Nature Genetics
20, 43 - 45 (1998)
doi:10.1038/1695
The paleontology of intergene retrotransposons of maizePhillip SanMiguel1, 2, Brandon S. Gaut3, Alexander Tikhonov1, Yuko Nakajima1
& Jeffrey L. Bennetzen1, 21
Department of Biological Sciences, Purdue University
, West Lafayette, Indiana 47907-1392,
USA. 2
Genetics Program, Purdue University, West
Lafayette, Indiana 47907-1392, USA. 3
Department of Ecology and Evolutionary Biology, University
of California, Irvine, California 92697-2525
, USA.
Correspondence should be addressed to Jeffrey L. Bennetzen maize@bilbo.bio.purdue.eduRetrotransposons, transposable elements related to animal retroviruses,
are found in all eukaryotes investigated and make up the majority of many
plant genomes1,
2,
3,
4,
5. Their ubiquity points to their importance,
especially in their contribution to the large-scale structure of complex genomes.
The nature and frequency of retro-element appearance, activation and amplification
are poorly understood in all higher eukaryotes. Here we employ a novel approach
to determine the insertion dates for 17 of 23 retrotransposons found near
the maize adh1 gene, and two others from unlinked sites in the maize
genome, by comparison of long terminal repeat (LTR) divergences with the sequence
divergence between adh1 in maize and sorghum. All retrotransposons
examined have inserted within the last six million years, most in the last
three million years. The structure of the adh1 region appears to be
standard relative to the other gene-containing regions of the maize genome,
thus suggesting that retrotransposon insertions have increased the size of
the maize genome from approximately 1200 Mb to 2400 Mb in the last three million
years. Furthermore, the results indicate an increased mutation rate in retrotransposons
compared with genes.
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