scholarly journals Comparative genomics of bdelloid rotifers: evaluating the effects of asexuality and desiccation tolerance on genome evolution

2017 ◽  
Author(s):  
Reuben W. Nowell ◽  
Pedro Almeida ◽  
Christopher G. Wilson ◽  
Thomas P. Smith ◽  
Diego Fontaneto ◽  
...  
Keyword(s):  
Genome Evolution ◽  
Desiccation Tolerance ◽  
Unique Feature ◽  
Genome Sequences ◽  
Genomic Features ◽  
Bdelloid Rotifers ◽  
Freshwater Habitats ◽  
Animal Phyla

AbstractBdelloid rotifers are microscopic invertebrates that have existed for millions of years apparently without sex or meiosis. They inhabit a variety of temporary and permanent freshwater habitats globally, and many species are remarkably tolerant of desiccation. Bdelloids offer an opportunity to better understand the evolution of sex and recombination, but previous work has emphasized desiccation as the cause of several unusual genomic features in this group. Here, we evaluate the relative effects of asexuality and desiccation tolerance on genome evolution by comparing whole genome sequences for three bdelloid species: Adineta ricciae (desiccation tolerant), Rotaria macrura and Rotaria magnacalcarata (both desiccation intolerant) to the only published bdelloid genome to date, that of Adineta vaga (also desiccation tolerant). We find that tetraploidy is conserved among all four bdelloid species, but homologous divergence in obligately aquatic Rotaria genomes is low, well within the range observed between alleles in obligately sexual, diploid animals. In addition, we find that homologous regions in A. ricciae are largely collinear and do not form palindromic repeats as observed in the published A. vaga assembly. These findings are contrary to current understanding of the role of desiccation in shaping the bdelloid genome, and indicate that various features interpreted as genomic evidence for long-term ameiotic evolution are not general to all bdelloid species, even within the same genus. Finally, we substantiate previous findings of high levels of horizontally transferred non-metazoan genes encoded in both desiccating and non-desiccating bdelloid species, and show that this is a unique feature of bdelloids among related animal phyla. Comparisons within bdelloids and to other desiccation-tolerant animals, however, again call into question the purported role of desiccation in horizontal transfer.

scholarly journals Spatial and temporal escape from fungal parasitism in natural communities of anciently asexual bdelloid rotifers

2013 ◽  
Vol 280 (1765) ◽  
pp. 20131255 ◽  
Author(s):  
Christopher G. Wilson ◽  
Paul W. Sherman
Keyword(s):  
Field Experiments ◽  
Life Stage ◽  
Red Queen Hypothesis ◽  
Bdelloid Rotifers ◽  
Antagonistic Coevolution ◽  
Freshwater Habitats ◽  
Spatio Temporal ◽  
The Red Queen ◽  
Natural Communities

Sexual reproduction is costly, but it is nearly ubiquitous among plants and animals, whereas obligately asexual taxa are rare and almost always short-lived. The Red Queen hypothesis proposes that sex overcomes its costs by enabling organisms to keep pace with coevolving parasites and pathogens. If so, the few cases of stable long-term asexuality ought to be found in groups whose coevolutionary interactions with parasites are unusually weak. In theory, antagonistic coevolution will be attenuated if hosts disperse among patches within a metapopulation separately from parasites and more rapidly. We examined whether these conditions are met in natural communities of bdelloid rotifers, one of the longest-lived asexual lineages. At any life stage, these microscopic invertebrates can tolerate the complete desiccation of their ephemeral freshwater habitats, surviving as dormant propagules that are readily carried by the wind. In our field experiments, desiccation and wind transport enabled bdelloids to disperse independently of multiple fungal parasites, in both time and space. Surveys of bdelloid communities in unmanipulated moss patches confirmed that fungal parasitism was negatively correlated with extended drought and increasing height (exposure to wind). Bdelloid ecology therefore matches a key condition of models in which asexuals persist through spatio-temporal decoupling from coevolving enemies.

scholarly journals Collagen IV and basement membrane at the evolutionary dawn of metazoan tissues

eLife ◽  
2017 ◽  
Vol 6 ◽  
Author(s):  
Aaron L Fidler ◽  
Carl E Darris ◽  
Sergei V Chetyrkin ◽  
Vadim K Pedchenko ◽  
Sergei P Boudko ◽  
...  
Keyword(s):  
Basement Membrane ◽  
Collagen Iv ◽  
Cellular Microenvironment ◽  
Genomic Features ◽  
Animal Phyla ◽  
Bilaterian Animal ◽  
Extracellular Microenvironment ◽  
Evolutionary Role ◽  
Architectural Unit

The role of the cellular microenvironment in enabling metazoan tissue genesis remains obscure. Ctenophora has recently emerged as one of the earliest-branching extant animal phyla, providing a unique opportunity to explore the evolutionary role of the cellular microenvironment in tissue genesis. Here, we characterized the extracellular matrix (ECM), with a focus on collagen IV and its variant, spongin short-chain collagens, of non-bilaterian animal phyla. We identified basement membrane (BM) and collagen IV in Ctenophora, and show that the structural and genomic features of collagen IV are homologous to those of non-bilaterian animal phyla and Bilateria. Yet, ctenophore features are more diverse and distinct, expressing up to twenty genes compared to six in vertebrates. Moreover, collagen IV is absent in unicellular sister-groups. Collectively, we conclude that collagen IV and its variant, spongin, are primordial components of the extracellular microenvironment, and as a component of BM, collagen IV enabled the assembly of a fundamental architectural unit for multicellular tissue genesis.

scholarly journals How big is the iceberg of which organellar genes in nuclear genomes are but the tip?

