Light drives photosynthesis, however its influence on growth of plants is complex due to the highly variable light intensity in natural environment. At full sunlight, the radiation influx is too large to be handled. Plants have then evolved photoprotection mechanisms (PMs) to dissipate excess light (EL) energy, thus avoiding photo-damage of the chloroplast.
Operation of PMs is crucial to allow plants to use light efficiently. Thus, PMs are a key target for improving the performance of crop plants: enhanced energy dissipation could confer greater abiotic stress resistance, but their constitutive activation leads to low rates of growth, therefore plants in stable environments (e.g. glasshouses) could benefit from switching off PMs. A deeper comprehension of the molecular basis of PMs, and how light-use efficiency can be optimized, is essential if we are to use intelligent strategies for manipulating photosynthetic efficiency in crop plants.
We will tackle this problem by a multidisciplinary approach, combining the knowledge on genetics and biochemistry of pigment-proteins with techniques of femtosecond transient absorption spectroscopy. Most of these PMs take place in the antenna proteins of the thylakoids. We will characterize A. thaliana knock-out lines, lacking specific antenna complexes or carrying mutated isoforms. Analysis of excitation energy transfer efficiency on purified photosystems (PS) will allow the ultrafast energy deactivation mechanisms to be identified. In particular, we will investigate (i) the Non-Photochemical Quenching mechanism, which dissipate over 80% of absorbed photons by PSII as heat in EL; (ii) the reddest spectral forms of the PSI antenna, which are supposed to prevent photodamage. Molecular fundaments of such PMs still remain unclear for both photosystems.
Potential technological exploitations of results are related to the production of 2nd generation biofuels and to the identification of candidate genes for agricultural applications