Vegetative Division Research Articles

Variation and correlation between the parameters of the bulbs of the Oriental hyacinth and the amount of precipitation

The area of the Oriental hyacinth is located in the Mediterranean dry subtropical climate zone, with dry summers and rainy winters. The Mediterranean region is characterized by an average monthly temperature of 20-25 °C in summer, 5-12 °C in winter, and an average rainfall of 400-600 mm per year. A long period of drought contributed to the formation of a special life form in the oriental hyacinth – bulbous geophyte. Despite growing in a warm subtropical climate, hyacinth belongs to cold-resistant ephemeroids, which allows it to undergo primary introduction in the temperate continental climate of the Republic of Mari El. The main method of reproduction of hyacinth, within its natural range, is vegetative division, with the formation of daughter bulbs. In natural habitat, the coefficient of vegetative reproduction is influenced by air temperature and precipitation during the active growing season. The purpose of the work was to identify the dependence of the productivity of the Oriental hyacinth on the amount of precipitation in the conditions of the Republic of Mari El. Work on the identification of dependencies was carried out in the period 2012-2015 in the open ground of the botanical garden-Institute of the State Technical University of Yoshkar-Ola. During the work, biometric parameters such as the diameter and height of the bulb, as well as the number of bulbs in one nest, were taken into account. As a result of the work carried out, it was revealed that: the level of individual variability in bulb diameter in most varieties of oriental hyacinth is included in the norm of variation, this indicates the suitability of environmental factors of the region of introduction for this parameter; the number of daughter bulbs in the nest is characterized by a high level of variability and depends on environmental conditions; the reproduction coefficient of hyacinth varieties is strongly influenced such an environmental factor as the amount of precipitation during the growing season (66.7% – 73.7%). The identification of dependencies between the amount of precipitation and the productivity of vegetative reproduction, in the conditions of the Republic of Mari El, will allow us to assess the effectiveness of the primary introduction of Oriental hyacinth. The obtained data can be used in the development of agricultural techniques for growing Oriental hyacinth in conditions of introduction.

Preprint Highlight: Hyphal compartmentalization and sporulation in Streptomyces require the conserved cell division protein SepX.

Most bacteria undergo binary division. Streptomyces, filamentous soil bacteria with a multicellular life cycle, have two functionally distinct modes of cell division: vegetative cross-wall formation and sporulation septation. Although sporulation septation is an important survival strategy, the physiological significance of cross-wall formation remains largely unknown. Using genetics and quantitative imaging, the authors identified a previously uncharacterized protein, SepX, essential for cross-wall formation and for efficient sporulation septation. Deletion of sepX caused severe growth defects, demonstrating the necessity for vegetative division. These results provide a genetic basis for future research into the regulation of bacterial multicellular development, including how cross-walls form, how they relate to fitness, and how the two distinct cell types are coordinated.

Morphology and molecular phylogeny of Bindiferia gen. nov. (Dinophyceae), a new marine, sand-dwelling dinoflagellate genus formerly classified within Amphidinium

ABSTRACT As historically described, the genus Amphidinum has long been recognized to be polyphyletic. Amphidinium sensu lato is the most diverse of all marine benthic dinoflagellate genera and after the redefinition of the sensu stricto genus about 100 species remained of unknown generic affiliation. A species similar to the Australian sensu lato species Amphidinium boggayum was discovered in France. Morphological and molecular phylogenetic data supported the description of a new species and the classification of the two closely related species within a new athecate, photosynthetic, benthic genus, named Bindiferia. Cells were dorsoventrally flattened with smaller asymmetric epicone. The cingulum was descending. The sulcus reached the antapex and had an extension onto the epicone. The apical structure complex formed an anticlockwise loop around the apex. A red stigma was located in the anterior part of the epicone, near the apex. Vegetative division occurred in a non-motile stage within a hyaline sheath. Non-motile cells had dorsal hypocone grooves. The two species differed from each other in epicone size, cingulum displacement, nucleus location and surface groove occurrence. The molecular phylogenetic results showed that Bindiferia is a distinct taxon that is only distantly related to Amphidinium sensu stricto. The nearest sister group to Bindiferia could not be reliably determined, but the apical structure complex suggested a close relationship to the genera of the Gymnodinium sensu stricto clade.

