PhD student Pierrick Bru is measuring how much light energy is converted into heat in Arabidopsis thaliana plants. Photo: Alexis Brun
Just like people can get sunburned, plants can also suffer from too much sunlight. To stay healthy, they use an internal “sun protection mechanism”. Pierrick Bru, a PhD student working with Alizée Malnoë at Umeå Plant Science Centre and Umeå University, has been studying a special component of this plant "sun protection mechanism" called qH and found it is quite adaptable.
The magic of photosynthetic organisms is that they can produce energy from sunlight. Plants have tiny structures in their cells, that, similarly to mini solar panels, catch sunlight and turn it into energy-rich compounds which the plant is then utilizing to grow and stay healthy. However, when there is too much light, these structures can get overloaded and damaged. To prevent this from occuring, plants use a photoprotection mechanism known as non-photochemical quenching, which converts excess sunlight into heat, allowing it to dissipate harmlessly.
“qH is one of the components of this non-photochemical quenching system and it is the component that we focussed on in our research,” explains Pierrick Bru. “This component does not work quickly. It takes hours to turn on and off, and it is mainly active when plants are under prolonged excess of light stress, especially when combined with other environmental cues such as cold and/or drought.”
To understand more about qH, Pierrick and his colleagues did experiments with the plant model organism Arabidopsis thaliana. They modified the plant by removing one or more of the mini solar panels and found that the plant has a backup system: if one panel is missing, the others can compensate for it. However, when a particular small panel, known as Lhcb6, is not there, qH could not work properly and less of the excess sunlight was turned into heat.
The researchers did not stop here but went on to investigate further how this photoprotection mechanism works and to search for other missing actors that regulate the qH mechanism. They introduced random changes in the genome of Arabidopsis thaliana, where the plant’s blueprint is stored, and looked for modified plants that had issues with their sunlight protection. Out of 22,000 plants screened, they found 150 with altered protection mechanisms. They took a closer look at 61 of them and identified about eighteen new actors that could be involved in the qH mechanism.
Two of these actors are involved in building or repairing photosystem II – one of the two functional units where photosynthesis takes place. If either of the two actors found did not work well, photosystem II could not function as usual, and this caused problems also for the plants to use the qH sun protection mechanism.
Pierrick Bru and his colleagues do not know yet how exactly the defects of photosystem II impact the qH protection mechanism. They will continue investigating this in the model organism Arabidopsis thaliana, where it is easy and fast to make new discoveries. This understanding will open doors to investigate if photoprotection qH is regulated similarly in crops.
“Crops are suffering already now from more extreme weather conditions caused by climate change. This will affect our capacity to grow healthy crops and good food for an increasing population,” explains Pierrick Bru. “Understanding how qH works and how plants cope with environmental stress will help to find ways to improve plant resistance to excess of sunlight, improving plant growth and increase agriculture productivity.”
About the public defence
Pierrick Bru, Umeå Plant Science Centre, Department of Plant Physiology, Umeå University, defends his PhD thesis with the title “Investigating the molecular mechanism of photoprotection qH, in Arabidopis thaliana” on Friday, 8th of December 2023. Faculty opponent is Stefano Caffarri, Department of Biology, Aix-Marseille University, Marseille, France. The thesis was supervised by Alizée Malnoë.
Link to Pierrick Bru's PhD thesis
For more information, please contact:
Pierrick Bru
Umeå Plant Science Centre
Department of Plant Physiology
Umeå University
Email:
Text: Pierrick Bru, Anne Honsel