How plants regulate their photosynthesis
The question of how plant photosynthesis is adapted to fluctuations in climate is a controversial one. Researchers at Linköping University are now able to show how plants regulate the process by modifying proteins in the cells.
The results are published in the prestigious journal Plant Cell.
Photosynthesis is the complex process by which green plants and algae use energy derived from light to produce sugar, water and carbon dioxide.
Chloroplasts are chemical factories inside cells where the photosynthesis takes place. The green chlorophyll is attached to long membrane systems, tylakoids, which in order to fit inside the chloroplasts form structures resembling stacks of coins. These so-called grana structures are changeable which allows the photosynthesis to function efficiently even when there are variations in climate.
However, how plants regulate the membrane structure, how it is maintained and what determines the size has so far been unknown.
Professor Alexander V. Vener and his research team in Cell Biology at the Department of Clinical and Experimental Medicine now show that there is a specific protein modification, phosphorylation, behind this dynamics. Phosphorylation, in which one or more phosphate groups bind to the protein, is the most common form of internal signalling in all organisms.
The scientists used the plant Thale Cress (Arabidopsis Thaliana) as a model. A mutant variant lacking the enzyme which triggers phosphorylation, kinases, was compared with wild specimens of same species. When the enzyme was not active the mutant variant formed abnormally large stacks of grana. The dynamics within the membranes stopped and necessary processes of adaption were affected.
This is the explanation as to why previous research has shown that mutant Thale Cress seedlings produce 41 per cent fewer seeds than normal seedlings of the same plant type.
The conclusion of the study, which was carried out in collaboration with colleagues in Geneva, Switzerland, is that the phosphorylation of membrane proteins affects the macroscopic structure of the photosynthetic membrane, which allows plants to adapt to different climate conditions.
Image: The structure of the photosynthetic membrane in the normal plant (left) and the mutant variant which lacks phosphorylation (right).
Article: Phosphorylation of Photosystem II controls functional macroscopic folding of photo synthetic membranes in Arabidopsis by Richard Fristedt, Adrian Willig, Pontus Granath, Michèle Crèvecoeur, Jean-David Rochaix and Alexander V. Vener. Plant Cell Preview, December 2009.
Alexander V. Vener, Professor of Cell Biology, +46 13 22 40 50, alexander.vener @ liu.se
Richard Fristedt, PhD student in Medical Cell Biology, +46 13 22 51 33, +46 73 904 73 74, rikard.fristedt @ liu.se
Last updated: 2010-01-08