Pathogenic characteristics of intracellular infection in chlamydiosis

This review analyzes scientific data and systematized information regarding microbiological aspects and pathogenesis of chlamydia infection. Chlamydia are obligate intracellular microorganisms that are sensitive to any human cells where energy parasitism is possible: various types of epithelium, fibrocytes, histiocytes, glial and muscle cells, squamous epithelium of the meninges and eyeball, neurons, monocytes, macrophages. Structure, chemical composition and enzymatic activity of Chlamydia closely resemble those in Gram-negative bacteria, as they retain their morphological identity throughout the life cycle, possess cell wall, ribosomes, DNA, RNA, biochemical elements of glycolysis, tissue respiration, peptose production being sensitive to some broad-spectrum antibiotics, and are able to vegetative form division. In recent decades, the pathogenesis and clinical symptoms of chlamydial lesions in the urogenital tract, nervous, cardiovascular, musculoskeletal and bronchopulmonary systems have been actively studied, and new approaches and treatment schemes for chlamydia-infected patients are still developing. Over many decades, Chlamydia infection has been an important and urgent problem, not only due to its high prevalence, but also because of high rate of complications negatively affecting populational health and related demographic parameters. Chlamydia causes multiple diseases resulting in chronization of inflammatory process in all human organs and systems, and affects reproduction of population. Mandatory statistical recording of chlamydiosis cases introduced as early as in 1994 in the Russian Federation does not reflect the actual incidence rate. A rise in number of inflammatory diseases of the upper respiratory tract caused by Chlamydia undoubtedly increases its etiological importance, but data regarding etiopathogenetic role of Chlamydia in ENT pathology are ambiguous and contradictory. Available publications describe a large range of variation in rate of detected Chlamydia due to poor awareness of doctors about the microbiological properties of chlamydia, pathogenetic and clinical features of clinical signs of this infection, and lack of common and clear understanding on the algorithms for identifying and treating chlamydiosis. Since the majority of chlamydia-associated nosological forms are asymptomatic, knowing pathogenetic features of related will allow to prevent the spread of the infection and reduce subsequent socio-economic consequences.

The Depth Distribution of Dominant Species of Macrophytes in the Northwestern Part of the Tatar Strait

This paper investigates the depth distribution patterns of bottom vegetation dominants in the western Tatar Strait (within Khabarovsk Krai). Materials were collected during SCUBA diving surveys performed by the Khabarovsk Branch of the Pacific Research Fisheries Center. The vegetation cover, in the presence of suitable bottom substrates, is formed to depths of 18–22 m and is replaced below by sparse settlements. The abundance indices of most of the dominant species remain relatively stable within depths of 2–20 m. Their ecological optima, as a rule, occur at depths of 2–6 m with increased hydrodynamics. A scheme of the vertical division of vegetation in the area is proposed that corresponds to the results of previous studies on phytal zoning. The location of vegetation horizons and strata is not different from those previously identified, while their boundaries are blurred and correspond to the continuous live cover distribution.

Colin Brownlee.

Colin Brownlee.

RNA Sequencing of Stentor Cell Fragments Reveals Transcriptional Changes during Cellular Regeneration

While ciliates of the genus Stentor are known for their ability to regenerate when their cells are damaged or even fragmented, the physical and molecular mechanisms underlying this process are poorly understood. To identify genes involved in the regenerative capability of Stentor cells, RNA sequencing of individual Stentor polymorphus cell fragments was performed. After splitting a cell over the anterior-posterior axis, the posterior fragment has to regenerate the oral apparatus, while the anterior part needs to regenerate the hold fast. Altogether, differential expression analysis of both posterior and anterior S.polymorphus cellfragments for four different post-split time pointsrevealed over 10,000 upregulated genes throughout the regeneration process. Among these, genes involved in cell signaling, microtubule-based movement, and cell cycle regulation seemed to be particularly important during cellular regeneration. We identified roughly nine times as many upregulated genes in regenerating S.polymorphus posterior fragments as compared to anterior fragments, indicating that regeneration of the anterior oral apparatus is a complex process that involves many genes. Our analyses identified several expanded groups of genes, such as dual-specific tyrosine-(Y)-phosphorylation-regulated kinases and MORN domain-containing proteins that seemingly act as key regulators of cellular regeneration. In agreement with earlier morphological and cell biological studies [1, 2], our differential expression analyses indicate that cellular regeneration and vegetative division share many similarities.

