Geneticists at Stanford University have discovered a way to carefully control the structure of plant roots as they grow and branch.
By manipulating the depth and shape of a growing root system, researchers hope to one day be able to reprogram crops to make them more resilient to climate change.
A shallower root system, for example, could help crops better absorb phosphorus near the surface. Whereas a deeper root system might be better for collecting water and nitrogen.
“Our synthetic genetic circuits will allow us to build very specific root systems or very specific leaf structures to see what is optimal for the difficult environmental conditions that we know are coming,” explains bioengineer Jennifer Brophy of Stanford University.
“We’re making plant engineering much more precise.”
The genetic techniques used by Brophy and his colleagues to achieve such high precision could reprogram plants much faster than they could otherwise be adapted and more precisely than they can be bred for desirable traits.
Using cells from a tobacco plant, the researchers created a synthetic genetic circuit that controls gene expression and showed how it works in another plant.
You can think of the genetic circuit as a computer code with logic gates. Only correct input values can enter the gate and produce an output.
These biological circuits are also similar to electrical circuits with switches, like the ones that power your phone.
An interpretive “schematic” of the synthetic genetic circuits connecting plant roots. (Jennifer Brophy/Standford University)
In a cell, these gates, which ultimately lead to gene expression, can only be opened by synthetic transcriptional “promoters” that are specific to certain plant tissues. This means researchers can potentially control which cells in a plant express which genes, changing how the plant grows.
By creating a series of synthetic logic gates for a single gene associated with lateral root development, the researchers were able to manipulate the growth of a small weed plant, known as Arabidopsis thaliana.
By changing the expression of this gene, the researchers altered the density of the branches in the plant’s root system without affecting other root properties.
This is a major breakthrough because another study previously showed how small changes in this root development gene can affect all kinds of root properties, such as root hair development or root growth. the primary root.
“To uncouple root branching from other developmental processes, we expressed the slr-1 mutant gene using a tissue-specific promoter found only in lateral root stem cells,” the researchers write .
Next, the authors plan to test their reprogrammed genetic circuits in sorghum, which is a unique crop that holds promise as a biofuel. The team hopes to improve sorghum’s ability to absorb water and perform photosynthesis more efficiently.
If this genetic technique proves effective, its possibilities are limitless. Reprogramming crops using synthetic genetic circuits will, however, require careful fine-tuning.
“We have modern varieties of crops that have lost the ability to respond to where the nutrients are in the soil,” says plant biologist José Dinneny, also of Stanford.
“The same kind of logic gates that control root branching could be used to, for example, create a circuit that takes into account both nitrogen and phosphorus concentrations in the soil, and then generate an optimal output for these conditions”.
The study was published in Science.