Academia Sinica researchers engineer synthetic carbon fixation cycle to boost photosynthesis efficiency in plants

Photosynthesis accounts for the vast majority of carbon sequestration on Earth, yet its inherent inefficiency limits the ability of plants to capture and store additional atmospheric carbon—particularly in the context of rising anthropogenic emissions. Improving the efficiency of carbon fixation has therefore become a key objective in efforts to address climate change, enhance food security, and develop sustainable bioenergy sources.

A multidisciplinary research team at Taiwan’s Academia Sinica, led by President Dr. James C. Liao, has made a significant advance in this field by engineering an artificial carbon fixation cycle through synthetic biology. The newly designed pathway offers a promising strategy to improve photosynthetic performance and accelerate plant growth and lipid biosynthesis—reshaping how plants can be optimized for carbon capture and bioresource production.

The team successfully developed a class of engineered plants—termed “C2 plants”—that incorporate a synthetic carbon fixation mechanism not found in nature. This system enables the direct synthesis of acetyl-CoA, a central metabolic intermediate, from recycled photorespiratory by-products. As a result, the engineered plants achieved a 50% increase in carbon fixation efficiency, along with significantly enhanced biomass accumulation and lipid content.

The findings, published in Science in September 2025, represent a major milestone in synthetic biology and plant metabolic engineering. The work builds upon Dr. Liao’s earlier breakthrough in developing the non-oxidative glycolysis (NOG) pathway in 2013, further advancing the frontier of carbon metabolism redesign.

Artificial Redesign of Photosynthesis in Plants—Surpassing Natural Carbon Fixation

Dr. James C. Liao emphasized that the amount of carbon absorbed by plants through photosynthesis is estimated to be 10 to 20 times greater than total anthropogenic carbon emissions. Despite this, photosynthesis remains inefficient: carbon dioxide is released through photorespiration, and additional CO₂ is emitted during lipid biosynthesis. These two processes represent major limitations to natural carbon fixation. Dr. Liao noted that his motivation to overcome these long-standing bottlenecks began more than a decade ago.

To address these inefficiencies, Dr. Liao’s team developed a synthetic carbon fixation pathway known as the McG cycle (Malyl-CoA glycerate cycle). This engineered pathway is designed to reduce carbon losses from photorespiration and lipid biosynthesis—two key contributors to inefficiency in plant metabolism.

After demonstrating proof-of-concept functionality in E. coli and cyanobacteria, the researchers successfully introduced the McG cycle into Arabidopsis. Remarkably, the synthetic pathway functioned in coordination with the plant’s native Calvin–Benson–Bassham (CBB) cycle, giving rise to a dual-cycle carbon fixation system.

Breakthrough in Synthetic Biology Boosts Plant Biomass and Lipid Yield via Enhanced Carbon Fixation

In nature, plants have evolved specialized photosynthetic strategies to minimize carbon loss caused by photorespiration. Among them, C4 plants such as maize and sugarcane utilize a spatial separation mechanism to concentrate carbon dioxide, while CAM (Crassulacean Acid Metabolism) plants—including cacti, pineapples, orchids, and dragon fruit—employ temporal separation to limit CO₂ loss.

The team at Academia Sinica has now developed a third, synthetic strategy: the conversion of C3 plants into engineered “C2 plants” using a rationally designed metabolic pathway known as the McG cycle. These modified plants demonstrated a substantial increase in carbon fixation efficiency, along with accelerated growth and a two- to three-fold increase in total biomass. They also exhibited significantly elevated lipid accumulation, making them promising candidates for sustainable aviation biofuel production.

“This is a fundamental breakthrough in basic science,” said Dr. James C. Liao, President of Academia Sinica and lead author of the study. “While it will not immediately resolve global challenges such as carbon emissions or food insecurity, it shows that synthetic biology can open up entirely new trajectories for reprogramming plant metabolism.”

Despite the promising results, the team acknowledges that several hurdles remain before this strategy can be applied at scale. These include improving the genetic stability of the introduced pathway, transitioning from transgenic approaches to precision gene-editing technologies, and validating the system’s effectiveness in economically important crop species such as rice and tomatoes.

This work represents a critical step forward in the rational engineering of plant metabolic systems, offering a new blueprint for enhancing biological carbon capture and supporting the development of next-generation bioenergy platforms.

Co-author Dr. Shu-Hsing Wu, Distinguished Research Fellow at Academia Sinica’s Institute of Plant and Microbial Biology (IPMB), emphasized that the study underscores the transformative potential of synthetic biology in plant science. “By rationally reprogramming metabolic pathways, we can unlock growth and productivity in ways that natural evolution has yet to explore,” she said.

Dr. Kuo-Chen Yeh, Director of the Agricultural Biotechnology Research Center (ABRC), highlighted Academia Sinica’s strategic support for advancing synthetic biology research. “We’ve established an interdisciplinary team of plant metabolic engineers, synthetic biologists, and translational scientists,” he noted. “Our next step is to evaluate this dual-cycle carbon fixation system in key agricultural crops such as rice and tomatoes.”

The study’s first author, Dr. Kuan-Jen Lu, now an Assistant Research Fellow at ABRC, joined the project during her postdoctoral training in Dr. Liao’s laboratory. “I spent countless hours designing and performing experimental workflows and cultivating plants in the lab,” she recalled. “When we observed the McG plants growing to nearly three times the size of wild-type controls, we were astonished. Both Dr. Liao and Dr. Yeh exclaimed, ‘Wow!’—and in that moment, all the years of effort felt worthwhile.”

Following these initial breakthroughs, the team spent two additional years conducting validation experiments, optimizing the system, and navigating the peer-review process. “This extended research phase allowed us to gain deeper insights into the physiological effects of the synthetic carbon fixation cycle,” said Lu. “Thanks to the collaborative support of Academia Sinica’s core facility researchers, the work was successfully brought to publication.”

Funding and Acknowledgments

This research was conducted in collaboration with Dr. Chia-Wei Hsu of Academia Sinica’s Metabolomics Core Facility, Dr. Wann-Neng Jane, Research Specialist at the Electron Microscopy Facility, Dr. Kuo-Chen Yeh of the Agricultural Biotechnology Research Center (ABRC), and Dr. Shu-Hsing Wu of the Institute of Plant and Microbial Biology (IPMB). The project was supported by Academia Sinica’s Alpha Team Project and the Innovative Translational Agricultural Research Program.

The full article, “Dual-cycle CO₂ fixation enhances growth and lipid synthesis in Arabidopsis thaliana”, was published in Science in September 2025 and is available at: https://www.science.org/doi/10.1126/science.adp3528