Novel Data About Unusual Location of Toxoplasma Gondii Within Active Microbial Community in the Anterior Chamber of the Eye of Egyptian Rural Children

In Egypt, many cases of granulomatous anterior uveitis consisting of single or multiple gelatinous nodules were detected in children living in rural areas. These lesions are believed to be waterborne and were previously attributed to flatworms ‘stage, showing some improvement after antiparasitic treatment. In a trial to explore the nature of these ocular lesions among rural Egyptian children, twenty surgically excised ocular lesions were subjected to transmission electron microscopy (TEM) examination. TEM results were combined with previous results of the metagenomic analysis performed for four cases out of the twenty samples, revealing the presence of Toxoplasma gondii (T. gondii), besides, a wide range of microbial communities, including variable species of fungi, bacteria, and archaea. The excised lesions ranged from 1 to 5 mm in size and demonstrated an extensive inflammatory cellular infiltrate. Using TEM, five out of twenty samples revealed active eukaryotic organisms with intact energetic cellular organelles, besides, numerous nuclei encircled within a syncytial layer and enclosed by a hyaline layer rich in mitochondria. Six samples showed inactivity in the cellular and the covering portions, while just inflammatory reaction was seen in the remaining nine samples. Toxoplasma gondii was found free within the distal part of the syncytium while, the proximal part showed the active synthesis of possibly extra polymeric substance, perhaps secreted by the microbial community. In a conclusion, Toxoplasma gondii has been detected among a microbial community in an atypical lesion in the eye. Further studies need to be sustained on genotype characterization, proteomic analysis, besides, the aquatic transmission of these mixed microbial species to the ocular tissues to clarify the reason behind such ocular illness.

The Occurrence of Malignancy in Trypanosoma brucei brucei by Rapid Passage in Mice

Pleomorphic Trypanosoma brucei are best known for their tightly controlled cell growth and developmental program, which ensures their transmissibility and host fitness between the mammalian host and insect vector. However, after long-term adaptation in the laboratory or by natural evolution, monomorphic parasites can be derived. The origin of these monomorphic forms is currently unclear. Here, we produced a series of monomorphic trypanosome stocks by artificially syringe-passage in mice, creating snapshots of the transition from pleomorphism to monomorphism. We then compared these artificial monomorphic trypanosomes, alongside several naturally monomorphic T. evansi and T. equiperdum strains, with the pleomorphic T. brucei. In addition to failing to generate stumpy forms in animal bloodstream, we found that monomorphic trypanosomes from laboratory and nature exhibited distinct differentiation patterns, which are reflected by their distinct differentiation potential and transcriptional changes. Lab-adapted monomorphic trypanosomes could still be induced to differentiate, and showed only minor transcriptional differences to that of the pleomorphic slender forms but some accumulated differences were observed as the passages progress. All naturally monomorphic strains completely fail to differentiate, corresponding to their impaired differentiation regulation. We propose that the natural phenomenon of trypanosomal monomorphism is actually a malignant manifestation of protozoal cells. From a disease epidemiological and evolutionary perspective, our results provide evidence for a new way of thinking about the origin of these naturally monomorphic strains, the malignant evolution of trypanosomes may raise some concerns. Additionally, these monomorphic trypanosomes may reflect the quantitative and qualitative changes in the malignant evolution of T. brucei, suggesting that single-celled protozoa may also provide the most primitive model of cellular malignancy, which could be a primitive and inherent biological phenomenon of eukaryotic organisms from protozoans to mammals.

Chlorosis seedling lethality 1 encoding a MAP3K protein is essential for chloroplast development in rice

Background Mitogen-activated protein kinase (MAPK) cascades are conserved signaling modules in eukaryotic organisms and play essential roles in immunity and stress responses. However, the role of MAPKs in chloroplast development remains to be evidently established. Results In this study, a rice chlorosis seedling lethality 1 (csl1) mutant with a Zhonghua11 (ZH11, japonica) background was isolated. Seedlings of the mutant were characterized by chlorotic leaves and death after the trefoil stage, and chloroplasts were observed to contain accumulated starch granules. Molecular cloning revealed that OsCSL1 encoded a MAPK kinase kinase22 (MKKK22) targeted to the endoplasmic reticulum (ER), and functional complementation of OsCSL1 was found to restore the normal phenotype in csl1 plants. The CRISPR/Cas9 technology was used for targeted disruption of OsCSL1, and the OsCSL1-Cas9 lines obtained therein exhibited yellow seedlings which phenocopied the csl1 mutant. CSL1/MKKK22 was observed to establish direct interaction with MKK4, and altered expression of MKK1 and MKK4 was detected in the csl1 mutant. Additionally, disruption of OsCSL1 led to reduced expression of chloroplast-associated genes, including chlorophyll biosynthetic genes, plastid-encoded RNA polymerases, nuclear-encoded RNA polymerase, and nuclear-encoded chloroplast genes. Conclusions The findings of this study revealed that OsCSL1 played roles in regulating the expression of multiple chloroplast synthesis-related genes, thereby affecting their functions, and leading to wide-ranging defects, including chlorotic seedlings and severely disrupted chloroplasts containing accumulated starch granules.

