scholarly journals Phytosterol Profiles, Genomes and Enzymes – An Overview

2021 ◽  
Vol 12 ◽  
Author(s):  
Sylvain Darnet ◽  
Aurélien Blary ◽  
Quentin Chevalier ◽  
Hubert Schaller
Keyword(s):  
Analytical Chemistry ◽  
Candidate Genes ◽  
Tree Of Life ◽  
Seed Plants ◽  
Functional Assays ◽  
Unicellular Eukaryotes ◽  
Fast Pace ◽  
Living Organisms ◽  
Taxonomic Groups

The remarkable diversity of sterol biosynthetic capacities described in living organisms is enriched at a fast pace by a growing number of sequenced genomes. Whereas analytical chemistry has produced a wealth of sterol profiles of species in diverse taxonomic groups including seed and non-seed plants, algae, phytoplanktonic species and other unicellular eukaryotes, functional assays and validation of candidate genes unveils new enzymes and new pathways besides canonical biosynthetic schemes. An overview of the current landscape of sterol pathways in the tree of life is tentatively assembled in a series of sterolotypes that encompass major groups and provides also peculiar features of sterol profiles in bacteria, fungi, plants, and algae.

Heterochrony and the Problem of Missing Links in Evolutionary Sequences

1984 ◽  
Vol 1 ◽  
pp. 84-96 ◽  
Author(s):  
Thomas W. Broadhead ◽  
Johnny A. Waters
Keyword(s):  
Natural Selection ◽  
Feature Recognition ◽  
Biological Meaning ◽  
Juvenile Stages ◽  
Transitional Forms ◽  
Living Organisms ◽  
Taxonomic Groups ◽  
Organic Change

Critics of the concept of organic change through time have demanded proof not only of “transitional forms” but of specific transitions among higher taxonomic groups. Transitional forms among species and between a species of one genus and a species of another genus have been criticized because most demonstrated ancestor-descendant transitions are considered to occur within one “kind” of organism; the “kind” concept is bereft of biological meaning.Natural selection acts upon organisms at all stages of ontogeny, and especially at larval-juvenile stages. Large shifts in the morphology of one or more features are common in groups of organisms that evolve by heterochrony. Because heterochrony involves a change in timing of the appearance or development of a particular feature, recognition of heterochrony requires a confident knowledge of ontogeny. The resulting increase in complexity (e.g. recapitulation) or decrease in complexity (e.g. paedomorphosis), well documented among living organisms, commonly excludes morphologic intermediates. Paedomorphosis is especially important in the evolution of progressively simplifying lineages and has been well documented from living plants and animals and fossil representatives of echinoderms (blastoids, crinoids), conodonts, arthropods, mollusks and vertebrates. Heterochrony characterizes the evolution of most metazoan organisms, occurs at all taxonomic levels and was probably responsible for major innovations by which higher taxonomic groups are recognized.

scholarly journals The fractal dimension of the tree of life

2014 ◽  
Author(s):  
Xiaofei Lv ◽  
Yuping Wu ◽  
Bin Ma
Keyword(s):  
Fractal Dimension ◽  
Power Law ◽  
Fractal Dimensions ◽  
Predictive Modelling ◽  
Tree Of Life ◽  
Fundamental Question ◽  
Theoretical Studies ◽  
Structure Pattern ◽  
Intermediate Size ◽  
Taxonomic Groups

The structure pattern of the tree of life clues on the key ecological issues; hence knowing the fractal dimension is the fundamental question in understanding the tree of life. Yet the fractal dimension of the tree of life remains unclear since the scale of the tree of life has hypergrown in recent years. Here we show that the tree of life display a consistent power-law rules for inter- and intra-taxonomic levels, but the fractal dimensions were different among different kingdoms. The fractal dimension of hierarchical structure (Dr) is 0.873 for the entire tree of life, which smaller than the values of Dr for Animalia and Plantae but greater than the values of Dr for Fungi, Chromista, and Protozoa. The hierarchical fractal dimensions values for prokaryotic kingdoms are lower than for other kingdoms. The Dr value for Viruses was lower than most eukaryotic kingdoms, but greater than prokaryotes. The distribution of taxa size is governed by fractal diversity but skewed by overdominating taxa with large subtaxa size. The proportion of subtaxa in taxa with small and large sizes was greater than in taxa with intermediate size. Our results suggest that the distribution of subtaxa in taxa can be predicted with fractal dimension for the accumulating taxa abundance rather than the taxa abundance. Our study determined the fractal dimensions for inter- and intra-taxonomic levels of the present tree of life. These results emphases the need for further theoretical studies, as well as predictive modelling, to interpret the different fractal dimension for different taxonomic groups and skewness of taxa with large subtaxa size.

