Membranes on the move: How plants sense and respond to changing levels of sunlight
New research published this week in Plant Physiology by University of Sheffield scientists has revealed how the photosynthetic membranes in leaves respond to changes in light intensity and spectral quality to optimise photosynthesis.
The new insights, based on remarkable images provided by sub-diffraction structured illumination fluorescence microscopy conducted at the University’s Wolfson Light Microscopy Facility suggest that morphological changes in photosynthetic membranes play a major role in adaptation to fluctuating light intensity.
Life on earth depends on photosynthesis, the source of our food, oxygen and most of our energy. Photosynthesis involves conversion of light into chemical energy in the photosynthetic membranes in chloroplasts, which can then be used to convert carbon dioxide into biomass. Fluctuations in light intensity and spectral quality caused by variable cloud cover and the diurnal cycle perturb plant metabolism, leading to mismatches between the amount of light absorbed and that which can be used in photosynthesis. Left unchecked such imbalances can damage plants reducing their productivity.
The new research led by Dr Matt Johnson in the Department of Molecular Biology and Biotechnology used structured illumination microscopy to show how plants respond to fluctuations in sunlight by modifying the organisation of their photosynthetic membranes to optimise the utilisation of light by photosynthesis and avoid damage. Moreover they discovered that two crucial proteins STN7 and TAP38, which act antagonistically, are critical in allowing plants to track and respond to light levels.
Dr Johnson explains “Our imaging shows that the photosynthetic membrane can change its size and shape in response to light levels. The two proteins responsible, STN7 and TAP38 controlled these dynamics by changing the net charge on the membranes, the more charges that cover the surface the less they want to stick together in stacks. By controlling the amount of membranes arranged in stacks, plants can control the amount of light they channel in photosynthesis and the amount they dissipate as heat to protect themselves.”
“Manipulating the efficiency with which plants transition between photosynthesis and photoprotection has already been shown to have a tangible effect on crop yields. The added understanding brought by this work could therefore provide further clues on how we can grow more food to feed a growing population and produce more biofuels from plants and algae to meet future energy need.”
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