Extremely Acidic Eukaryotic (Micro) Organisms: Life in Acid Mine Drainage Polluted Environments—Mini-Review

Acid Mine Drainage (AMD) results from sulfide oxidation, which incorporates hydrogen ions, sulfate, and metals/metalloids into the aquatic environment, allowing fixation, bioaccumulation and biomagnification of pollutants in the aquatic food chain. Acidic leachates from waste rock dams from pyritic and (to a lesser extent) coal mining are the main foci of Acid Mine Drainage (AMD) production. When AMD is incorporated into rivers, notable changes in water hydro-geochemistry and biota are observed. There is a high interest in the biodiversity of this type of extreme environments for several reasons. Studies indicate that extreme acid environments may reflect early Earth conditions, and are thus, suitable for astrobiological experiments as acidophilic microorganisms survive on the sulfates and iron oxides in AMD-contaminated waters/sediments, an analogous environment to Mars; other reasons are related to the biotechnological potential of extremophiles. In addition, AMD is responsible for decreasing the diversity and abundance of different taxa, as well as for selecting the most well-adapted species to these toxic conditions. Acidophilic and acidotolerant eukaryotic microorganisms are mostly composed by algae (diatoms and unicellular and filamentous algae), protozoa, fungi and fungi-like protists, and unsegmented pseudocoelomata animals such as Rotifera and micro-macroinvertebrates. In this work, a literature review summarizing the most recent studies on eukaryotic organisms and micro-organisms in Acid Mine Drainage-affected environments is elaborated.

The Fission Yeast Cell Integrity Pathway: A Functional Hub for Cell Survival upon Stress and Beyond

The survival of eukaryotic organisms during environmental changes is largely dependent on the adaptive responses elicited by signal transduction cascades, including those regulated by the Mitogen-Activated Protein Kinase (MAPK) pathways. The Cell Integrity Pathway (CIP), one of the three MAPK pathways found in the simple eukaryote fission of yeast Schizosaccharomyces pombe, shows strong homology with mammalian Extracellular signal-Regulated Kinases (ERKs). Remarkably, studies over the last few decades have gradually positioned the CIP as a multi-faceted pathway that impacts multiple functional aspects of the fission yeast life cycle during unperturbed growth and in response to stress. They include the control of mRNA-stability through RNA binding proteins, regulation of calcium homeostasis, and modulation of cell wall integrity and cytokinesis. Moreover, distinct evidence has disclosed the existence of sophisticated interplay between the CIP and other environmentally regulated pathways, including Stress-Activated MAP Kinase signaling (SAPK) and the Target of Rapamycin (TOR). In this review we present a current overview of the organization and underlying regulatory mechanisms of the CIP in S. pombe, describe its most prominent functions, and discuss possible targets of and roles for this pathway. The evolutionary conservation of CIP signaling in the dimorphic fission yeast S. japonicus will also be addressed.

Genome-Scale Metabolic Modeling Enables In-Depth Understanding of Big Data

Genome-scale metabolic models (GEMs) enable the mathematical simulation of the metabolism of archaea, bacteria, and eukaryotic organisms. GEMs quantitatively define a relationship between genotype and phenotype by contextualizing different types of Big Data (e.g., genomics, metabolomics, and transcriptomics). In this review, we analyze the available Big Data useful for metabolic modeling and compile the available GEM reconstruction tools that integrate Big Data. We also discuss recent applications in industry and research that include predicting phenotypes, elucidating metabolic pathways, producing industry-relevant chemicals, identifying drug targets, and generating knowledge to better understand host-associated diseases. In addition to the up-to-date review of GEMs currently available, we assessed a plethora of tools for developing new GEMs that include macromolecular expression and dynamic resolution. Finally, we provide a perspective in emerging areas, such as annotation, data managing, and machine learning, in which GEMs will play a key role in the further utilization of Big Data.