scholarly journals Revisiting the impacts of non-random extinction on the tree-of-life

2013 ◽  
Vol 9 (4) ◽  
pp. 20130343 ◽  
Author(s):  
T. Jonathan Davies ◽  
Kowiyou Yessoufou
Keyword(s):  
Empirical Data ◽  
Extinction Risk ◽  
Tree Of Life ◽  
Branch Lengths ◽  
Recent Debate ◽  
Conservation Concern ◽  
Living Organisms ◽  
Close Relatives ◽  
The Impact ◽  
Number Of Branches

The tree-of-life represents the diversity of living organisms. Species extinction and the concomitant loss of branches from the tree-of-life is therefore a major conservation concern. There is increasing evidence indicating that extinction is phylogenetically non-random, such that if one species is vulnerable to extinction so too are its close relatives. However, the impact of non-random extinctions on the tree-of-life has been a matter of recent debate. Here, we combine simulations with empirical data on extinction risk in mammals. We demonstrate that phylogenetically clustered extinction leads to a disproportionate loss of branches from the tree-of-life, but that the loss of their summed lengths is indistinguishable from random extinction. We argue that under a speciational model of evolution, the number of branches lost might be of equal or greater consequences than the loss of summed branch lengths. We therefore suggest that the impact of non-random extinction on the tree-of-life may have been underestimated.

scholarly journals The fractal dimension of the tree of life

2014 ◽  
Author(s):  
Bin Ma ◽  
Xiaofei Lv ◽  
Jun Gong
Keyword(s):  
Fractal Dimension ◽  
Power Law ◽  
Fractal Dimensions ◽  
Predictive Modelling ◽  
Tree Of Life ◽  
Fundamental Question ◽  
Theoretical Studies ◽  
Structure Pattern ◽  
Intermediate Size ◽  
Taxonomic Groups

The structure pattern of the tree of life clues on the key ecological issues; hence knowing the fractal dimension is the fundamental question in understanding the tree of life. Yet the fractal dimension of the tree of life remains unclear since the scale of the tree of life has hypergrown in recent years. Here we show that the tree of life display a consistent power-law rules for inter- and intra-taxonomic levels, but the fractal dimensions were different among different kingdoms. The fractal dimension of hierarchical structure (Dr) is 0.873 for the entire tree of life, which smaller than the values of Dr for Animalia and Plantae but greater than the values of Dr for Fungi, Chromista, and Protozoa. The hierarchical fractal dimensions values for prokaryotic kingdoms are lower than for other kingdoms. The Dr value for Viruses was lower than most eukaryotic kingdoms, but greater than prokaryotes. The distribution of taxa size is governed by fractal diversity but skewed by overdominating taxa with large subtaxa size. The proportion of subtaxa in taxa with small and large sizes was greater than in taxa with intermediate size. Our results suggest that the distribution of subtaxa in taxa can be predicted with fractal dimension for the accumulating taxa abundance rather than the taxa abundance. Our study determined the fractal dimensions for inter- and intra-taxonomic levels of the present tree of life. These results emphases the need for further theoretical studies, as well as predictive modelling, to interpret the different fractal dimension for different taxonomic groups and skewness of taxa with large subtaxa size.

Protozooplankton: Radiolaria

2017 ◽  
Author(s):  
Rowena Stern ◽  
Claire Taylor ◽  
Fabrice Not ◽  
Johan Decelle
Keyword(s):  
Life Cycle ◽  
Tree Of Life ◽  
Lattice Structures ◽  
Unicellular Eukaryotes ◽  
Deep Waters ◽  
Family Level

This chapter describes the taxonomy of radiolaria. Radiolaria are amoeboid unicellular eukaryotes with mineral skeletons, often forming elaborate symmetrical lattice structures with spines. They form an abundant part of marine holoplankton from surface to deep waters. The chapter covers their life cycle, ecology and distribution, and identification. It includes a section that indicates the systematic placement of the taxon described within the tree of life, and lists the key marine representative illustrated in the chapter (usually to genus or family level). This section also provides information on the taxonomic authorities responsible for the classification adopted, recent changes which might have occurred, and lists relevant taxonomic sources.

