Nature Genetics
37, 997 - 1002 (2005)
Published online: 31 July 2005; | doi:10.1038/ng1615
Gene duplication and exon shuffling by helitron-like transposons generate intraspecies diversity in maizeMichele Morgante1, Stephan Brunner2, Giorgio Pea2, 3, Kevin Fengler2, Andrea Zuccolo1, 3
& Antoni Rafalski21
Dipartimento di Scienze Agrarie ed Ambientali, Universita' di Udine, Via delle Scienze 208, 33100
Udine, Italy. 2
DuPont Crop Genetics Research, DuPont Experimental Station Building E353, Wilmington, Delaware
19880-353, USA. 3
Present addresses: Università degli Studi di Milano, Dipartimento di Scienze Biomolecolari e Biotecnologie, Via Celoria 26, 20133
Milano, Italy (G.P.); Arizona Genomics Institute, University of Arizona, Tucson, Arizona
85721, USA (A.Z.).
Correspondence should be addressed to Michele Morgante michele.morgante@uniud.it We report a whole-genome comparison of gene content in allelic BAC contigs from two maize inbred lines. Genic content polymorphisms involve as many as 10,000 sequences and are mainly generated by DNA insertions. The termini of eight of the nine genic insertions that we analyzed shared the structural hallmarks of helitron rolling-circle transposons1,
2,
3. DNA segments defined by helitron termini contained multiple gene-derived fragments and had a structure typical of nonautonomous helitron-like transposons. Closely related insertions were found in multiple genomic locations. Some of these produced transcripts containing segments of different genes, supporting the idea that these transposition events have a role in exon shuffling and the evolution of new proteins. We identified putative autonomous helitron elements and found evidence for their transcription. Helitrons in maize seem to continually produce new nonautonomous elements responsible for the duplicative insertion of gene segments into new locations and for the unprecedented genic diversity. The maize genome is in constant flux, as transposable elements continue to change both the genic and nongenic fractions of the genome, profoundly affecting genetic diversity.
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