose gradients

Summary Storage protein bodies from sunflower cotyledons during early stages of seed germination were isolated on sucrose density gradients by isopycnic centrifugation. The density of this organelle on the gradients ranged between 1.26 and 1.36 g cm^-3. A proteinase with a pH optimum of 5.2 was associated with this organelle, and is probably responsible for degradation of storage protein. A NADH-dependent cytochrome-c reductase, a membrane marker enzyme with a pH optimum of 8.4, was also present in this organelle fraction.Abbreviations LPA for l-lysine-p-nitroanilide - LPAase for the peptidase which hydrolyzes this peptide This work was supported in part by the National Science Foundation Grant GB-17543, and published as Journal Article No. 5736 of the Michigan Agricultural Experiment Station.Supported by a Deutsche Forschungsgemeinschaft Fellowship.     

Fine Structure of the Mastigont System in Tritrichomonas muris (Grassi)*

SYNOPSIS. Tritrichomonas muris shares many fine-structural details with the previously described members of the family Trichomonadidae, and especially with the organisms belonging to the subfamily Tritrichomonadinae. Among the features which T. muris has in common with all Trichomonadidae and in all probability with other Trichomonadida are the arrangement and structure of: the kinetosomes; many rootlet filaments, including the sigmoid filaments of kinetosome #2; the parabasal apparatus; and the pelta-axostyle complex. The structures which T. muris-type flagellates share with other Tritrichomonadinae, and especially with Tritrichomonas augusta-type species (including T. foetus), but not with Trichomonadinae that have been studied to date, are: the Type A costa; a comb-like structure, which appears to have replaced the costal base of Trichomonadinae and of Hypotrichomonas; the suprakinetosomal body, rudimentary in T. muris; and the infrakinetosomal body. The undulating membrane, like that of T. augusta-type organisms, consists of a proximal and a distal part. The proximal part, which contains the proximal marginal lamella, is less developed in T. muris than in T. augusta-type flagellates, being represented by a relatively low ridge for the entire length of the organism. The distal part of the membrane in T. muris, on the other hand, is more highly developed; it is a heavy cord, with a distal marginal lamella which consists of a large triangular organelle having a highly ordered structure and 2 less well defined cords distal to this organelle. The tubules of the recurrent flagellum occupy the area distal to the cords. The sigmoid filaments of kinetosome #2, unlike those of other Trichomonadidae examined to date, extend posteriorly to the peltar-axostylar junction; they seem to terminate within the cytoplasm near, but not connected to the axostyle. In addition to the Type A costa, there is a small rootlet filament, which appears to be homologous to the rudimentary costa noted in Hypotrichomonas. Some of the paraxostylar and paracostal granules consist of an outer, relatively dense layer and an inner “core” of moderate density; between the 2 there is a lucent ring. The discussion deals in some detail with the possible nature of the paraxostylar and paracostal granules in trichomonads. The taxonomic status of Tritrichomonas cricetus (Wantland) [Tritrichomonas criceti (Wantland) emend. Levine] and Trichomonas criceti Ray & Sen Gupta is discussed in an appendix; it is concluded that both of these names are synonyms of T. muris (Grassi).     

Electron cryotomography of Mycoplasma pneumoniae mutants correlates terminal organelle architectural features and function

The Mycoplasma pneumoniae terminal organelle functions in adherence and gliding motility and is comprised of at least eleven substructures. We used electron cryotomography to correlate impaired gliding and adherence function with changes in architecture in diverse terminal organelle mutants. All eleven substructures were accounted for in the prkC, prpC and P200 mutants, and variably so for the HMW3 mutant. Conversely, no terminal organelle substructures were evident in HMW1 and HMW2 mutants. The P41 mutant exhibits a terminal organelle detachment phenotype and lacked the bowl element normally present at the terminal organelle base. Complementation restored this substructure, establishing P41 as either a component of the bowl element or required for its assembly or stability, and that this bowl element is essential to anchor the terminal organelle but not for leverage in gliding. Mutants II‐3, III‐4 and topJ exhibited a visibly lower density of protein knobs on the terminal organelle surface. Mutants II‐3 and III‐4 lack accessory proteins required for a functional adhesin complex, while the topJ mutant lacks a DnaJ‐like co‐chaperone essential for its assembly. Taken together, these observations expand our understanding of the roles of certain terminal organelle proteins in the architecture and function of this complex structure.     

