Role of viruses in biosphere

<p>Presented work is synthesis of both literature data and own efforts on study of virus transduction and demography models. The aim would be considering of viruses and other sub-cell organisms as needful part of life on Earth basing on fundamental biology and ecology. It is important to understand the negative consequences for humanity and the biosphere of extreme outbreaks of dangerous viruses (Spanish flu, AIDS, etc.). Viruses were discovered by the Russian scientist D. Ivanovsky in 1892 and named "filtering virus". Having the size of a molecule, it passes freely through filters and masks. In the early twentieth century, the Russian scientist V. Vernadsky predicted the existence of a single information field of the biosphere. In 60-s of XX century was opened to the genetic code, which was uniform in all organisms (G. Korana, etc.). 70-ies the phenomenon of "horizontal transfer," i.e., transferability of information among all living organisms on the planet without a sexual process (B. McClintock, M. Golubovsky, etc.) was discovered. Some viruses (e.g. T4) are the most studied organisms on Earth due to its relative simplicity. The number of virus types is not estimated, but can be measured in millions. The number of virus individuals on the planet is estimated at 10<sup>39</sup>. Viruses are a necessary part of the biosphere. They create a "biological Internet" in which the information unity of organisms is ensured by the constant transfer of DNA sections between all organisms due to vires transduction. Viral epidemics are an example of co-evolution of higher and lower organisms. It temporarily reduces the number of individual species (for example, the number of people during the Spanish flu decreased by 17 million), but never threatens the existence of a particular species. Just as the medical fight against viruses reduces their population, but does not completely destroy them. The human immune system and the virus gene pool are also in a state of co-evolution. The temporary reduction in the number of the host organism of the virus is further compensated by increased immunity and a rise in the birth rate. Viruses activate the immune system of both individuals and humanity as a whole. Man needs them just as small wars are needed to maintain the combat capability of armies. Forecast of negative and positive consequences of virus reproduction is possible basing of modern mathematical ecology and genetics.</p>

Morphogenesis of the Ciliature During Sexual Process of Conjugation in the Ciliated Protist Euplotes raikovi

Morphogenesis is an important process that widely occurs in almost all the organisms, including the ciliated protists. Ciliates are a large group of single-celled eukaryotes that can reproduce asexually (e.g., binary fission) and perform sexual process (e.g., conjugation). Morphogenesis happens in both asexual reproduction and sexual process in ciliates and the reorganization during conjugation is more complex. However, studies of morphogenesis focusing on conjugation are very limited. Here we studied the morphogenetic process during conjugation in the marine species Euplotes raikovi Agamaliev, 1966. The results indicate that: (1) the ciliature in the ventral side reorganizes twice during sexual process, i.e., conjugational and postconjugational reorganization; (2) the adoral zone of membranelles (AZM) is generated de novo in a pouch beneath the cortex during both reorganizations, with the anterior part generated during the first reorganization, while the posterior part formed during the second reorganization; (3) the frontoventral-transverse (FVT) cirri anlagen are formed de novo in both processes with the fragmentation pattern of 2:2:3:3:2; (4) one left marginal cirrus is generated de novo during both reorganizations; and (5) the dorsal ciliature remains intact during the whole process, except that the two caudal cirri originate from the end of the right-most two dorsal kineties during both reorganizations. Comparisons of the morphogenetic process during conjugation demonstrate a considerably stable pattern within Euplotes while the patterns vary dramatically among different ciliate groups.

The effect of sodium thiosulfate in a culture medium on the sexual reproduction of three species of Bacillariophyta

It was studied the effect of sulfur in the form of sodium thiosulfate pentahydrate on the capability of clonal cultures of Pleurosigma sp., Toxarium undulatum, Pseudo-nitzschia calliantha to interbreed successfully and produce fertile offspring if they were cultivated in artificially prepared marine water (ESAW medium). Differences in the time of the beginning of the sexual process and the intensity of its passage for clones contained on ESAW with the addition of sodium thiasulfate and in the absence of it are shown.

Polyphyletic origin, intracellular invasion, and meiotic genes in the putatively asexual agamococcidians (Apicomplexa incertae sedis)

Agamococcidians are enigmatic and poorly studied parasites of marine invertebrates with unexplored diversity and unclear relationships to other sporozoans such as the human pathogens Plasmodium and Toxoplasma. It is believed that agamococcidians are not capable of sexual reproduction, which is essential for life cycle completion in all well studied parasitic apicomplexans. Here, we describe three new species of agamococcidians belonging to the genus Rhytidocystis. We examined their cell morphology and ultrastructure, resolved their phylogenetic position by using near-complete rRNA operon sequences, and searched for genes associated with meiosis and oocyst wall formation in two rhytidocystid transcriptomes. Phylogenetic analyses consistently recovered rhytidocystids as basal coccidiomorphs and away from the corallicolids, demonstrating that the order Agamococcidiorida Levine, 1979 is polyphyletic. Light and transmission electron microscopy revealed that the development of rhytidocystids begins inside the gut epithelial cells, a characteristic which links them specifically with other coccidiomorphs to the exclusion of gregarines and suggests that intracellular invasion evolved early in the coccidiomorphs. We propose a new superorder Eococcidia for early coccidiomorphs. Transcriptomic analysis demonstrated that both the meiotic machinery and oocyst wall proteins are preserved in rhytidocystids. The conservation of meiotic genes and ultrastructural similarity of rhytidocystid trophozoites to macrogamonts of true coccidians point to an undescribed, cryptic sexual process in the group.

