scholarly journals Major transitions in dinoflagellate evolution unveiled by phylotranscriptomics

2016 ◽  
Vol 114 (2) ◽  
pp. E171-E180 ◽  
Author(s):  
Jan Janouškovec ◽  
Gregory S. Gavelis ◽  
Fabien Burki ◽  
Donna Dinh ◽  
Tsvetan R. Bachvaroff ◽  
...  
Keyword(s):  
Cell Division ◽  
Dna Binding Proteins ◽  
Tetrapyrrole Biosynthesis ◽  
Molecular Fossil ◽  
Free Living ◽  
Major Transitions ◽  
Single Origin ◽  
Key Species ◽  
Phylogenetic Framework ◽  
Group Relationships

Dinoflagellates are key species in marine environments, but they remain poorly understood in part because of their large, complex genomes, unique molecular biology, and unresolved in-group relationships. We created a taxonomically representative dataset of dinoflagellate transcriptomes and used this to infer a strongly supported phylogeny to map major morphological and molecular transitions in dinoflagellate evolution. Our results show an early-branching position of Noctiluca, monophyly of thecate (plate-bearing) dinoflagellates, and paraphyly of athecate ones. This represents unambiguous phylogenetic evidence for a single origin of the group’s cellulosic theca, which we show coincided with a radiation of cellulases implicated in cell division. By integrating dinoflagellate molecular, fossil, and biogeochemical evidence, we propose a revised model for the evolution of thecal tabulations and suggest that the late acquisition of dinosterol in the group is inconsistent with dinoflagellates being the source of this biomarker in pre-Mesozoic strata. Three distantly related, fundamentally nonphotosynthetic dinoflagellates, Noctiluca, Oxyrrhis, and Dinophysis, contain cryptic plastidial metabolisms and lack alternative cytosolic pathways, suggesting that all free-living dinoflagellates are metabolically dependent on plastids. This finding led us to propose general mechanisms of dependency on plastid organelles in eukaryotes that have lost photosynthesis; it also suggests that the evolutionary origin of bioluminescence in nonphotosynthetic dinoflagellates may be linked to plastidic tetrapyrrole biosynthesis. Finally, we use our phylogenetic framework to show that dinoflagellate nuclei have recruited DNA-binding proteins in three distinct evolutionary waves, which included two independent acquisitions of bacterial histone-like proteins.

Stimulation of cell division and DNA replication inPrototheca richardsiby passage through larval amphibian guts

Parasitology ◽  
1993 ◽  
Vol 107 (2) ◽  
pp. 119-124 ◽  
Author(s):  
T. J. C. Beebee ◽  
A. L.-C. Wong
Keyword(s):  
Cell Division ◽  
Dna Replication ◽  
Growth Inhibition ◽  
Dna Synthesis ◽  
Free Living ◽  
Leucine Uptake ◽  
Amphibian Larvae ◽  
Larval Amphibian ◽  
Stimulation Of

SUMMARYPrototheca richardsi, an unpigmented heterotrophic alga, causes growth inhibition in amphibian larvae and has proved refractory to culturein Vitro.P. richardsireplication is dependent on regular passaging through tadpole digestive systems; uptake of thymidine by free-livingProtothecacells and incorporation into DNA are very low by comparison with leucine uptake and incorporation into protein, but DNA synthesis is detectable in cells isolated from tadpole intestines. DNA replication was elicited 6–8 h after ingestion in protothecans fed to tadpoles and subsequently re-isolated from them, providing that the tadpoles were fed subsequent to the ingestion. It appears that passaging through tadpole intestines provides an essential stimulus to maintaining an active cell division cycle inP. richardsi.

scholarly journals Insights into the ancestral flowers of Ranunculales

2020 ◽  
Vol 194 (1) ◽  
pp. 23-46 ◽  
Author(s):  
Laetitia Carrive ◽  
Boris Domenech ◽  
Hervé Sauquet ◽  
Florian Jabbour ◽  
Catherine Damerval ◽  
...  
Keyword(s):  
Floral Organ ◽  
Ancestral State ◽  
Sources Of Uncertainty ◽  
Single Origin ◽  
Reconstruction Methods ◽  
Floral Diversity ◽  
Organ Identity ◽  
Repeated Evolution ◽  
Phylogenetic Framework ◽  
Ordinal Level

