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. 2015 Sep 26;370(1678):20140331.
doi: 10.1098/rstb.2014.0331.

What's in a genome? The C-value enigma and the evolution of eukaryotic genome content

Tyler A Elliott  1 , T Ryan Gregory  2
Affiliations

What's in a genome? The C-value enigma and the evolution of eukaryotic genome content

Tyler A Elliott et al. Philos Trans R Soc Lond B Biol Sci. .

Abstract

Some notable exceptions aside, eukaryotic genomes are distinguished from those of Bacteria and Archaea in a number of ways, including chromosome structure and number, repetitive DNA content, and the presence of introns in protein-coding regions. One of the most notable differences between eukaryotic and prokaryotic genomes is in size. Unlike their prokaryotic counterparts, eukaryotes exhibit enormous (more than 60,000-fold) variability in genome size which is not explained by differences in gene number. Genome size is known to correlate with cell size and division rate, and by extension with numerous organism-level traits such as metabolism, developmental rate or body size. Less well described are the relationships between genome size and other properties of the genome, such as gene content, transposable element content, base pair composition and related features. The rapid expansion of 'complete' genome sequencing projects has, for the first time, made it possible to examine these relationships across a wide range of eukaryotes in order to shed new light on the causes and correlates of genome size diversity. This study presents the results of phylogenetically informed comparisons of genome data for more than 500 species of eukaryotes. Several relationships are described between genome size and other genomic parameters, and some recommendations are presented for how these insights can be extended even more broadly in the future.

Keywords: C-value; genes; genome sequencing; genome size; introns; transposable elements.

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Figures

Figure 1.
Figure 1.
Comparison of genome size estimates based on sequencing or traditional cytogenetic methods. (a) Correspondence between genome sizes estimated from sequence assemblies versus estimates based on Feulgen densitometry or flow cytometry. The two sets of estimates are strongly positively correlated, although there are discrepancies. (b) Relationship between discrepancy according to method of estimation and genome size. The discrepancy becomes larger with increasing genome size, with most of the differences reflecting a lower estimate derived from sequence assembly. (Online version in colour.)
Figure 2.
Figure 2.
Relationships between genome size and (a) gene number, (b) percentage of the genome consisting of protein-coding genes, and (c) proportion of the genome consisting of introns. (Online version in colour.)
Figure 3.
Figure 3.
Relationships between genome size and (a) the proportion of the genome made up of repetitive sequences in general, and (b) transposable elements in particular. (Online version in colour.)
Figure 4.
Figure 4.
Genome size and base pair composition (given as % GC). (Online version in colour.)
See this image and copyright information in PMC

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