A constant cat-and-mouse game takes place in all eukaryotic cells: transposone, which are also called jumping genes because they can move in the genome, threaten the genome of the cell by causing mutations and re-arrangements in genome. To protect your genome, plants try to shut down transposone by compacting the DNA -containing DNA in such a way that it becomes inaccessible to the cellular machine. For this purpose, plants use various epigenetic markings, such as DNA methylation or modifications to the histone proteins that organize and pack the DNA. These two markings reinforce each other and thereby cause reliable and stable shutdown of the transposone.
Over time, these decommissioned transposones degenerate and crush into fragments. These “old” or degenerated transposone are no longer able to jump and therefore can no longer cause any damage in the genome. Your accumulation and repetitive nature can continue to cause genomic new arrangements and re-arrangements. In order to prevent this, degenerated transposone are also kept under control by DNA methylation and histone modification: with the same mechanisms that caused their original decommissioning.
Researchers: Inside the group of Arturo Marí-Ortóñez at the Gregor Mendel Institute for Molecular Plant Biology (GMI) of the Austrian Academy of Sciences now found that Spirodela polyrhiza -The oldest member of the water lenses family-“old”, degenerated transposone, surprisingly, does not mark with DNA methylation: Instead, an epigenetic marking that has so far been little examined is used, which in Spirodela, in contrast to other plants, remains independent of the DNA methylation. The new findings of the researchers: inside complement the conventional models of transposon regulation and underline how important it is to examine a variety of different model organisms.
Simple and yet effective
Waterlens – Small aquatic plants that cover the ponds – became increasingly easier and easier in the course of evolution. They no longer multiply through sexual reproduction, but rather through frequent cloning. This evolutionary path has led to the fact that Spirodela polyrhizaThe species examined by Marí-Ortóñez has lost important genes that are involved in development processes.
Although Spirodela has a similarly large genome with a similar transposon content as the model plant Arabidopsis Thaliana, researchers have observed remarkably low methylation values in the genome of Spirodela. Despite this low methylation, Spirodela manages to keep transposone in chess, which shows that flowering plants can also regulate transposone without DNA methylation.
When comparing Spirodela with Arabidopsis, the researchers discovered: Inside that Spirodela lacks some proteins that are used in other plants for DNA methylation. Surprisingly, Marí-Ortóñez and his team were still able to observe that Spirodela uses DNA-methylation and histone modifications for the decommissioning of recently integrated intacts. These are the same markings that are also used by other plants. However, if transposone in Spirodela degenerates, you lose all the decommissioning markings except for one – a so far little examined type of histone modification, which is also connected to the transposon silcing. “For the first time, we have shown that some flowering plants can maintain heterochromatin markings even without DNA methylation,” explains Arturo Marí-Ortóñez. “The unique epigenetic landscape of Spirodela could be related to its reproductive strategy, which is based on a quick clonal increase.”
Tiny plants, enormous potential
The results of the team indicate that Spirodela concentrates to stand still potentially active transposone, which are a clear threat to the integrity of the genome, but non -fragmented transposure. The researchers now want to find out how Spirodela maintains epigenetic markings on degenerated transposons without DNA methylation. “The specific role of this epigenetic marking is still unknown, but could be important to understand how other duties and other plants deal with transposons. So we come a little closer to solving the puzzle of how plants defend their genome, ”says Arturo Marí-Ortóñez.
Apart from their role as a model plant in basic research, water lenses have recently developed into a powerful biotechnological tool: their simple construction and their quick spread make dwarf lenses an ideal production platform for the sustainable production of medicines, biofuels and even food. New insights into the genetic functions of duty also enable the further development of biotechnological strategies. As a result, the great potential of these small aquatic plants for biotechnology could be used even better.