Abstract The question of the origin of petals has long been debated in the botanical literature. Ranunculales are characterized by a spectacular floral diversity, particularly at the perianth level. Recent progress in understanding the genetic bases of floral organ identity suggests a single origin for petals in Ranunculaceae, contrasting with the traditional morphological hypothesis of repeated evolution. However, perianth evolution at the ordinal level remains incompletely understood. Recent advances in the elucidation of phylogenetic relationships in the order now provide a new opportunity to study character evolution with model-based methods. We used ancestral state reconstruction methods that take into account various sources of uncertainty to reconstruct the evolution of floral traits at the scale of Ranunculales using a consensus phylogenetic framework of 144 terminal species representing all families in the order. Ancestrally, Ranunculales probably had three trimerous whorls of perianth organs differentiated into two categories of petaloid organs differing in their shape. Each whorl was further lost or duplicated. Moreover, our results support the hypothesis of a single origin of highly specialized (elaborate) nectariferous petals in Ranunculaceae.

scholarly journals Morphotype of bacteroids in different legumes correlates with the number and type of symbiotic NCR peptides

2017 ◽  
Vol 114 (19) ◽  
pp. 5041-5046 ◽  
Author(s):  
Jesús Montiel ◽  
J. Allan Downie ◽  
Attila Farkas ◽  
Péter Bihari ◽  
Róbert Herczeg ◽  
...  
Keyword(s):  
Cell Division ◽  
Amino Acid ◽  
Morphological Changes ◽  
Vesicle Formation ◽  
Cationic Peptides ◽  
Cell Enlargement ◽  
Irreversible Loss ◽  
Single Origin ◽  
Wide Range ◽  
Surface Polysaccharides

In legume nodules, rhizobia differentiate into nitrogen-fixing forms called bacteroids, which are enclosed by a plant membrane in an organelle-like structure called the symbiosome. In the Inverted Repeat-Lacking Clade (IRLC) of legumes, this differentiation is terminal due to irreversible loss of cell division ability and is associated with genome amplification and different morphologies of the bacteroids that can be swollen, elongated, spherical, and elongated–branched, depending on the host plant. In Medicago truncatula, this process is orchestrated by nodule-specific cysteine-rich peptides (NCRs) delivered into developing bacteroids. Here, we identified the predicted NCR proteins in 10 legumes representing different subclades of the IRLC with distinct bacteroid morphotypes. Analysis of their expression and predicted sequences establishes correlations between the composition of the NCR family and the morphotypes of bacteroids. Although NCRs have a single origin, their evolution has followed different routes in individual lineages, and enrichment and diversification of cationic peptides has resulted in the ability to impose major morphological changes on the endosymbionts. The wide range of effects provoked by NCRs such as cell enlargement, membrane alterations and permeabilization, and biofilm and vesicle formation is dependent on the amino acid composition and charge of the peptides. These effects are strongly influenced by the rhizobial surface polysaccharides that affect NCR-induced differentiation and survival of rhizobia in nodule cells.

Ultrastructural features of the tomont of Cryptocaryon irritans (Ciliophora: Prostomatea), a parasitic ciliate of marine fishes

Parasitology ◽  
2017 ◽  
Vol 144 (6) ◽  
pp. 720-729 ◽  
Author(s):  
RUI MA ◽  
XINPENG FAN ◽  
FEI YIN ◽  
BING NI ◽  
FUKANG GU
Keyword(s):  
Cell Division ◽  
Cyst Wall ◽  
Light And Electron Microscopy ◽  
Secretory Vesicles ◽  
Free Living ◽  
Cryptocaryon Irritans ◽  
Daughter Cells ◽  
Molecular Events ◽  
Cellular Metabolic Activity ◽  
Cellular Organelles

SUMMARYNumerous studies have been conducted on the cellular morphology of Cryptocaryon irritans. However, details regarding the tomont stage of its life cycle remain lacking. In this study, we investigated the morphology of the tomont stage throughout encystment and cell division using light and electron microscopy. Results showed that there was no secretion of encystation-specific secretory vesicles or extrusomes during formation of the cyst wall. Instead, the synthesis and construction of the C. irritans cyst wall materials may involve molecular events at the pellicle. The somatic cilia and the cytostome were present during encystment and covered by the newly formed cyst wall. New somatic cilia were continuously created between old cilia and showed various lengths during cell division, a process that was similar to morphogenesis in many free-living ciliates. During cell division inside the tomont, dividing daughter cells formed temporary cell chains with no oral primordia before separating from each other into dissociative tomite precursors. The process of cell division may not be accompanied by stomatogenesis, and new oral primordia in offspring cells likely formed before the dividing cell chains split into dissociative spherical tomites. Mitochondrial autophagy was observed in encysting C. irritans cells. Numerous endosymbionts and Golgi structures were observed in the tomont cytoplasm. Cellular metabolic activity in the C. irritans tomont was quite high, with large amounts of materials or cellular organelles potentially being synthesized and prepared for the following infective theront stage.

