PgmNr P355: Transposon-induced genome rearrangements in maize: mechanisms and genetic impacts.

Authors:
T. A. Peterson 1 ; J. Zhang 1 ; D. Wang 1 ; T. Zuo 1 ; W. Su 1 ; S. P. Sharma 1 ; D. F. Weber 2


Institutes
1) Iowa State Univ, Ames, IA; 2) Illinois State Univ, Normal, IL.


Abstract:

Barbara McClintock showed that Transposable Elements (TEs) not only move within the genome, but they can also induce major changes in genome structure and gene expression.  How do these changes occur?  We are studying the mechanisms by which DNA transposons duplicate and rearrange sequences, ranging from individual genic components (enhancers and exons), up to segments of 15 Mbp and containing 300 genes or more. The highly active maize Ac/Ds transposon system can undergo Alternative Transposition (AT) reactions that involve the termini of different nearby TE copies:  5’ and 3’ termini in direct orientation can undergo Sister Chromatid Transposition to produce flanking deletions and inverted duplications; while termini in reversed orientation can undergo Reversed-Ends Transposition reactions resulting in inversions, deletions, translocations and duplications (Zhang et al., 2009, 2013). Ac/Ds elements preferentially insert into genic regions, which greatly enhances the frequency of exon shuffling events.  We show that Ac/Ds transposons can, in a single step, create new chimeric genes which are expressed and produce functional products and visible phenotypes. In addition, AT events that occur during DNA replication generate novel Composite Insertions by DNA re-replication (Zhang et al., 2014).  These Composite Insertions can carry enhancers that induce ectopic expression of nearby genes. AT reactions are not unique to Ac/Ds elements, but occur also in other hAT family transposons which are widespread in eukaryotes.  Our results demonstrate that AT events can be an effective mechanism for the generation of new genes, and provide new insight into the impacts of transposable elements on genome evolution. 

For animations of Alternative Transposition, see http://thomasp.public.iastate.edu/transposition.html.