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Control of Light Use Efficiency in Plants and Algae - From Light to Harvest

Final Report Summary - HARVEST (Control of Light Use Efficiency in Plants and Algae - From Light to Harvest)

The Marie Curie Initial Training Network ‘HARVEST’ brought together major high-quality EU centres and private companies from nine European countries with expertise in the light reactions of photosynthesis in plants and algae and with great interest in interdisciplinary collaborative research. The network provided between October 2009 and October 2013 a training opportunity for young researchers in molecular biosciences and biophysical sciences in the context of practical applications in instrument development, agronomy and biotechnology.

The full title of HARVEST is ‘Control of light use efficiency in plants and algae – from light to harvest’. The co-workers in HARVEST realized that a successful operation of photosynthesis in plants and algae requires the integration of photophysical and photochemical processes occurring on the (sub-)picosecond timescale with biosynthetic and developmental processes that take place over seconds, days and months. This has evolved a hierarchy of structural and functional organisation in photosynthetic organisms: chromophores bound to proteins, arranged in macro-molecular complexes, organised as supramolecular membrane domains, associated together in grana membrane superstructures, found in specialised organelles, cells and organs and grown in natural conditions or optimized conditions in greenhouses of photobioreactors. Moreover, the supply of the primary driving force (light) is variable in terms of its intensity and spectral quality, environmental factors are usually subject to continuous change, and the demand for competence varies during the growth and development of the organism. To cope with these variations, and at the same time to ensure efficiency, stability and survival, most of the photosynthetic process is under the control of multilevel regulatory mechanisms. At the very centre of the environmental adaptation of plants and photosynthetic micro-organisms is the optimisation between efficient collection of light energy and the prevention of its damaging photo-oxidising effects. Such photoregulation decreases the photosynthetic efficiency very substantially, so understanding these mechanisms and taking appropriate measures can have important socio-economic implications for, e.g. agriculture, food security and biofuels or other products.

HARVEST made significant progress on the following scientific topics:
1. Photoregulation by non-photochemical quenching in the green plants
2. Photoregulation by state transitions in the green plants
3. Photoregulation in C4 and C3/CAM plants
4. Photoregulation in evergreens and mosses
5. Photoregulation in green algae and diatoms
6. Photoregulation in cyanobacteria
7. Photophysical properties of carotenoids
8. Protection against photodamage
9. Repair of light-damaged PSII
10. New methodologies

As examples we show here the most important progress for topics 6 and 10. A full report with progress on all topics can be found in the Extended final publishable summary report, which can be downloaded from the project website (see below).

6. Photoregulation in cyanobacteria. HARVEST investigated the Orange Carotenoid Protein (OCP)-related photoprotective mechanism of cyanobacteria. One project characterized the Fluorescence Recovery Protein (FRP), one of the 3 essential elements for the mechanism that switches off the photoprotection, another project was to reconstitute in vitro the mechanism in full from induction to recovery using isolated proteins and complexes. This project combined biochemical, molecular biological and spectroscopic approaches and led to a detailed understanding of this process.

HARVEST also investigated alternative electron routes involved in photoprotection in Synechocystis sp. PCC6803. Funneling photosynthetic electron flow from water to target molecules by eliminating wasteful electron-transport routes without decreasing fitness of the cells is an important approach for future synthetic biology. In this project, we investigated the protective role of flavodiiron proteins (Flv) as a strong electron sink and revealed by various approaches that lack of the Flv1 and Flv3 proteins causes arrest of cell growth under fluctuating light. Importantly, these proteins are safeguarding Photosystem I (PSI) under fluctuating light and lack of these proteins results in strong damage and the malfunction of the PSI complex. On the other hand, Flv2 and Flv4 were found to be crucial for protection of Photosystem II (PSII) centers against photoinhibition. These proteins reduce the PSII excitation pressure by channeling up to 30% of PSII-originated electrons, and function in a complementary way with the above-mentioned OCP-related photoprotection.

10. New methodologies. HARVEST developed technology and experimental protocols for remote monitoring of plant growth and fitness performance. Early stress detection and monitoring of photosynthesis response to adverse conditions is an important trait assesed in plant breeding or greenhouse horticulture. Furthermore, the Membrane Inlet Mass Spectrometry (MIMS) system was optimized for online kinetic monitoring of photosynthetic performance in photosynthetic organisms in photobioreactors. The results of the MIMS analysis were used for understanding the photoregulation at the organism level and applied for light use and light adaptation modelling at We focused here on the evaluation of the inorganic carbon-concentrating mechanism in aquatic microorganisms during varying light conditions. These mechanisms raise the CO2 concentration at the intracellular carboxylating sites and thus compensate for the low affinity of RuBisCO for CO2, but they can also dissipate excess light energy through a futile cycle.

Contact details:
Dr. Jan P. Dekker, coordinator of HARVEST
VU University Amsterdam, Faculty of Sciences
De Boelelaan 1081, 1081 HV Amsterdam, The Netherlands
Ph: +31 20 5987931
HARVEST website: