Dual-cycle CO2 fixation enhances growth and lipid synthesis in Arabidopsis thaliana

Kuan-Jen Lu, Chia-Wei Hsu, Wann-Neng Jane, Mien-Hao Peng, Ya-Wen Chou, Pin-Hsuan Huang, Kuo-Chen Yeh, Shu-Hsing Wu, and James C. Liao 

SCIENCE; 11 Sep 2025; Vol 389, Issue 6765; DOI: 10.1126/science.adp3528

Abstract

Carbon fixation through the Calvin-Benson-Bassham (CBB) cycle accounts for the majority of carbon dioxide (CO₂) uptake from the atmosphere. The CBB cycle generates C3 carbohydrates but is inefficient at producing acetyl–coenzyme A (CoA) (C2), which is the universal precursor for synthesizing lipids. In this work, we introduced in Arabidopsis thaliana a new-to-nature CO₂ fixing cycle, malyl-CoA-glycerate (McG) cycle, which together with the CBB cycle forms a dual-cycle CO₂ fixation system. This cycle can fix one additional carbon by phosphoenolpyruvate carboxylase and convert the photorespiration product, glycolate, to acetyl-CoA. Plants with the McG cycle show enhanced protein abundance in their photosystems and enhanced photosystem II efficiency. McG plants had doubled CO₂ fixation rates under atmospheric CO₂, increased lipid production, pronounced growth enhancement, and tripled the seed yield.

See https://www.science.org/doi/10.1126/science.adp3528

Figure 1:

A C2-centric dual-cycle carbon fixation system in Arabidopsis.

The McG (blue) cycle is introduced to Arabidopsis chloroplasts to work with the native CBB cycle (black) for more efficient acetyl-CoA synthesis and bypassing photorespiration. The McG plants grew much larger and produced more seeds and lipids through a positive feedback loop. [The figure was created with BioRender.com.]