Mechanistic insights into the function of the ancient light-harvesting protein LHCSR3 in light energy dissipation in Chlamydomonas reinhardtii

Basic data for this project

Description

Light is essential for photosynthesis but excess photons must be de-excited to avoid photodamage. In plants the fastest response to excess light is provided by a mechanism called non-photochemical quenching (NPQ). The most important constituent of NPQ is qE, which regulates the thermal dissipation of excess absorbed light energy and operates at a time scale of seconds to minutes. The qE capacity of C. reinhardtii is dependent on environmental conditions and is inducible by growth in high light. The qE capacity increases proportional with the light-dependent increase of the LHCSR3 protein. Deletion or depletion of LHCSR3 abolishes the ability of the cells to dissipate harmful excess energy, demonstrating that LHCSR3 is required for efficient qE. Despite the significant progress in the understanding of the qE, major questions remain unsolved such as: (i) what is the function of LHCSR1 in qE, (ii) where in the photosynthetic machinery are LHCSR1/3 localized, (iii) what are the proteinprotein- interaction partner(s), (iv) what is the stoichiometry of LHCSR1/3 with other LHC polypeptides and the photosynthetic reaction center and (v) do changes in membrane dynamics due to LHCSR1/3 depletion contribute to the operation of qE. We aim to address these questions by using reverse genetics, functional proteomics and spectroscopic technologies.