Heterologous expression of tobacco retrotransposon Tto1 - transposition mechanism and potential applications

Retrotransposons are jumping genes. Although they have rarely been found to fulfill a useful function for the organism were they occur, they can be found in all higher organisms. The reason for this ubiquitous occurrence is probably related to the fact that jumping genes can multiply in their host organisms by inserting copies of themselves into the genome of the host. As a rare event, retrotransposons can even find their way into a new host organism. We wanted to find out whether a host organism has some control over the activity of its retrotransposons. The method of investigation was to bring the retrotransposon Tto1, and a set of variant constructs derived from Tto1, into a plant host that contains no other copies of this element. Subsequently, we monitored whether the element was able to insert new copies into the host genome. Barbara McClintock, discoverer of jumping genes, hypothesized that the host organism plays an active role in the multiplication of these elements. The host was supposed to use this activity to its benefit. However, more recent findings suggest that host organisms have protection mechanisms which help to down-regulate the activity of these parasitic elements, and that host organisms cannot directly use the activity of jumping genes for their benefits. We have discovered a host protection mechanism that shall be studied in more detail in the follow-up project. We found that the retrotransposon Tto1 can be prevented from multiplication in some Arabidopsis plant accessions by targeted distruction of the genetic information contained in the element. Another part of the work carried out during the granting period aimed at a better understanding of the steps involved in the multiplication of Tto1. Once it is possible to turn on multiplication of Tto1 at the experimenters will, the element can be used as a tool for generation of plant mutants. Experiments to continue these efforts are contained in the follow-up project.