For efficient photosynthesis, plants need lighting conditions that are as uniform as possible and with moderate intensity. On the other hand, if the lighting fluctuates significantly, they become stressed. Experiments on cyanobacteria now show how photosynthetic organisms genetically adapt to the challenges when necessary. The results could also help optimize photosynthesis in crops.
During photosynthesis, plants use light to convert water and carbon dioxide into sugar and oxygen. However, they can only use a limited portion of the light spectrum. “Photosynthesis works most efficiently at low light intensity, while it is throttled down at high light intensity. If the lighting conditions change too frequently, the control mechanisms cannot react quickly enough, which reduces efficiency and thus reduces the yield,” explains Dario Leister from the Ludwig Maximilian University of Munich.
Accelerated evolution in cyanobacteria
Due to the change in clouds, shadows and bright sunlight, outdoor crops are exposed to unsteady lighting conditions to which they have to adapt. One approach to increasing productivity could be to make this adjustment easier for them. Together with a team led by first author Theo Figueroa-Gonzalez, Leister therefore investigated which genetic tricks can mitigate light stress. They used cyanobacteria of the genus Synechocystis as a model organism, which can be used to simulate accelerated evolution thanks to their short generation time.
For their experiment, the researchers put the cyanobacteria under stress by rapidly fluctuating light intensities. “Such conditions, in which high and low light intensities alternate at intervals of one to several minutes, disrupt photosynthesis and damage the photosystems,” explains Leister. In response to these unfavorable conditions, numerous natural mutations occurred in Synechocystis cells, affecting the activity and abundance of several biomolecules important for photosynthesis. These included the protein-pigment complexes photosystem I and II as well as the light-collecting antenna complexes.
Natural mutations
These genetic adaptations made the cyanobacteria more robust to extreme changes in light conditions, allowing them to survive even in conditions that were lethal to the parent strain. In addition, the efficiency of photosynthesis improved in strong light. Similar mutations could possibly also make crops better able to withstand light stress and enable them to use a broader spectrum of light wavelengths. “Our improved Synechocystis lines contain point mutations that can also be transferred to related species using gene editing,” says Leister. “Due to new EU legal initiatives, such changes will probably no longer be considered transgenic in the future. This approach is also more in line with natural processes.”
However, since cyanobacteria are not closely related to land plants, direct transmission is not yet possible. “The next step is to extend the approach from our current study to eukaryotic algae, as these are much more closely related to cultivated plants,” explains Leister. In this way, the researchers want to move step by step closer to their goal of optimizing the photosynthesis system of crops.
Source: Theo Figueroa-Gonzalez (Ludwig-Maximilians-University Munich) et al., Nature Communications, doi: 10.1038/s41467-026-72689-x