Interaction of the Morphogenic Protein RodZ with the Bacillus subtilis Min System.

Vegetative cell division in Bacillus subtilis takes place precisely at the middle of the cell to ensure that two viable daughter cells are formed. The first event in cell division is the positioning of the FtsZ Z-ring at the correct site. This is controlled by the coordinated action of both negative and positive regulators. The existence of positive regulators has been inferred, but none have presently been identified in B. subtilis. Noc and the Min system belong to negative regulators; Noc prevents division from occurring over the chromosomes, and the Min system inhibits cell division at the poles. Here we report that the morphogenic protein, RodZ, an essential cell shape determinant, is also required for proper septum positioning during vegetative growth. In rodZ mutant cells, the vegetative septum is positioned off center, giving rise to small, round, DNA-containing cells. Searching for the molecular mechanism giving rise to this phenotype led us to discover that RodZ directly interacts with MinJ. We hypothesize that RodZ may aid the Min system in preventing non-medial vegetative division.

The Effect of Temperature on Vegetative Growth and Sexual Reproduction of Two Diatoms from the Genus Haslea Simonsen

The effect of temperature on sexual reproduction and the rate of vegetative division were investigated in laboratory experiments with Haslea ostrearia (Gaillon) Simonsen from the Atlantic and H. karadagensis Davidovich, Gastineau et Mouget from the Black Sea. In the range of 10–26°С, a temperature increase was favorable for vegetative growth; the maximum growth rate was recorded at the highest temperature of the range. In contrast to vegetative growth, sexual reproduction of both algal species was effective in the temperature range of 10–18°С, but did not occur at temperatures of 23°С. The optimal temperature for auxosporulation was in H. karadagensis somewhat lower than in H. ostrearia. The determined physiological optimums for sexual reproduction can explain the cell-size distribution that is characteristic of the natural population of H. karadagensis in different seasons of the year.

Genome Dynamics of Hybrid Saccharomyces cerevisiae During Vegetative and Meiotic Divisions.

Mutation and recombination are the major sources of genetic diversity in all organisms. In the baker’s yeast, all mutation rate estimates are in homozygous background. We determined the extent of genetic change through mutation and loss of heterozygosity (LOH) in a heterozygous Saccharomyces cerevisiae genome during successive vegetative and meiotic divisions. We measured genome-wide LOH and base mutation rates during vegetative and meiotic divisions in a hybrid (S288c/YJM789) S. cerevisiae strain. The S288c/YJM789 hybrid showed nearly complete reduction in heterozygosity within 31 generations of meioses and improved spore viability. LOH in the meiotic lines was driven primarily by the mating of spores within the tetrad. The S288c/YJM789 hybrid lines propagated vegetatively for the same duration as the meiotic lines, showed variable LOH (from 2 to 3% and up to 35%). Two of the vegetative lines with extensive LOH showed frequent and large internal LOH tracts that suggest a high frequency of recombination repair. These results suggest significant LOH can occur in the S288c/YJM789 hybrid during vegetative propagation presumably due to return to growth events. The average base substitution rates for the vegetative lines (1.82 × 10−10 per base per division) and the meiotic lines (1.22 × 10−10 per base per division) are the first genome-wide mutation rate estimates for a hybrid yeast. This study therefore provides a novel context for the analysis of mutation rates (especially in the context of detecting LOH during vegetative divisions), compared to previous mutation accumulation studies in yeast that used homozygous backgrounds.