Axostyle structure in the termite protozoon Pyrsonympha vertens

The axostyle of Pyrsonympha vertens is a cellular organelle composed of interconnected microtubules. In living organisms the axostyle has waves which originate at the anterior end of the protozoon and traverse the length to the posterior end of the protozoon so that an average of 3–4 waves are present in the organelle at any given point in time. The part of the axostyle between the waves is straight. In sections through the middle of the straight part, the microtubules are hexagonally packed, with predominant connections between tubules in rows across the width of the axostyle, but the microtubules are rectilinearly packed through the wave. The wave appears to involve changes in orientation and arrangement of the microtubules. The general structure of the microtubules, cross-bridges and axostyle in the straight and bent portions are described and related to the wave propagation by this organelle.     

The intracellular location of the enzymes of nitrate assimilation in the apices of seedling pea roots

The intracellular distribution of the enzymes of nitrate and ammonia assimilation in apical cells of pea (Pisum sativum L.) roots is described. Nitrate reductase (EC 1.6.6.2) was found to have no organelle association, and is considered to be located in the cytosol or possibly loosely bound to the outside of an organelle. Nitrite reductase and glutamate synthase (EC 2.6.1.53) are plastid located, as is glutamine synthetase (EC 6.3.1.2) although this enzyme also has activity in the cytosol. Glutamate dehydrogenase (EC 1.4.1.3) was found only in the mitochondrion.     

Analysis of mitochondrial and chloroplast genomes in two volvocine algae: Eudorina elegans and Eudorina cylindrica (Volvocaceae,Chlorophyta)

The colonial volvocine algae span the full range of organizational complexity, from four-celled species to multicellular species, and this group of algae is often used for the study of evolution. In recent years, many organelle genomes have been sequenced using the application of next generation sequencing technology; however, only a few organelle genomes have been reported in colonial volvocine algae. In this study, we determined the organelle genomes of Eudorina elegans and Eudorina cylindrica and analysed the organelle genome size, structure and gene content between these volvocine species. This provided useful information to help us understand the composition of colonial volvocine organelle genomes. Based on the chloroplast genome protein-coding genes, we conducted a phylogenomics analysis of the volvocine algae. The result revealed an unexpected phylogenetic relationship, namely, E. elegans is more closely related to Pleodorina starrii than to E. cylindrica. The substitution rate of volvocine algae was then calculated based on organelle genome protein-coding genes; our analysis suggested the possibility that the two Eudorina species may be under similar evolutionary pressure. Lastly, the synteny analysis of the mitochondrial genome showed that gene arrangements and contents are highly conserved in the family Volvocaceae, and the synteny analysis of the chloroplast genome indicated that the genus Eudorina may have experienced genomic changes.     

Behavior of organelle nuclei (nucleoids) in generative and vegetative cells during maturation of pollen inLilium longiflorum andPelargonium zonale

Summary The behavior of organelle nuclei during maturation of the male gametes ofLilium longiflorum andPelargonium zonale was examined by fluorescence microscopy after staining with 4,6-diamidino-2-phenylindole (DAPI) and Southern hybridization. The organelle nuclei in both generative and vegetative cells inL. longiflorum were preferentially degraded during the maturation of the male gametes. In the mature pollen grains ofL. longiflorum, there were absolutely no organelle nuclei visible in the cytoplasm of the generative cells. In the vegetative cells, almost all the organelle nuclei were degraded. However, in contrast to the situation in generative cells, the last vestiges of organelle nuclei in vegetative cells did not disappear completely. They remained in evidence in the vegetative cells during germination of the pollen tubes. InP. zonale, however, no evidence of degradation of organelle nuclei was ever observed. As a result, a very large number of organelle nuclei remained in the sperm cells during maturation of the pollen grains. When the total DNA isolated from the pollen or pollen tubes was analyzed by Southern hybridization with a probe that contained therbc L gene, for detection of the plastid DNA and a probe that contained thecox I gene, for detection of the mitochondrial DNA, the same results were obtained. Therefore, the maternal inheritance of the organelle genes inL. longiflorum is caused by the degradation of the organelle DNA in the generative cells while the biparental inheritance of the organelle genes inP. zonale is the result of the preservation of the organelle DNA in the generative and sperm cells. To characterize the degradation of the organelle nuclei, nucleolytic activities in mature pollen were analyzed by an in situ assay on an SDS-DNA-gel after electrophoresis. The results revealed that a 40kDa Ca²⁺-dependent nuclease and a 23 kDa Zn²⁺ -dependent nuclease were present specifically among the pollen proteins ofL. longiflorum. By contrast, no nucleolytic activity was detected in a similar analysis of pollen proteins ofP. zonale.     

