Photosynthetic light-harvesting, regulation and carotenoids: A theoretical perspective

Dr Chris Duffy, Queen Mary University of London.

Plant light-harvesting proteins are exemplary solar devices. Normally operating at near total efficiency, they supply the organism with an optimal and consistent input of energy in very poor light. More remarkably these proteins can regulate this efficiency in response to light-environment, rapidly switching from a light-harvesting mode to a protective one, trapping and quenching excess energy to prevent oxidative damage in high light. It has recently been shown that this ‘photoprotective switch’ is one of the key factors determining crop yield and viability. However, the mechanics of this switch, the physics of energy quenching and how the switch is coupled to the changing light environment have eluded purely experimental approaches.

My research is focussed on understanding the ‘other’ photosynthetic pigments: the carotenoids. These pigments have been suggested as central factors in the photoprotective switch although their optically dark, highly dissipative and electronically complex nature means this is largely hypothetical.  My group has focussed on under-standing the role of the carotenoids in light-harvesting proteins using structure-based simulation of energy transfer and dissipation. We have developed the first molecular picture of the photoprotective switch in which the carotenoids act as quenchers of excess energy, controlled by a fine conformational switch which modulates chlorophyll-carotenoid energy exchange. Moreover, we have recently shown that this protective mechanism appears to be a general feature of plant light-harvesting proteins, with no particular protein, pathway or pigment being a requirement for effective protection.

By understanding how this regulatory function operates at the molecular level and how the carotenoids, pigments with seemingly none of the prerequisite properties of an efficient light-harvester, fit within the scheme of light collection opens up possibilities of optimization and mimicry.   

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