Diatom flagellar genes and their expression during sexual reproduction in Leptocylindrus danicus

BackgroundFlagella have been lost in the vegetative phase of the diatom life cycle, but they are still present in male gametes of centric species, thereby representing a hallmark of sexual reproduction. This process, besides maintaining and creating new genetic diversity, in diatoms is also fundamental to restore the maximum cell size following its reduction during vegetative division. Nevertheless, sexual reproduction has been demonstrated in a limited number of diatom species, while our understanding of its different phases and of their genetic control is scarce.ResultsIn the transcriptome of Leptocylindrus danicus, a centric diatom widespread in the world’s seas, we identified 22 transcripts related to the flagella development and confirmed synchronous overexpression of 6 flagellum-related genes during the male gamete formation process. These transcripts were mostly absent in the closely related species L. aporus, which does not have sexual reproduction. Among the 22 transcripts, L. danicus showed proteins that belong to the Intra Flagellar Transport (IFT) subcomplex B as well as IFT-A proteins, the latter previously thought to be absent in diatoms. The presence of flagellum-related proteins was also traced in the transcriptomes of several other centric species. Finally, phylogenetic reconstruction of the IFT172 and IFT88 proteins showed that their sequences are conserved across protist species and have evolved similarly to other phylogenetic marker genes.ConclusionOur analysis describes for the first time the diatom flagellar gene set, which appears to be more complete and functional than previously reported based on the genome sequence of the model centric diatom, Thalassiosira pseudonana. This first recognition of the whole set of diatom flagellar genes and of their activation pattern paves the way to a wider recognition of the relevance of sexual reproduction in individual species and in the natural environment.

Oscillating behavior of Clostridium difficile Min proteins in Bacillus subtilis

In rod‐shaped bacteria, the proper placement of the division septum at the midcell relies, at least partially, on the proteins of the Min system as an inhibitor of cell division. The main principle of Min system function involves the formation of an inhibitor gradient along the cell axis; however, the establishment of this gradient differs between two well‐studied gram‐negative and gram‐positive bacteria. While in gram‐negative Escherichia coli, the Min system undergoes pole‐to‐pole oscillation, in gram‐positive Bacillus subtilis, proper spatial inhibition is achieved by the preferential attraction of the Min proteins to the cell poles. Nevertheless, when E.coli Min proteins are inserted into B.subtilis cells, they still oscillate, which negatively affects asymmetric septation during sporulation in this organism. Interestingly, homologs of both Min systems were found to be present in various combinations in the genomes of anaerobic and endospore‐forming Clostridia, including the pathogenic Clostridium difficile. Here, we have investigated the localization and behavior of C.difficile Min protein homologs and showed that MinDE proteins of C.difficile can oscillate when expressed together in B.subtilis cells. We have also investigated the effects of this oscillation on B.subtilis sporulation, and observed decreased sporulation efficiency in strains harboring the MinDE genes. Additionally, we have evaluated the effects of C.difficile Min protein expression on vegetative division in this heterologous host.

Identification of the meiotic toolkit in diatoms and exploration of meiosis-specific SPO11 and RAD51 homologs in the sexual species Pseudo-nitzschia multistriata and Seminavis robusta.

BackgroundSexual reproduction is an obligate phase in the life cycle of most eukaryotes. Meiosis varies among organisms, which is reflected by the variability of the gene set associated to the process. Diatoms are unicellular organisms that belong to the stramenopile clade and have unique life cycles that can include a sexual phase.ResultsThe exploration of five diatom genomes and one diatom transcriptome led to the identification of 42 genes potentially involved in meiosis. While these include the majority of known meiosis-related genes, several meiosis-specific genes, including DMC1, could not be identified. Furthermore, phylogenetic analyses supported gene identification and revealed ancestral loss and recent expansion in the RAD51 family in diatoms. The two sexual species Pseudo-nitzschia multistriata and Seminavis robusta were used to explore the expression of meiosis-related genes: RAD21, SPO11-2, RAD51-A, RAD51-B and RAD51-C were upregulated during meiosis, whereas other paralogs in these families showed no differential expression patterns, suggesting that they may play a role during vegetative divisions. An almost identical toolkit is shared among Pseudo-nitzschia multiseries and Fragilariopsis cylindrus, as well as two species for which sex has not been observed, Phaeodactylum tricornutum and Thalassiosira pseudonana, suggesting that these two may retain a facultative sexual phase.ConclusionsOur results reveal the conserved meiotic toolkit in six diatom species and indicate that Stramenopiles share major modifications of canonical meiosis processes ancestral to eukaryotes, with important divergences in each Kingdom.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-015-1983-5) contains supplementary material, which is available to authorized users.

Rapid growth and concerted sexual transitions by a bloom of the harmful dinoflagellate Alexandrium fundyense (Dinophyceae).

