Stress-induced mobilization of retrotransposons for plant breeding

Environmental stresses can trigger the activation and amplification of retrotransposons (retroTEs) in eukaryotes. The mobilization of retroTEs via their characteristic copy and paste mechanism, known to induce (epi)genetic diversity, is one the major drivers of genome evolution in plants and possibly most eukaryotes. Due to their potential as powerful mediators of adaptation to different environmental conditions, retroTEs are increasingly gaining attention as an endogenous genetic resource that could be harnessed for plant breeding. However, as transposition can also lead to detrimental mutations, retroTE mobility is normally limited by sophisticated silencing pathways implemented by their hosts.
In this work, I uncover the role of RNA polymerase II (Pol II) as a key regulator of retroTE-activity. By using two different inhibitors that specifically target the initiation of TE-silencing in plants, I was able to mobilize a stress responsive retroTE in Arabidopsis and thus opened up the so far sealed (epi)genetic resource of retroTEs for plant breeding. Due to the observation that the treatment with the two inhibitors also mobilized a retroTE in the distantly related rice crop, I conclude that this approach could in principle be used to mobilize retroTEs in virtually any plant. Besides major advances in the field of epigenetics and retroTE- silencing, this work indeed provides the basis for a completely new approach that has also been patented and already commercialized in a start-up company. Thus, the second part of this thesis is thematically situated at the interface of science & innovation and science & policy. The described measures taken to communicate and discuss this new breeding approach form the basis for the futures public debate on the topic.