Synthetic genetic circuits reprogram plant root systems

Controlling gene activity is an important step
in improving engineered plants for bioenergy crops.
This research developed synthetic genes that can be combined to achieve specific gene expression patterns
within plants.
The expression of synthetic genes is programmed in the form of Boolean logic gates ("and", "or" and "not") and works in a similar way to a
computer circuit board.
Using synthetic gene circuits, the researchers succeeded in creating predictable, novel patterns
of fluorescent protein expression.
Finally, they used a similar genetic circuit to redesign the root structure
by regulating the number of root branches.

To understand biological function and design new biotechnology applications, scientists need to precisely manipulate gene expression
.
It's the process of converting instructions in DNA into proteins and other products, enabling cells to do their job
in living organisms.
Controlling specific gene expression patterns in plants is challenging
.
One potential solution is to synthesize genetic circuits
.
However, modulating circuit activity in different plant cell types has proven difficult
.
This research developed new genetic circuits that allow precise control of root structures
.
Since the root system is important for absorbing water and nutrients, this approach will allow the design of tailor-made root structures
.
This, in turn, will help researchers design bioenergy crops with improved properties to accommodate the growth
of marginal lands.

In order to build synthetic gene circuits that can predict and regulate gene expression in plants, scientists employ a large number of bacterial gene regulators that are used as synthetic activators or inhibitors of gene expression in plants, also known as transcription factors
.
Using a transient expression system, the researchers demonstrated that synthetic transcription factors and their target DNA sequences (promoters) can direct specific and tunable control
of gene expression.
They designed synthetic promoters that respond to one synthetic transcription factor as simple logic gates that respond to one input, while more complex gates require synthetic promoters
that respond to multiple inputs.
The study found that these logic gates can control expression
in a predictable manner based on specific Boolean rules encoded in engineered genes.

To achieve synthetic gene circuits in a multicellular environment, the researchers used Arabidopsis root as a model system in which endogenous promoters drive tissue-specific expression
of synthetic transcription factors.
Gene circuits generate new expression patterns, which are the result of
successful logical operations.
The researchers further utilized one of the logic gates to quantitatively control the expression of a hormone signaling regulator to regulate the number of root branches in the plant root system of Arabidopsis
.
These results suggest that genetic circuits can now be used to program gene expression across plant cell types, providing a roadmap
for engineering more resilient bioenergy crops.

Synthetic genetic circuits as a means of reprogramming plant roots