Transitions between life cycle stages by the harmful dinoflagellate Alexandrium fundyense are critical for the initiation and termination of its blooms. To quantify these transitions in a single population, an Imaging FlowCytobot (IFCB), was deployed in Salt Pond (Eastham, Massachusetts), a small, tidally flushed kettle pond that hosts near annual, localized A. fundyense blooms. Machine‐based image classifiers differentiating A. fundyense life cycle stages were developed and results were compared to manually corrected IFCB samples, manual microscopy‐based estimates of A. fundyense abundance, previously published data describing prevalence of the parasite Amoebophrya, and a continuous culture of A. fundyense infected with Amoebophrya. In Salt Pond, a development phase of sustained vegetative division lasted approximately 3 weeks and was followed by a rapid and near complete conversion to small, gamete cells. The gametic period (∼3 d) coincided with a spike in the frequency of fusing gametes (up to 5% of A. fundyense images) and was followed by a zygotic phase (∼4 d) during which cell sizes returned to their normal range but cell division and diel vertical migration ceased. Cell division during bloom development was strongly phased, enabling estimation of daily rates of division, which were more than twice those predicted from batch cultures grown at similar temperatures in replete medium. Data from the Salt Pond deployment provide the first continuous record of an A. fundyense population through its complete bloom cycle and demonstrate growth and sexual induction rates much higher than are typically observed in culture.

The observation of plcA mutation and localization in Aspergillus nidulans.

To know the function of the plcA gene, which encodes a putative phosphoinositide-specific phospholipase C, in a model filamentous fungus Aspergillus nidulans, it was disrupted thorough homologous recombination and examined. The germination rate of ΔplcA was reduced by approximately 65% and germination of ΔplcA at a lower temperature (25°C) was much slower than germination under normal conditions (37°C), suggesting the plcA is responsible for cold-sensitivity. The hyphal growth of ΔplcA was slightly reduced at 37°C and conspicuously reduced at 25°C. While germinating ΔplcA formed giant swollen spores, and generated short and thick hyphae. The results of the nuclear examination of ΔplcA showed nuclear division with missegregation, and the rate of nuclear division was lower than that of wild type at both 25°C and 37°C. The results of this study showed that plcA is localized to the nucleus through intracellular calcium signaling in A. nidulans. The abnormal nuclear division, resulting from plcA gene deletion, affects conidiation in asexual development. Taken together, these results suggested that plcA is required for normal vegetative growth, morphogenesis, conidiation, and nuclear division in A. nidulans.

A Quantitative Assessment of the Role of the Parasite Amoebophrya in the Termination of Alexandrium fundyense Blooms within a Small Coastal Embayment

Parasitic dinoflagellates of the genus Amoebophrya infect free-living dinoflagellates, some of which can cause harmful algal blooms (HABs). High prevalence of Amoebophrya spp. has been linked to the decline of some HABs in marine systems. The objective of this study was to evaluate the impact of Amoebophrya spp. on the dynamics of dinoflagellate blooms in Salt Pond (MA, USA), particularly the harmful species Alexandrium fundyense. The abundance of Amoebophrya life stages was estimated 3–7 days per week through the full duration of an annual A. fundyense bloom using fluorescence in situ hybridization coupled with tyramide signal amplification (FISH- TSA). More than 20 potential hosts were recorded including Dinophysis spp., Protoperidinium spp. and Gonyaulax spp., but the only dinoflagellate cells infected by Amoebophrya spp. during the sampling period were A. fundyense. Maximum A. fundyense concentration co-occurred with an increase of infected hosts, followed by a massive release of Amoebophrya dinospores in the water column. On average, Amoebophrya spp. infected and killed ∼30% of the A. fundyense population per day in the end phase of the bloom. The decline of the host A. fundyense population coincided with a dramatic life-cycle transition from vegetative division to sexual fusion. This transition occurred after maximum infected host concentrations and before peak infection percentages were observed, suggesting that most A. fundyense escaped parasite infection through sexual fusion. The results of this work highlight the importance of high frequency sampling of both parasite and host populations to accurately assess the impact of parasites on natural plankton assemblages.