Observations on the Caudal Cilium of the Tomite of Ichthyophthirius multifiliis Fouquet, 18761,2

Light microscopy of live or silver-impregnated specimens of the fish parasite Ichthyophthirius multifiliis show that the tomites are elongated and claviform with the anterior end broad. The cytostome, indicated by the presence of the organelle of Lieberkühn, is found in the lower part of the broadened anterior third of the tomite. The tapered posterior end bears a rigid, caudal cilium at its pole. Scanning electron microscopy reveals the caudal cilium and associated structures, including the depression from which the cilium protrudes, circumciliary ring, and raised struts on the ring. From these observations it is concluded that a previously reported “apical filament” found on the tomite is actually the posterior caudal cilium described by Canella & Rocchi-Canella in 1976.     

Unparalleled GC content in the plastid DNA of Selaginella

One of the more conspicuous features of plastid DNA (ptDNA) is its low guanine and cytosine (GC) content. As of February 2009, all completely-sequenced plastid genomes have a GC content below 43% except for the ptDNA of the lycophyte Selaginella uncinata, which is 55% GC. The forces driving the S. uncinata ptDNA towards G and C are undetermined, and it is unknown if other Selaginella species have GC-biased plastid genomes. This study presents the complete ptDNA sequence of Selaginella moellendorffii and compares it with the previously reported S. uncinata plastid genome. Partial ptDNA sequences from 103 different Selaginella species are also described as well as a significant proportion of the S. moellendorffii mitochondrial genome. Moreover, S. moellendorffii express sequence tags are data-mined to estimate levels of plastid and mitochondrial RNA editing. Overall, these data are used to show that: (1) there is a genus-wide GC bias in Selaginella ptDNA, which is most pronounced in South American articulate species; (2) within the Lycopsida class (and among plants in general), GC-biased ptDNA is restricted to the Selaginella genus; (3) the cause of this GC bias is arguably a combination of reduced AT-mutation pressure relative to other plastid genomes and a large number of C-to-U RNA editing sites; and (4) the mitochondrial DNA (mtDNA) of S. moellendorffii is also GC biased (even more so than the ptDNA) and is arguably the most GC-rich organelle genome observed to date—the high GC content of the mtDNA also appears to be influenced by RNA editing. Ultimately, these findings provide convincing support for the earlier proposed theory that the GC content of land-plant organelle DNA is positively correlated and directly connected to levels of organelle RNA editing.     

Annulate lamellae in hindgut epithelial cells ofIsopoda

Summary Hindgut epithelial cells of the aquatic isopod,Asellus communis, and the terrestrial isopod,Armadillidium vulgare, possess annulate lamellae. The organelle is present in non-dividing cells of intermolt adult organisms. The lamellae exhibit dense pore areas traversed by diaphragms, and the lamellae are associated with elements of endoplasmic reticulum.This research was supported in part by a grant to E. R. Witkus from the Irene Heinz and John La Porte Given Foundation.     

Characterization of a novel organelle in Toxoplasma gondii with similar composition and function to the plant vacuole

Toxoplasma gondii belongs to the phylum Apicomplexa and is an important cause of congenital disease and infection in immunocompromised patients. Like most apicomplexans, T. gondii possesses several plant‐like features, such as the chloroplast‐like organelle, the apicoplast. We describe and characterize a novel organelle in T. gondii tachyzoites, which is visible by light microscopy and possesses a broad similarity to the plant vacuole. Electron tomography shows the interaction of this vacuole with other organelles. The presence of a plant‐like vacuolar proton pyrophosphatase (TgVP1), a vacuolar proton ATPase, a cathepsin L‐like protease (TgCPL), an aquaporin (TgAQP1), as well as Ca²⁺/H⁺ and Na⁺/H⁺ exchange activities, supports similarity to the plant vacuole. Biochemical characterization of TgVP1 in enriched fractions shows a functional similarity to the respective plant enzyme. The organelle is a Ca²⁺ store and appears to have protective effects against salt stress potentially linked to its sodium transport activity. In intracellular parasites, the organelle fragments, with some markers colocalizing with the late endosomal marker, Rab7, suggesting its involvement with the endocytic pathway. Studies on the characterization of this novel organelle will be relevant to the identification of novel targets for chemotherapy against T. gondii and other apicomplexan parasites as well.     

