They grow in the laboratories of plant researchers around the world - now a team in Cologne has carried out an investigation into the Arabidopsis plants on their doorstep. They discovered that the arable cress has an astonishingly small-scale diversity in the city habitat: the study shows that there are different lines of these sophisticated plants in Cologne that have apparently adapted specifically to the different niches of the urban environment .
Most of us probably walk past them every day - but very few people have probably noticed the most studied plants in the world. Because the thale cress (Arabidopsis thaliana) is tiny and inconspicuous. But in science it is a constant: most of the findings in modern plant research were gained from Arabidopsis. This is because it is particularly suitable for laboratory studies: the small plants can be grown on a mass scale, are robust and easily accessible to molecular biological processes. In order to make results comparable, scientists around the world are working with the descendants of a single individual - a line called Col-0.
Questioning look at Cologne's city growth
The arable cress occurs naturally in almost all of Europe as well as large parts of Asia and Africa. It is already known that there are many different lineages that are adapted to the different environmental conditions of this diverse distribution area. But what about the different living conditions within a smaller area? The team led by senior author Juliette de Meaux from the Institute for Plant Research at the University of Cologne investigated this question. The plants examined in the study were collected by first author Gregor Schmitz on the way to work. He noticed that Arabidopsis in Cologne grows in places with very different environmental conditions. These included places with a low water and nutrient supply, such as small cracks in the pavement, but also habitats with heavy interference, such as frequently mown meadows on busy roads.
In total, the researchers came up with eight location categories. They obtained genetic material from the plants they collected there, which they then sequenced and were thus able to compare. Initially, a surprising diversity was revealed at the genetic level: The plants from the eight locations represent lines that differ genetically to a similar extent as Arabidopsis plants from distant regions of their large distribution area. As subsequent investigations into the properties of the lines showed, the genetic differences are apparently associated with certain characteristics that in turn match the respective location. The Arabidopsis populations in Cologne therefore show large differences in terms of their life cycle characteristics, which had previously only been described for lineages between more distant regions.
Small-scale adjusted lines
This was particularly evident, among other things, in the regulation of the timing of flowering and germination. “The different lines can have very different life cycles,” says de Meaux. “Some are very fast, do not require dormancy or cold before flowering, others are slower, have a high capacity for dormancy and cold is a prerequisite for flowering. “Such diversity in such a small area was surprising.” It became apparent that the characteristics give the plants advantages in the typical locations of the lines, the researchers explain. “In other words: the genetic diversity that we find in the city is not randomly distributed, but corresponds to the specific differences in the urban environment,” says Schmitz.
The study thus documents an evolutionary process at a small level: Because unsuitable lines are filtered out and only those with characteristics suitable for the respective environmental conditions survive, the urban structure developed within the species. This allows Arabidopsis to adapt to local environmental conditions such as temperature and human disturbance specifically adapt to the city. The scientists now want to investigate this interesting aspect of the most studied plant in the world further: They plan to investigate in more detail how environmental heterogeneity shapes certain genetic variants of urban plants.
Source: University of Cologne, specialist article: Journal of Ecology, doi: 10.1111/1365-2745.14211