LTR retrotransposons and flowering plant genome size: emergence of the increase/decrease modelVitte C. · Panaud O.
aLaboratoire Ecologie, Systématique et Evolution, Université Paris-Sud, Orsay; bLaboratoire Genome et Developpement des Plantes, Perpignan (France)
Long Terminal Repeat (LTR) retrotransposons are ubiquitous components of plant genomes. Because of their copy-and-paste mode of transposition, these elements tend to increase their copy number while they are active. In addition, it is now well established that the differences in genome size observed in the plant kingdom are accompanied by variations in LTR retrotransposon content, suggesting that LTR retrotransposons might be important players in the evolution of plant genome size, along with polyploidy. The recent availability of large genomic sequences for many crop species has made it possible to examine in detail how LTR retrotransposons actually drive genomic changes in plants. In the present paper, we provide a review of the recent publications that have contributed to the knowledge of plant LTR retrotransposons, as structural components of the genomes, as well as from an evolutionary genomic perspective. These studies have shown that plant genomes undergo genome size increases through bursts of retrotransposition, while there is a counteracting process that tends to eliminate the transposed copies from the genomes. This process involves recombination mechanisms that occur either between the LTRs of the elements, leading to the formation of solo-LTRs, or between direct repeats anywhere in the sequence of the element, leading to internal deletions. All these studies have led to the emergence of a new model for plant genome evolution that takes into account both genome size increases (through retrotransposition) and decreases (through solo-LTR and deletion formation). In the conclusion, we discuss this new model and present the future prospects in the study of plant genome evolution in relation to the activity of transposable elements.
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Supported by the French Ministry of Research and Education.
Manuscript received 10 December 2003;
accepted in revised form for publication by J.-N. Volff 14 April 2004.
Number of Print Pages : 17
Number of Figures : 4, Number of Tables : 2, Number of References : 152
Cytogenetic and Genome Research
Vol. 110, No. 1-4, Year 2005 (Cover Date: 2005)
Journal Editor: H.P. Klinger, Bronx, N.Y.; M. Schmid, Würzburg
ISSN: 1424–8581 (print), 1424–859X (Online)
For additional information: http://www.karger.com/cgr