Vítek Latzel and colleagues discuss their latest research, published in the Journal of Ecology: Phenotypic diversity generated by a transposable element increases productivity and resistance to competitors in plant populations. Read on to find out more about the role of transposons in biodiversity and resilience:
The last decades of biodiversity-ecosystem functioning experiments have attempted to show that the variety of life around us plays a huge role in keeping our natural world healthy and running smoothly. This variety, also known as biological diversity, is often measured by the number of different species in a community, i.e. species diversity, or by the traits these species possess, i.e. functional diversity. The greater the diversity, the better ecosystems are expected to perform. In other words, more variety of life forms helps ecosystems to be more productive and better deal with stress and environmental variation.
Why does this happen? One theory is that having more species with different traits increases the chances of having a “superstar” species – one that is really good at helping the ecosystem thrive. Another idea is that when different types of species coexist, they are more efficient at using all the limited resources the environment offers.
However, it is not just the differences among species that matter. We and others have shown that the genetic and phenotypic variation within species is also crucial. That means the variety of traits or characteristics within the same plant species, can also impact how well a community and an ecosystem function. These differences can come from random genetic changes within a population or a mixture of different genotypes coexisting together, due to immigration from other populations. Other times, these variations are due to what scientists call “epigenetic” processes, changes that do not tweak the actual DNA sequence but can still influence how an organism’s traits manifest by switching genes on or off, a process that can generate phenotypic variation within a population.
Now, let’s take a fascinating detour. Imagine that tiny bits of “parasitic” DNA, known as “transposable elements” or “jumping genes”, can create phenotypic variability within a species. They can make new copies of themselves that insert in different positions of the genetic code, affecting how certain genes operate and hence altering the organism’s traits. But the million-dollar question is: Do these “jumping genes” cause enough variation in traits to significantly affect how populations and consequently ecosystems function? To answer this question, we designed a study focusing on Arabidopsis thaliana, a widely studied model plant species, and “activated” a specific family of jumping genes to create populations with lower and higher variability between individuals in terms of the transposable element.
🧬 The experiment
With the help of our colleagues Michael and Etienne, we generated lines of A. thaliana, called “TE lines”, by inducing the mobility of the ONSEN transposon via heat stress and certain drugs. In an earlier study, Michael demonstrated that the locations of new ONSEN copies in the DNA of these TE lines are unique, stable, and heritable across generations. Then, we arranged different populations along a gradient of increasing TE line derived diversity: some comprised of a single TE line (monocultures), others of two, four, or sixteen different TE lines (mixtures). We then exposed these plant populations to various conditions: including a standard control environment, a water stress treatment by reduced watering, a competition treatment with other plant species (Plantago lanceolata and Poa annua), and a combination of both treatments.
🔎 Findings
What we found was quite astonishing! The Arabidopsis variants with different ONSEN transposon number and locations in DNA (i.e. TE lines) resulted to be considerably diverse in their phenotypes. Plant features, such as plant size and both above and belowground key functional traits related to the resource-use strategy were significantly altered. But here is where it gets really interesting: we noticed that as more TE lines were included in the population, the more the diversity of important traits increased (i.e. the functional diversity of the population increased) and the more productive the populations got, meaning that they grew more biomass. And there is more: the most diverse plant populations did not just grow more – they also tended to compete better, i.e. they were able to reduce the growth of the competing plants. Thus, besides being more heterogenous in traits, these diverse populations were also more productive and better at resisting competition from other species.
⭐️ Take-home message
So, what is the take-home message? A population composed of individuals in which different transposable elements are “activated”, which is a common situation under natural stressful conditions, can increase functional diversity, and impact ecosystems in a way similar to other forms of biodiversity, e.g. species diversity. In our understanding, this is quite a groundbreaking discovery, as it shows that trait variability within species associated with the function of transposable elements, could also be a key component of biodiversity affecting ecosystems. We hope that our findings will stimulate more research at the intersection of ecology and evolutionary biology concerning the role of transposable elements. There is so much we could learn from studying the ecological and evolutionary role of transposable elements, and we cannot wait to see where this journey takes us next. Stay tuned for more exciting insights from the world of transposable elements!
Vítek Latzel, Czech Academy of Sciences, Czechia.
Read the full article: Phenotypic diversity generated by a transposable element increases productivity and resistance to competitors in plant populations.