Evolution of B Chromosomes: From Dispensable Parasitic Chromosomes to Essential Genomic Players

B chromosomes represent additional chromosomes found in many eukaryotic organisms. Their origin is not completely understood but recent genomic studies suggest that they mostly arise through rearrangements and duplications from standard chromosomes. They can occur in single or multiple copies in a cell and are usually present only in a subset of individuals in the population. Because B chromosomes frequently show unstable inheritance, their maintenance in a population is often associated with meiotic drive or other mechanisms that increase the probability of their transmission to the next generation. For all these reasons, B chromosomes have been commonly considered to be nonessential, selfish, parasitic elements. Although it was originally believed that B chromosomes had little or no effect on an organism’s biology and fitness, a growing number of studies have shown that B chromosomes can play a significant role in processes such as sex determination, pathogenicity and resistance to pathogens. In some cases, B chromosomes became an essential part of the genome, turning into new sex chromosomes or germline-restricted chromosomes with important roles in the organism’s fertility. Here, we review such cases of “cellular domestication” of B chromosomes and show that B chromosomes can be important genomic players with significant evolutionary impact.

Designing a Genetic Screen to Identify Factors Required for Meiotic Nuclear Rejuvenation

During the natural cycle of life, most eukaryotic organisms grow old, age, and die. A common natural mechanism by which organisms “reset” their lifespan is through sexual reproduction; however, how this rejuvenation takes place remains unknown. My lab has found that meiosis in budding yeast, the developmental program that forms sex cells, eliminates age-induced damage. This involves the formation of a novel nuclear compartment, the Gametogenesis Uninherited Nuclear Compartment (GUNC), which acts as a trash can for accumulated age-induced damage. To understand the molecular details of this process, I worked on designing a screen for genes involved in GUNC formation. My mentor and I fused three different proteins targeted to the GUNC and a protein that is able to bind to a drug-resistance plasmid, in order to couple the inheritance of a selectable DNA marker with the elimination of age-induced damage. Initial testing of these three fusion proteins suggested that they were unable to successfully target the plasmid to the GUNC; as such, testing of additional candidate proteins is necessary. We plan to eventually use this system to identify mutations that disrupt GUNC formation and cause inheritance of the drug-resistance plasmid. By identifying and perturbing proteins involved in GUNC formation, we are hoping to be able to drive the inheritance of specific types of age-induced damage, allowing for the determination of what a symptom versus a cause of aging is.

Coupling DNA Replication and Spindle Function in Saccharomyces cerevisiae

In the yeast Saccharomyces cerevisiae DNA replication and spindle assembly can overlap. Therefore, signaling mechanisms modulate spindle dynamics in order to ensure correct timing of chromosome segregation relative to genome duplication, especially when replication is incomplete or the DNA becomes damaged. This review focuses on the molecular mechanisms that coordinate DNA replication and spindle dynamics, as well as on the role of spindle-dependent forces in DNA repair. Understanding the coupling between genome duplication and spindle function in yeast cells can provide important insights into similar processes operating in other eukaryotic organisms, including humans.

Global Characterization of XRN 5′-3′ Exoribonucleases and Their Responses to Environmental Stresses in Plants

The XRN family of 5′-3′ Exoribonucleases is functionally conserved in eukaryotic organisms. However, the molecular evolution of XRN proteins in plants and their functions in plant response to environment stresses remain largely unexplored. In this study, we identified 23 XRN proteins in 6 representative plant species. Polygenetic analysis revealed that XRN2 was Arabidopsis-specific among these species, and additional branches outside the clades of XRN3 and XRN4 proteins, which we named as XRN5, were found in rice, maize, and soybean. However, XRN5 in soybean lost their entire 5′-3′ XRN Exoribonuclease domain. Protein conserved sequence analysis showed that XRN3/XRN2 contained potential bipartite nuclear-localization signals (NLS) while all the XRN4 proteins lost their second KR/RR motif of NLS, potentially leading to their cytoplasm localization. SIXRN3-2 contained one mutation in this second KR/RR motif, which may change their sub-cellular localization. The promoter cis-element analysis indicated that these XRN genes responded to multiple stresses and plant hormones diversely at transcriptional level. Finally, transcriptomic analysis suggested that OsXRN3 and ZmXRN3-1 were induced by low temperature, SIXRN4 and ZmXRN4 was inhibited by heat shock, and OsXRN5 and GmXRN5-2 were repressed by drought. However, in general, the expression patterns revealed the response diversity of XRNs to environment stimuli in different plant species. Taken together, this study characterized 23 XRNs with NLS variation that contributed to their sub-cellular localization and provided an overview of the XRNs response diversity to multiple environmental stresses, suggesting that XRNs could be used as potential gene editing candidates for precise stress-tolerant crop breeding.