scholarly journals Picozoa are archaeplastids without plastid

2021 ◽  
Author(s):  
Max E. Schön ◽  
Vasily V. Zlatogursky ◽  
Rohan P. Singh ◽  
Camille Poirier ◽  
Susanne Wilken ◽  
...  
Keyword(s):  
Single Cell ◽  
Red Algae ◽  
Sister Group ◽  
Free Living ◽  
Plastid Evolution ◽  
Single Origin ◽  
Globally Distributed ◽  
Eukaryotic Supergroup ◽  
Rare Group ◽  
Endosymbiotic Origin

AbstractThe endosymbiotic origin of plastids from cyanobacteria gave eukaryotes photosynthetic capabilities and launched the diversification of countless forms of algae. These primary plastids are found in members of the eukaryotic supergroup Archaeplastida, and are widely assumed to have a single origin. Here, we used single-cell genomics from natural samples combined with phylogenomics to infer the evolutionary origin of the phylum Picozoa, a globally distributed but seemingly rare group of marine microbial heterotrophic eukaryotes. Strikingly, we find based on the analysis of 43 single-cell genomes that Picozoa belong to Archaeplastida as a robust sister group to the clade containing red algae and the phagotrophic rhodelphids. Our analyses of this extensive data support the hypothesis that Picozoa lack a plastid, and further show no evidence for an early cryptic endosymbiosis with cyanobacteria. The position of Picozoa in the eukaryotic tree represents the first known case of a plastid-lacking lineage closely related to one of the main archaeplastid branches. The implications of these findings for our understanding of plastid evolution are unprecedented, and can either be interpreted as the first report of complete plastid loss in a free-living taxon, or as an indication that red algae and rhodelphids obtained their plastids independently of other archaeplastids.

scholarly journals Longitudinal cell division is associated with single mutations in the FtsZ-recruiting SsgB in Streptomyces

2019 ◽  
Author(s):  
Xiansha Xiao ◽  
Joost Willemse ◽  
Patrick Voskamp ◽  
Xinmeng Li ◽  
Meindert Lamers ◽  
...  
Keyword(s):  
Cell Division ◽  
Biochemical Analysis ◽  
Amino Acid Substitutions ◽  
Free Living ◽  
Division Plane ◽  
Z Ring ◽  
Living Bacterium ◽  
Longitudinal Division ◽  
Longitudinal Cell ◽  
Free Living Bacterium

ABSTRACTIn most bacteria, cell division begins with the polymerization of the GTPase FtsZ at the mid-cell, which recruits the division machinery to initiate cell constriction. In the filamentous bacterium Streptomyces, cell division is positively controlled by SsgB, which recruits FtsZ to the future septum sites and promotes Z-ring formation. Here we show via site-saturated mutagenesis that various amino acid substitutions in the highly conserved SsgB protein result in the production of ectopically placed septa, that sever spores diagonally or along the long axis, perpendicular to the division plane. Ectopic septa were especially prominent when cells expressed SsgB variants with substitutions in residue E120. Biochemical analysis of SsgB variant E120G revealed that its interaction with - and polymerization of - FtsZ had been maintained. The crystal structure of S. coelicolor SsgB was resolved and the position of residue E120 suggests its requirement for maintaining the proper angle of helix α3, thus providing a likely explanation for the aberrant septa formed in SsgB E120 substitution mutants. Taken together, our work presents the first example of longitudinal division in a free living bacterium, which is explained entirely by changes in the FtsZ-recruiting protein SsgB.

scholarly journals CRISPR Interference for Rapid Knockdown of Essential Cell Cycle Genes inLactobacillus plantarum

mSphere ◽  
2019 ◽  
Vol 4 (2) ◽  
Author(s):  
Ine Storaker Myrbråten ◽  
Kamilla Wiull ◽  
Zhian Salehian ◽  
Leiv Sigve Håvarstein ◽  
Daniel Straume ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Rna Binding ◽  
Rna Binding Proteins ◽  
Essential Genes ◽  
Content Type ◽  
Genetic Tools ◽  
Guide Rna ◽  
Cell Cycle Genes ◽  
Key Species

ABSTRACTStudies of essential genes in bacteria are often hampered by the lack of accessible genetic tools. This is also the case forLactobacillus plantarum, a key species in food and health applications. Here, we develop a clustered regularly interspaced short palindromic repeat interference (CRISPRi) system for knockdown of gene expression inL. plantarum. The two-plasmid CRISPRi system, in which a nuclease-inactivated Cas9 (dCas9) and a gene-specific single guide RNA (sgRNA) are expressed on separate plasmids, allows efficient knockdown of expression of any gene of interest. We utilized the CRISPRi system to gain initial insights into the functions of key cell cycle genes inL. plantarum. As a proof of concept, we investigated the phenotypes resulting from knockdowns of the cell wall hydrolase-encodingacm2gene and of the DNA replication initiator genednaAand ofezrA, which encodes an early cell division protein. Furthermore, we studied the phenotypes of three cell division genes which have recently been functionally characterized in ovococcal bacteria but whose functions have not yet been investigated in rod-shaped bacteria. We show that the transmembrane CozE proteins do not seem to play any major role in cell division inL. plantarum. On the other hand, RNA-binding proteins KhpA and EloR are critical for proper cell elongation in this bacterium.IMPORTANCEL. plantarumis an important bacterium for applications in food and health. Deep insights into the biology and physiology of this species are therefore necessary for further strain optimization and exploitation; however, the functions of essential genes in the bacterium are mainly unknown due to the lack of accessible genetic tools. The CRISPRi system developed here is ideal to quickly screen for phenotypes of both essential and nonessential genes. Our initial insights into the function of some key cell cycle genes represent the first step toward understanding the cell cycle in this bacterium.

