Transposable elements are present in almost all genomes including that of humans. These mobile DNA sequences are capable of invading genomes and their impact on genome evolution is substantial as they contribute to the genetic diversity of organisms. The mobility of transposable elements can cause deleterious mutations, gene disruption and chromosome rearrangements that may lead to several path...

Y OUNG et al. (1994) recently found that a putative transposable element (Lytl) is present at high abundance in the genomes of individuals sampled from a group of red-fruited species of Lycopersicon, and at a much lower abundance in green-fruited species of this genus. Similar or somewhat lower abundances were found in Solanum species believed to be closely related to Lycopersicon, and even low...

Transposable elements (TEs) are powerful facilitators of genome evolution, and hence of phenotypic diversity as they can cause genetic changes of great magnitude and variety. TEs are ubiquitous and extremely ancient, and although harmful to some individuals, they can be very beneficial to lineages. TEs can build, sculpt, and reformat genomes by both active and passive means. Lineages with activ...

We have characterized the two families of SINE retroposons present in Arabidopsis thaliana. The origin, distribution, organization, and evolutionary history of RAthE1 and RAthE2 elements were studied and compared to the well-characterized SINE S1 element from Brassica. Our studies show that RAthE1, RAthE2, and S1 retroposons were generated independently from three different tRNAs. The RAthE1 an...

Microsporidian genomes are the leading models to understand the streamlining in response to a pathogenic lifestyle; they are gene-poor and often possess small genomes. In this study, we show a feature of microsporidian genomes that contrasts this pattern of genome reduction. Specifically, genome investigations targeted at Anncaliia algerae, a human pathogen with a genome size of 23 Mb, revealed...

Transposable elements are often considered parasitic DNA sequences, able to invade the genome of their host thanks to their self-replicating ability. This colonization process has been extensively studied, both theoretically and experimentally, but their long-term coevolution with the genomes is still poorly understood. In this work, we aim to challenge previous population genetics models by co...

The nature of the role played by mobile elements in host genome evolution is reassessed considering numerous recent developments in many areas of biology. It is argued that easy popular appellations such as ‘‘selfish DNA’’ and ‘‘junk DNA’’ may be either inaccurate or misleading and that a more enlightened view of the transposable element-host relationship encompasses a continuum from extreme pa...

The apparent morphological stasis in the lineage of the coelacanth, which has been called a "living fossil" by many, has been suggested to be causally related to a slow evolution of its genome, with strongly reduced activity of transposable elements (TEs). Analysis of the African coelacanth showed that at least 25% of its genome is constituted of transposable elements including retrotransposons...

vii CHAPTER I. GENERAL INTRODUCTION 1 Transposable elements 1 Integrase and integration 3 Ty elements and targeted integration 6 Heterochromatin and silencing 9

The relationship between genome size and the percentage of transposons in 161 animal species evidenced that variations in genome size are linked to the amplification or the contraction of transposable elements. The activity of transposable elements could represent a response to environmental stressors. Indeed, although with different trends in protostomes and deuterostomes, comprehensive change...