Multiple Sex-Specific Differences in the Regulation of Meiotic Progression in C. elegans

ABSTRACTMeiosis is a highly conserved sexual process, yet significant differences exist between males and females in meiotic regulation in many species. Meiotic progression in C. elegans males proceeds more rapidly than female meiosis, suggesting that female meiotic regulation may be more stringent than in males. We have identified multiple differences in the regulation of synapsis, including a difference that suggests the presence of a female-specific meiotic checkpoint that senses the proper initiation of synapsis. This checkpoint is detected by sex differences in the targeting of histone H3 lysine 9 dimethylation (H3K9me2) to unsynapsed chromatin. During oogenic meiosis in hermaphrodites, the failure to initiate synapsis leads to failure to target H3K9me2 enrichment on unsynapsed chromosomes. Loss of the pachytene checkpoint does not reintroduce H3K9me2 enrichment in hermaphrodites, indicating these checkpoints are separable. In contrast, widespread H3K9me2 enrichment occurs as a result of loss of synapsis initiation in both male meiosis and during spermatogenic meiosis in larval XX hermaphrodites. Additionally, male synapsis is insensitive to loss of the dynein motor light chain DLC-1 and to elevated temperatures, whereas female synapsis is prevented by both conditions. We also show that loss of spindle assembly checkpoint proteins, which provide a kinetic barrier to meiotic progression and are required for DLC-1-dependent synapsis phenotypes in hermaphrodites, does not speed up the rate of synapsis in spermatogenic meiosis. These results indicate that meiosis proceeds more rapidly in males because males lack barriers to meiotic progression that are activated by defective synapsis initiation in females.

Estimation of the propensity for sexual selection in a cyclical parthenogen

Cyclical parthenogenesis is a widespread reproductive strategy in which organisms go through one or multiple rounds of clonal reproduction before sexual reproduction. Because sexual reproduction is typically less common than parthenogenesis in populations of the planktonic cladoceran Daphnia magna, it is not frequently studied. Here we examine the sexual process of D. magna and its relation to sexual selection in Daphnia rockpool populations by observing natural mating in these shallow habitats where sex generally occurs throughout the summer. Although microsatellite markers were found to reveal no evidence of disassortative mating or, thus, of inbreeding avoidance, body length and infection status did reveal assortative mating, suggesting sexual selection to act. When two males mated with a single female, the larger male was observed to remain longer, possibly giving it an advantage in sperm competition. Indirect evidence points at the brood pouch as the likely site of fertilization and thus, sperm competition. Sperm length was as variable within ejaculates as it was among males from different populations. Our data provide firm evidence that sexual selection is present in this species, most likely manifesting itself through a combination of female choice and male–male competition.

Conjugation in Euplotes raikovi (Protista, Ciliophora): New Insights into Nuclear Events and Macronuclear Development from Micronucleate and Amicronucleate Cells

Ciliates form a distinct group of single-celled eukaryotes that host two types of nuclei (micro and macronucleus) in the same cytoplasm and have a special sexual process known as conjugation, which involves mitosis, meiosis, fertilization, nuclear differentiation, and development. Due to their high species diversity, ciliates have evolved different patterns of nuclear events during conjugation. In the present study, we investigate these events in detail in the marine species Euplotes raikovi. Our results indicate that: (i) conjugation lasts for about 50 h, the longest stage being the development of the new macronucleus (ca. 36 h); (ii) there are three prezygotic micronuclear divisions (mitosis and meiosis I and II) and two postzygotic synkaryon divisions; and (iii) a fragment of the parental macronucleus fuses with the new developing macronucleus. In addition, we describe for the first time conjugation in amicronucleate E. raikovi cells. When two amicronucleate cells mate, they separate after about 4 h without evident nuclear changes; when one amicronucleate cell mates with a micronucleate cell, the micronucleus undergoes regular prezygotic divisions to form migratory and stationary pronuclei, but the two pronuclei fuse in the same cell. In the amicronucleate cell, the parental macronucleus breaks into fragments, which are then recovered to form a new functional macronucleus. These results add new information on the process of conjugation in both micronucleate and amicronucleate Euplotes cells.

Sexual reproduction of Entomoneis cf. paludosa (Bacillariophyta)

Sexual reproduction and the life cycle of the marine pennate diatom Entomoneis cf. paludosa are described. The reproduction in this species is characterized by morphological and behavioral isogamy. Two gametangia are involved in the sexual process, each of which produces two gametes.

Is the type of sexual process a generic characteristic?

The study of sexual reproduction in members of the pennate diatoms of the genus Haslea (H. ostrearia, H. karadagensis, H. provincialis, H. crucigera, H. subagnita) showed that they all have the same type of sexual reproduction. Our and literature data suggest that the scheme of the process of sexual reproduction is a conservative generic characteristic.