scholarly journals Multiplication and division: Archaic modes of DNA replication initiation

2004 ◽  
Vol 26 (3) ◽  
pp. 11-15
Author(s):  
Nicholas P. Robinson ◽  
Stephen D. Bell
Keyword(s):  
Cell Division ◽  
Dna Replication ◽  
Genetic Material ◽  
Replication Initiation ◽  
Eukaryotic Cells ◽  
Bacterial Cells ◽  
Proliferating Cells ◽  
Dna Replication Initiation ◽  
The Third ◽  
Single Origin

Proliferating cells must produce a complete and accurate copy of their genetic material by DNA replication prior to cell division, and in all organisms this duplication begins at discrete sites known as replication origins. In eukaryotic cells, DNA synthesis is initiated from a large number of these regions, whereas bacterial cells replicate less complex genomes from a single origin. It is only in recent years that the process of replication initiation has become elucidated in the third domain of life, the Archaea.

scholarly journals The Eukaryotic Last Common Ancestor Was Bifunctional for Hopanoid and Sterol Production

2021 ◽  
Author(s):  
Warren Francis
Keyword(s):  
Evolutionary History ◽  
Common Ancestor ◽  
Last Common Ancestor ◽  
Metabolic Demand ◽  
Anaerobic Conditions ◽  
Vertical Inheritance ◽  
Single Origin ◽  
Key Species ◽  
Facultative Aerobe ◽  
History Of

Steroid and hopanoid biomarkers can be found in ancient rocks and may give a glimpse of what life was present at that time. Sterols and hopanoids are produced by two related enzymes, though the evolutionary history of this protein family is complicated by losses and horizontal gene transfers, and appears to be widely misinterpretted. Here, I have added sequences from additional key species, and re-analysis of the phylogeny of SHC and OSC indicates a single origin of both enzymes among eukaryotes. This pattern is best explained by vertical inheritance of both enzymes from a bacterial ancestor, followed by widespread loss of SHC, and two subsequent HGT events to ferns and ascomycetes. Thus, the last common ancestor of eukaryotes would have been bifunctional for both sterol and hopanoid production. Later enzymatic innovations allowed diversification of sterols in eukaryotes. Contrary to previous interpretations, the LCA of eukaryotes potentially would have been able to produce hopanoids as a substitute for sterols in anaerobic conditions. Without invoking any other metabolic demand, the LCA of eukaryotes could have been a facultative aerobe, living in unstable conditions with respect to oxygen level.

Phylogenetic relationships and evolution in the genus Dissodactylus Smith, 1870 (Crustacea: Brachyura: Pinnotheridae)

1987 ◽  
Vol 65 (9) ◽  
pp. 2292-2310 ◽  
Author(s):  
Hugh Griffith
Keyword(s):  
Phylogenetic Relationships ◽  
Sister Group ◽  
Morphological Characters ◽  
The Other ◽  
Free Living ◽  
Evolutionary Scenario ◽  
Species Pairs ◽  
Group Relationships ◽  
Sand Dollars ◽  
Pacific Species

A cladogram indicating sister-group relationships within the pinnotherid crab genus Dissodactylus is constructed from analysis of 28 morphological characters. The outgroup method was used to determine character polarities. Parapinnixa and Sakaina are shown to be a monophyletic group, and are suggested to be the sister group of Dissodactylus. Within Dissodactylus, two mutually exclusive, monophyletic subgroups are found, one containing nine, the other four species. Both of these groups include Atlantic and Pacific representatives. Two Atlantic–Pacific species pairs are suggested to be sister species (D. mellitae–D. glasselli and D. primitivus–D. schmitti). Members of the group of nine species are inhabitants primarily of mellitid sand dollars, although one species, D. primitivus, is a symbiont of heart urchins (Spatangoida). Members of the group of four species are inhabitants of sea biscuits of the genus Clypeaster (Clypeasteridae). An evolutionary scenario is presented, which suggests that a free-living ancestor colonized mellitid sand dollars, and subsequent specializations led to the colonizations of the genus Clypeaster and genera of Spatangoida.

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