xFATE · The Fate of Excitation Energy in Photoinhibited Chloroplasts
Horizon 2020 — Marie Skłodowska-Curie Actions
- Duration
- 2018-03-01 → 2020-02-29
- EU contribution
- €165,599
- Participants
- 1
- Scheme
- MSCA-IF-EF-ST
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Results in brief
The Fate of Excitation Energy in Photoinhibited Chloroplasts
It is common, textbook knowledge that plants use light to grow. The process of photosynthesis relies on capturing light by pigment-binding proteins located in the chloroplast. Then, a series of electron transfer reactions follows, allowing photosynthetic organisms to reduce atmospheric carbon in CO2. However, sunlight is also constantly damaging plants’ photosynthetic apparatus. In particular, Photosystem II (PSII), the multimeric light-driven enzyme capable of water oxidation in the first step of photosynthetic electron transfer, very often becomes damaged and requires disassembly and repair. The impairment of PSII due to light is called photoinhibition. During the course of this Marie Skłodowska-Curie fellowship, we investigated first steps of photodamage process to better understand the Janus-faced relationship between plants and light. Comprehension of the initial stages of photoinhibition is crucial because it is one of the main processes that limits the growth of plants in the natural conditions and as such, possesses a large energetic cost for these organisms. In particular, presence of light prompts plants to develop or trigger mechanisms allowing them to dissipate some of the excess absorbed energy, termed non-photochemical quenching (NPQ). We aimed at describing the location of this quenching after photoinhibition was triggered in living organisms, and then providing full characteristics of this process.
Data: CORDIS, © European Union
Project objective
Plants use light energy to reduce carbon from CO2 to produce sugars. But what happens if too much light is absorbed? Part of the energy is thermally dissipated in a process called non-photochemical quenching; nevertheless excessive absorption inevitably leads to Photosystem II (PSII) damage and photoinhibition. This is followed by degradation and replacement of the reaction center core. Interestingly, photoinhibition is accompanied by a decrease in fluorescence yield, indicating an increase of thermal energy dissipation, leading to the proposal that it functions as a photoprotective mechanism. The molecular mechanism behind this energy dissipation is, however, unknown and the aim of this project is to determine the fate of excitons during photoinhibition. We plan to investigate two scenarios of photoinhibition: one in which the PSII centers are damaged and not degraded, and a second in which the PSII centers are damaged and subsequently degraded. We will use a hypothesis-driven approach for the first scenario and investigate whether the altered thermodynamics of the inhibited PSII can explain changes in fluorescence emission yield and kinetics. The second scenario explores the mechanism that dissipates excitation energy in the absence of the PSII core. Both situations will be probed using spectrally- and temporarily-resolved fluorescence and transient absorption spectroscopy combined with biochemical analyses. Finally, we will use single-molecule spectroscopy on isolated PSII to reveal heterogeneity of PSII damage during photoinhibition.Potentially unraveling new mechanisms of protection against excessive energy absorption, crucial in natural environments where photoinhibition occurs regularly, holds promises not only for our fundamental understanding of energy conversion, but also for future applications in algae and crop cultivation.
Original text from CORDIS.
Participants
- STICHTING VU · AmsterdamCoordinatorNetherlands
Links
Data: CORDIS, © European Union