Chlorella sphaerica та її місце у системі роду Diplosphaera (chlorophyta, trebouxiophyceae)

За результатами морфологічного та молекулярно-генетичного аналізів автентичного штаму критичної у таксономічному відношенні зеленої водорості Chlorella sphaerica Tschermak-Woess встановлено її фенотипічну схожість та філогенетичну спорідненість із видами роду Diplosphaera Bialosuknia та суттєву відмінність від інших видів роду Chlorella Bejerink. Виявлено нові морфологічні риси (наявність вегетативного поділу, здатність утворювати діади та пакети, формувати зовнішні слизові структури), які дозволяють розглядати Ch. sphaerica у системі роду Diplosphaera. Результати аналізу некодувальних нуклеотидних послідовностей ITS-1 та ITS-2 кластеру ядерних рибосомальних генів підтверджують цей висновок. На підставі отриманих даних запропоновано нову номенклатурну комбінацію: Diplosphaera sphaerica (Tschermak-Woess) Karbovska et Kostikov, comb. nova (basionym: Chlorella sphaerica Tschermak-Woess).

Phosphatidylinositol phospholipase C mediates carbon sensing and vegetative nuclear duplication rates inAspergillus nidulans

In this work, we disrupted one of three putative phosphatidylinositol phospholipase C genes of Aspergillus nidulans and studied its effect on carbon source sensing linked to vegetative mitotic nuclear division. We showed that glucose does not affect nuclear division rates during early vegetative conidial germination (6-7h) in either the wild type or the plcA-deficient mutant. Only after 8h of cultivation on glucose did the mutant strain present some decrease in nuclear duplication. However, decreased nuclear division rates were observed in the wild type when cultivated in media amended with polypectate, whereas our plcA-deficient mutant did not show slow nuclear duplication rates when grown on this carbon source, even though it requires induction and secretion of multiple pectinolytic enzymes to be metabolized. Thus, plcA appears to be directly linked to high-molecular-weight carbon source sensing.

The Baker's Yeast Diploid Genome Is Remarkably Stable in Vegetative Growth and Meiosis

Accurate estimates of mutation rates provide critical information to analyze genome evolution and organism fitness. We used whole-genome DNA sequencing, pulse-field gel electrophoresis, and comparative genome hybridization to determine mutation rates in diploid vegetative and meiotic mutation accumulation lines of Saccharomyces cerevisiae. The vegetative lines underwent only mitotic divisions while the meiotic lines underwent a meiotic cycle every ∼20 vegetative divisions. Similar base substitution rates were estimated for both lines. Given our experimental design, these measures indicated that the meiotic mutation rate is within the range of being equal to zero to being 55-fold higher than the vegetative rate. Mutations detected in vegetative lines were all heterozygous while those in meiotic lines were homozygous. A quantitative analysis of intra-tetrad mating events in the meiotic lines showed that inter-spore mating is primarily responsible for rapidly fixing mutations to homozygosity as well as for removing mutations. We did not observe 1–2 nt insertion/deletion (in-del) mutations in any of the sequenced lines and only one structural variant in a non-telomeric location was found. However, a large number of structural variations in subtelomeric sequences were seen in both vegetative and meiotic lines that did not affect viability. Our results indicate that the diploid yeast nuclear genome is remarkably stable during the vegetative and meiotic cell cycles and support the hypothesis that peripheral regions of chromosomes are more dynamic than gene-rich central sections where structural rearrangements could be deleterious. This work also provides an improved estimate for the mutational load carried by diploid organisms.

Maintaining Clonal Paramecium tetraurelia Cell Lines of Controlled Age through Daily Reisolation

INTRODUCTIONThe sexual cycle of Paramecium tetraurelia can be managed by controlling food uptake, allowing the study of developmentally regulated differentiation in synchronous cultures. Clonal cell lines can be established easily by single cell isolation and can be grown in bacterized grass infusion medium for a large number of vegetative divisions before entering senescence. Sexual reproduction is triggered by starvation and therefore can be induced or prevented as needed by controlling the availability of food. Given a constant supply of food, P. tetraurelia cells will remain in the vegetative phase of their life cycle and, at 27°C, will divide by binary fission every 6 h. The daily reisolation procedure described here results in populations of P. tetraurelia of known age and produced under reproducible physiological conditions, which can help to standardize experiments. Paramecia produced under these conditions are suitable for immunocytochemical studies or use in genetic cross experiments.