Automated chloroplast screening platform speeds up crop trait development

Chloroplasts, the “lighthouses” of plant cells, are increasingly the subject of synthetic biology. These organelles house the photosynthetic apparatus and host several metabolic pathways of great interest for the engineering of new traits. The insertion of genes into chloroplasts is precise and carries a lower risk of transgene escape.

Despite this potential, chloroplast biotechnology remains in its infancy as it lacks standardized and scalable methods to rapidly test various genetic parts. A research team from the Max Planck Institute for Terrestrial Microbiology in Marburg has presented a microalgae platform that enables automatic, rapid and large-scale testing of genetic changes in chloroplasts.

The study is published in the journal Natural plants.

Automated high throughput at the chloroplast level

In microbiology, optimization through repeated and rapid cycles is common practice. This platform opens plant chloroplasts to high-throughput applications for the first time. The researchers used the microalgae Chlamydomonas reinhardtii. René Inckemann, who led the work in Tobias Erb’s group, explains: “We succeeded in characterizing more than 140 gene-regulatory DNA parts in the alga, covering a wide range of expression strengths. This is essential for fine-tuning genetic circuits. »

All components are compatible with common biotechnology standards, so the DNA library can be easily used in other laboratories. For example, plant scientist Felix Willmund from the nearby Center for Synthetic Microbiology has validated the technology and is already using it to grow robust chloroplasts. Researchers established a workflow capable of generating and analyzing thousands of lines of transplastomic algae – organisms with altered chloroplast genomes – in parallel.

Therefore, multiple genes can now be stably combined in chloroplasts and their activities can be balanced in a predictable manner. This is a crucial step in identifying changes with real potential. By transferring only the most promising variants into more complex plant models, the development process from concept to field testing is accelerated and resources are conserved.

From chloroplasts to cultivated plants

As a proof of concept, the team introduced a synthetic metabolic pathway into the alga’s chloroplasts. The engineered pathway allowed the algae to absorb CO₂ more efficiently under stressful conditions, resulting in a nearly doubling of biomass production: a “turbo-algae”. This demonstrates how targeted interventions on chloroplast metabolism can boost productivity.

The new library provides a solid foundation for a wide range of research, such as improving plant resilience to heat, drought or excessive light, improving nutritional profiles or increasing yield. It can also serve as a platform for new carbon fixation pathways or for the production of high-value natural compounds (e.g. pharmaceutical precursors).

“The platform we present here will play a central role in the Robust Chloroplast research consortium, as well as in the Microbes-4-Climate cluster of excellence, where, together with the University of Marburg, we aim to develop new biological solutions to climate change,” says Erb. “Key technologies like this are essential for targeted research at a pace that matches the urgency of the climate challenge.”