The juxtatesticular body of jawfishes (Teleostei,Opistognathidae): Comparative morphology and fine structure

A peculiar gland, the juxtatesticular body (JTB), ductless and consisting of follicles, had previously been discovered in males of two Opistognathus species (Teleostei, Opistognathidae). In this paper, we describe (1) the general morphology of the JTB in an additional two Opistognathus species, O. aurifrons and O. macrognathus, comparing it with that of the previously described species, and (2) the fine structure of the JTB of Opistognathus whitehurstii and O. maxillosus. Interspecific variability occurs both in the general organization of this gland and in the number of follicular cells. Fine structural analysis of the JTB, both in O. whitehurstii and O. maxillosus, reveals strong similarities with thyroid follicular cells, suggesting a similar pattern of synthesis and secretion. JTB follicular cells are arranged as a monolayered epithelium that surrounds a follicular lumen; they show a polarity in organelle distribution and membrane specialization typical of secreting cells. On the basis of their cytological and histochemical characteristics we propose that JTB follicular cells perform two major types of secretory activities: the secretion of a glycoprotein from the apical part of the cells into the follicular lumen and the endocrine, or paracrine, secretion of a still unknown substance(s) from the basal part of the cell either into the extrafollicular space or the blood or both. A hypothesis concerning the functional cycle of JTB follicle is also discussed. © 1995 Wiley-Liss, Inc.     

ULTRASTRUCTURE OF PRYMNESIUM NEMAMETHECUM SP. NOV. (PRYMNESIOPHYCEAE)1

Based on material collected from Cape Town, a new sand-dwelling, marine species of Prymnesium is described. Using light and electron microscopy, Prymnesium nemamethecum sp. nov. has been found to resemble other species of the genus in size, organelle arrangement, and swimming behavior. It differs from other described species in that it has three types of scales, one of which is confined to the region of appendage insertion and forms a sheath of simple plate scales over the haptonema. In addition, the scales constituting the proximal body scale layer(s) are unusual because they are not simple plate scales but are specifically ornamented.     

Giant chloroplast development in ethylene response1-1 is caused by a second mutation in ACCUMULATION AND REPLICATION OF CHLOROPLAST3 in Arabidopsis

The higher plants of today array a large number of small chloroplasts in their photosynthetic cells. This array of small chloroplasts results from organelle division via prokaryotic binary fission in a eukaryotic plant cell environment. Functional abnormalities of the tightly coordinated biochemical event of chloroplast division lead to abnormal chloroplast development in plants. Here, we described an abnormal chloroplast phenotype in an ethylene insensitive ethylene response1-1 (etr1-1) of Arabidopsis thaliana. Extensive transgenic and genetic analyses revealed that this organelle abnormality was not linked to etr1-1 or ethylene signaling, but linked to a second mutation in ACCUMULATION AND REPLICATION3 (ARC3), which was further verified by genetic complementation analysis. Despite the normal expression of other plastid division-related genes, the loss of ARC3 caused the enlargement of chloroplasts as well as the diminution of a photosynthetic protein Rubisco in etr1-1. Our study has suggested that the increased size of the abnormal chloroplasts may not be able to fully compensate for the loss of a greater array of small chloroplasts in higher plants.     

Fine structural distribution of the surface-connected canalicular system in frog thrombocytes

Summary The existence of the surface-connected canalicular system (SCCS) has been demonstrated in semithick sections of the frog thrombocytes by the use of a high voltage electron microscope. The SCCS of the thrombocytes in Rana catesbeiana and Rana nigromaculata consists of numerous canaliculi and vesicles with a diameter of 250 nm, which join with one another to make a complex network throughout the cytoplasm. Although the SCCS of Xenopus laevis fits well into the pattern described in Rana catesbeiana, the diameter of the canaliculi of the SCCS is about 500 nm. The results of this study suggest that the SCCS is a specific organelle of the thrombocyte system common to submammals and mammals.