The effects of rapid climate change pose challenges for many crops. A new method of genetic engineering could possibly provide a remedy: With so-called synthetic genetic circuits, researchers can specifically influence certain genes in individual areas of the plant. Using a model plant as an example, a research team has now succeeded in controlling root growth without affecting the rest of the plant. The method could help develop crops that can absorb water and nutrients from the soil more effectively.
Although it is possible to introduce specific genes into the genome of an organism in a targeted manner using genetic engineering methods that have been used up to now, these genes typically develop their effect non-specifically in all cells of the organism. Classic plant breeding is even less precise: Here breeders have to hope for random favorable gene mutations, which they make more likely with the help of chemicals or radioactive radiation, but cannot specifically influence. In view of the rapid environmental changes caused by man-made climate change, an important research goal is to change crops as precisely as possible in order to make them fit for the new conditions.
Programming code for plants
A team led by Jennifer Brophy from Stanford University in California has now used the example of thale cress (Arabidopsis thaliana) as a model plant to apply a new method that brings this goal closer: The researchers developed so-called synthetic genetic circuits with which they can sequence genes in individual areas of a gene plant can regulate in a targeted manner without affecting the rest of the plant. Similar to a computer code, the gene circuits work with certain switches that switch genes and other signaling pathways on and off depending on the other conditions.
“Our synthetic genetic circuits allow us to engineer very specific root systems or very specific leaf structures,” says Brophy. “This allows us to make plant engineering much more precise.” Her team developed and tested over a thousand potential circuits. 188 of them turned out to be useful. The researchers are now making these available to other groups in a database for synthetic DNA. They thus form a basis for future further developments in this area.
Adaptations to climate change
Brophy and her team demonstrated the possible uses of synthetic genetic circuits in plants on thale cress. They combined several switches to specifically and predictably influence the root growth of the plant. By altering the level of expression of a gene, they were able to alter the density of branching in the root system. “The shape of a plant’s root system influences its ability to reach important nutrients in the soil and absorb water during drought,” the researchers explain. For example, a shallow, well-branched root system is better able to absorb phosphorus, which is mostly found near the surface. A deep root system, on the other hand, is better able to absorb water and nitrogen.
Using the same type of genetic switches that the team used to self-regulate root development, plants could be enabled to react independently to changing soil conditions in the future. For example, it would be conceivable that genes that allow the roots to grow deeper are specifically activated only when there is a drought. In future experiments, the researchers also want to apply their method to crops, for example to enable them to absorb more water and carry out photosynthesis more efficiently. “Many modern crops are no longer able to react to changes in the nutrient content of the soil,” explains Brophy’s colleague José Dinneny.
Milestone in genetic engineering
“Climate change is changing the agricultural conditions under which we grow the crops we depend on for food, fuel, fiber and raw materials for medicines,” said Brophy. “If we’re not able to produce these crops on a large scale, we’re going to face a lot of problems. This work aims to help ensure that we have plant varieties that we can continue to grow even when the environmental conditions in which we grow them become less favorable.”
In a commentary accompanying the study, also published in the journal Science, Simon Alamos and Patrick Shih of the University of California, Berkeley write: “The Brophy et al. The knowledge gained is key to future success in the implementation and realization of combinatorial circuits not only in plants but also in other complex biological systems. This work is a milestone in the genetic engineering of a whole, fully developed multicellular organism and points to the challenges ahead.”
Source: Jennifer Brophy (Stanford University, CA, USA) et al., Science, doi: 10.1126/science.abo4326