The content of mercury and lead in the feed base of valuable fish species of the Caspian Sea

Fisheries ◽  
2021 ◽  
Vol 2021 (4) ◽  
pp. 10-14
Author(s):  
Tatiana Ershova ◽  
Vladimir Chaplygin ◽  
Vyacheslav Zaitsev ◽  
Alisher Khursanov ◽  
Natalia Shaboyants
Keyword(s):  
Caspian Sea ◽  
Chemical Elements ◽  
Essential Elements ◽  
The Body ◽  
The Caspian Sea ◽  
Rhithropanopeus Harrisii ◽  
The North ◽  
Living Organisms ◽  
Taxonomic Groups ◽  
High Level

Mercury and lead are not essential elements and have a high degree of toxicity to all groups of living organisms, including hydrobionts. In turn, the accumulation of dangerous chemical elements in the primary trophic units of marine ecosystems is also reflected in the high level of accumulation and toxication of fish-valuable objects of fishing. As part of the study of the ecological state of the biota of the Volga-Caspian basin, there is a need to study the concentrations of heavy metals such as mercury and lead. The aim of the work is to study the content of mercury and lead in some invertebrate species of the Caspian Sea. The main source of mercury and lead in the body of the studied species is the water of the north-western part of the Caspian Sea. Among the studied taxonomic groups of organisms, mercury accumulators were all species of mollusks, as well as Balanus improvises and Rhithropanopeus harrisii. The lead concentrating organisms were Cerastoderma lamarcki and Mytilaster lineatus, Rhithropanopeus harrisii, and Balanus improvises.

scholarly journals Transcriptome Analysis Reveals Docosahexaenoic Acid and α-Linolenic Acid Affect Cholesterol Metabolism and Migration of Monocytes via Common and Distinct Gene Pathways

2021 ◽  
Vol 5 (Supplement_2) ◽  
pp. 948-948
Author(s):  
Lisa Rodway ◽  
Samantha Pauls ◽  
Harold Aukema ◽  
Carla Taylor ◽  
Peter Zahradka
Keyword(s):  
Fatty Acids ◽  
Docosahexaenoic Acid ◽  
Candidate Genes ◽  
Linolenic Acid ◽  
Transcriptome Analysis ◽  
Cholesterol Metabolism ◽  
Cholesterol Content ◽  
Functional Assays ◽  
Monocyte Migration ◽  
And Migration

Abstract Objectives One of the earliest events in atherosclerotic plaque formation is the migration of monocytes to damaged blood vessels, and the accumulation of cholesterol in monocyte-derived macrophages. The omega-3 fatty acid docosahexaenoic acid (DHA) is known to inhibit this process. While there is limited evidence suggesting α-linolenic acid (ALA) has a similar effect, ALA has not been directly compared to DHA. The primary objective of this study was to compare the gene expression profiles of monocytes that have been exposed to either ALA or DHA and examine the effect of these fatty acids on monocyte cholesterol content and migration in a cell culture model. Methods Transcriptome analysis was performed on total mRNA isolated from human THP-1 monocytes treated with ALA, DHA or vehicle for 48 h. Candidate genes identified via fold change and Ingenuity Pathway Analysis were validated by qPCR. Functional assays to measure total cholesterol content and migration were then performed on monocytes treated with ALA or DHA. Results Transcriptome analysis identified a series of genes associated with cholesterol metabolism and cell migration altered by ALA and DHA treatment. Changes in mRNA levels for candidate genes were validated by qPCR, with similar expression patterns as in the transcriptome analysis. Based on these data, both fatty acids were predicted to reduce cholesterol synthesis, ALA would increase migration and DHA would have no effect. Functional assays were then performed and revealed that ALA and DHA decreased cholesterol content to a similar extent. Additionally, contrary to our predictions, DHA significantly decreased migration, while ALA had no effect. Conclusions The results suggest ALA and DHA may influence monocyte migration through distinct gene pathways, while cholesterol metabolism may be regulated by a common mechanism. Furthermore, only DHA treatment reduced monocyte migration in functional assays, while both fatty acids reduced cholesterol content. Due to the critical role of monocyte migration and cholesterol content in the pathophysiology of atherosclerosis, it may be concluded from this study that both DHA and ALA may exert protective effects involving different mechanisms as they relate to individuals at risk for cardiovascular disease. Funding Sources CIHR, NSERC

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