2003 ◽  
Vol 358 (1429) ◽  
pp. 39-58 ◽  
Author(s):  
W. F. Doolittle ◽  
Y. Boucher ◽  
C. L. NesbØ ◽  
C. J. Douady ◽  
J. O. Andersson ◽  
...  
Keyword(s):  
Gene Transfer ◽  
Lateral Gene Transfer ◽  
Archaeal Genome ◽  
Genome Sequences ◽  
History Of ◽  
Nuclear Genomes

As more and more complete bacterial and archaeal genome sequences become available, the role of lateral gene transfer (LGT) in shaping them becomes more and more clear. Over the long term, it may be the dominant force, affecting most genes in most prokaryotes. We review the history of LGT, suggesting reasons why its prevalence and impact were so long dismissed. We discuss various methods purporting to measure the extent of LGT, and evidence for and against the notion that there is a core of never–exchanged genes shared by all genomes, from which we can deduce the ‘true’ organismal tree. We also consider evidence for, and implications of, LGT between prokaryotes and phagocytic eukaryotes.

Abusive head trauma (AHT) outcome at long-term follow-up and the role of elective neurosurgical approach: A report of 22 cases

2013 ◽  
Author(s):  
Francesca Menegazzo ◽  
Melissa Rosa Rizzotto ◽  
Martina Bua ◽  
Luisa Pinello ◽  
Elisabetta Tono ◽  
...  
Keyword(s):  
Head Trauma ◽  
Abusive Head Trauma ◽  
Long Term Follow Up

The Second Start of Transformation in Ukraine?

2014 ◽  
pp. 30-52 ◽  
Author(s):  
L. Grigoryev ◽  
E. Buryak ◽  
A. Golyashev
Keyword(s):  
Economic Growth ◽  
Armed Conflict ◽  
Political Crisis ◽  
Investment Climate ◽  
Institutional Reforms ◽  
Personal Consumption ◽  
Governance Quality ◽  
Political Turmoil

The Ukrainian socio-economic crisis has been developing for years and resulted in the open socio-political turmoil and armed conflict. The Ukrainian population didn’t meet objectives of the post-Soviet transformation, and people were disillusioned for years, losing trust in the state and the Future. The role of workers’ remittances in the Ukrainian economy is underestimated, since the personal consumption and stability depend strongly on them. Social inequality, oligarchic control of key national assets contributed to instability as well as regional disparity, aggravated by identity differences. Economic growth is slow due to a long-term underinvestment, and prospects of improvement are dependent on some difficult institutional reforms, macro stability, open external markets and the elites’ consensus. Recovering after socio-economic and political crisis will need not merely time, but also governance quality improvement, institutions reform, the investment climate revival - that can be attributed as the second transformation in Ukraine.

Thoughts on the Long-Term Strategy, Science and Democracy

2006 ◽  
pp. 4-19 ◽  
Author(s):  
L. Abalkin
Keyword(s):  
Strategy Development ◽  
Russian Science ◽  
Global Trends ◽  
The World ◽  
World Development ◽  
Crucial Condition

The article covers unified issues of the long-term strategy development, the role of science as well as democracy development in present-day Russia. The problems of budget proficit, the Stabilization Fund issues, implementation of the adopted national projects, an increasing role of regions in strengthening the integrity and prosperity of the country are analyzed. The author reveals that the protection of businessmen and citizens from the all-embracing power of bureaucrats is the crucial condition of democratization of the society. Global trends of the world development and expert functions of the Russian science are presented as well.

Development of Social and Economic Forecasting and Ideas of A. Anchishkin

2013 ◽  
pp. 143-155
Author(s):  
A. Klepach ◽  
G. Kuranov
Keyword(s):  
Economic Planning ◽  
Special Role ◽  
Economic Management ◽  
Economic Forecasting ◽  
Russian Economy ◽  
World Economic ◽  
Long Term Forecasting ◽  
Working Out

The role of the prominent Soviet economist, academician A. Anchishkin (1933—1987), whose 80th birth anniversary we celebrate this year, in the development of ideas and formation of economic forecasting in the country at the time when the directive planning acted as a leading tool of economic management is explored in the article. Besides, Anchishkin’s special role is noted in developing a comprehensive program of scientific and technical progress, an information basis for working out long-term forecasts of the country’s development, moreover, his contribution to the creation of long-term forecasting methodology and improvement of the statistical basis for economic analysis and economic planning. The authors show that social and economic forecasting in the period after 1991, which has undertaken a number of functions of economic planning, has largely relied on further development of Anchishkin’s ideas, at the same time responding to new challenges for the Russian economy development during its entry into the world economic system.

Sign in / Sign up

Export Citation Format

Share Document