Helitron in wheat

Transposons play a pivotal role in genome evolution and phenotypic variation in numerous eukaryotic species reaching from plants to animals1. Helitrons, a recently identified category of transposons, remain poorly understood in terms of epigenetic regulation and real-time mobilization2. Here, we introduce a Helitron family named Xuan-Feng (Chinese 'whirlwind'), which can be mobilized in wheat. Under epigenetic impairment, heat stress induces the formation of extrachromosomal circular DNA (eccDNA) and de novo insertions of the non-autonomous Xuan element. Combining whole-genome sequencing with genetics allowed the identification of the functional autonomous Feng element in the wheat genome that is required for Xuan mobilization. Notably, this Feng element is stress-responsive and encodes an intact Helitron transposase which catalyzes eccDNA formation and integration. Our evolutionary analysis across 17 Triticeae (wheat and wheat relatives) genomes revealed a constant copy number of autonomous Feng members, supporting the notion of an active maintenance of a steady state of TE insertions3. These findings represent a step forward in studying active Helitrons in virtually any organism which will contribute to a better understanding of their role in genome evolution.