From instruments through algorithms, new technology is empowering the scientific community to not only discover novel concepts but also to reshape existing ones. A new study from the Sainsbury Laboratory at the University of Cambridge (SLCU) as well as the Department of Plant Sciences has redefined the function and potential of transposable elements (TEs)—also known as transposons—in ways that could have a major impact on everything from economics and alleviating our global food shortage, through health and medicine.
Transposable elements are mobile pieces of DNA that can copy and insert themselves into different parts of the genome. This can result in highly variable outcomes depending on their context: they can amplify genes, silence them, disrupt them, or can simply have no effect at all. Transposons are usually epigenetically silenced to prevent any damage to the genome.
When Barbara McClintock first discovered TEs in corn in the 1940s, transposons were dismissed as junk. That perception has changed as further study has taken place, with this University of Cambridge study bringing unprecedented promise for the potential function of transposons.
Dr. Matthias Benoit and his colleagues looked at the Rider family of transposons in tomato plants, which until now were known to contribute to some physical characteristics of tomato plants like color and tomato shape. But researchers focused in on these transposons, identifying seventy-one Rider elements and leveraging bioinformatics to characterize them in-depth in terms of both genetics and epigenetics. Insertion time was one key metric used.
The results shed some light on contributing factors to how Rider is expressed. Environmental stress was a driver of Rider transcription, particularly dehydration stress regulated by abscisic acid (ABA) signaling, with siRNA production and DNA methylation as the key ways in which Rider activity is controlled.
When a comparison across 110 plant genomes of various species—both tomato and other major crops—was performed to examine the scale of the trends noted, this regulation and expression of Rider was consistent. All findings are consistent with the idea that Rider is mediated by stress—particularly drought—and is present in many different plant species, where it likely contributed to the variation in physical characteristics that have emerged over time.
Long or recurrent drought periods, in particular, could produce these emergent changes via transposons. But with an understanding of environmental contributing factors, scientists open the door for potentially manipulating TEs to produce proactively needed characteristics.
“Identifying that Rider activity is triggered by drought suggests that it can create new gene regulatory networks that would help a plant respond to drought,” Benoit noted. “This means we could harness Rider to breed crops that are better adapted to drought stress by providing drought responsiveness to genes already present in crops. This is particularly significant in times of global warming, where there is an urgent need to breed more resilient crops.”
One of the most promising aspects of this discovery is that transposons already exist in plants, allowing scientists to manipulate existing genomic data rather than introducing new, foreign code that could potentially have other consequences.
Leveraging this technology is possible without breaking conventions on genetic modification, such as the European Union’s code on Genetically Modified Organisms. Mechanisms that are already compliant with safety regulations bode well for their ability to be safely applied to solve major global issues, like the pending food shortage due to overpopulation as well as agricultural challenges that stem from climate change.
Source: Benoit, M. et al. (2019). Environmental and epigenetic regulation of Rider retrotransposons in tomato. PLOS Genetics 15(9)
Reference: University of Cambridge Harnessing tomato jumping genes could help speed-breed drought-resistant crops Univ. of Cambridge: Research News 16 Sep 2019. Web.
