Helitrons: genomic parasites that generate developmental novelties.

Helitrons are notoriously difficult to identify, due to low conservation of their internal sequences and few characteristic sequence features. New sequencing technologies and genome analysis tools open advanced possibilities for the identification of Helitrons, allowing one to monitor Helitron activity and its consequences. Helitrons can transpose gene fragments, including regulatory elements of genes, thereby creating new circuits of gene regulation. In plants, this has been demonstrated for endosperm-specific regulatory elements and elements regulating the response to herbivores, but more examples are likely to be discovered. Helitron-captured gene fragments can elicit evolutionary conflicts. This is because the host silencing machinery will target the Helitron and the captured gene, causing transacting silencing effects on the donor gene. Helitrons, classified as DNA transposons, employ rolling-circle intermediates for transposition. Distinguishing themselves from other DNA transposons, they leave the original template element unaltered during transposition, which has led to their characterization as 'peel-and-paste elements'. Helitrons possess the ability to capture and mobilize host genome fragments, with enormous consequences for host genomes. This review discusses the current understanding of Helitrons, exploring their origins, transposition mechanism, and the extensive repercussions of their activity on genome structure and function. We also explore the evolutionary conflicts stemming from Helitron-transposed gene fragments and elucidate their domestication for regulating responses to environmental challenges. Looking ahead, further research in this evolving field promises to bring interesting discoveries on the role of Helitrons in shaping genomic landscapes. [ABSTRACT FROM AUTHOR]

Copyright of Trends in Genetics is the property of Elsevier B.V. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)