title: Function and evolution of grana.
abstract: Chloroplasts are descended from cyanobacteria, and they retain many features of the cyanobacterial photosynthetic apparatus. However, land-plant chloroplasts have a strikingly different thylakoid membrane organization to that of cyanobacteria. Usually the two photosystems are laterally segregated; Photosystem II is concentrated in complex stacked-membrane structures known as grana. The function of grana has long been debated. Recent studies on membrane organization in chloroplasts, cyanobacteria and purple bacteria now offer a new perspective. I argue that grana allow the presence of a large light-harvesting antenna for Photosystem II, without excessively restricting electron transport. Other organisms solve this problem in different ways. Land plants evolved from macroalgae that were adapted to high light conditions; they evolved grana as a new solution to the problem of efficient photosynthesis in shade.
authors.affiliation: School of Biological and Chemical Sciences, Queen Mary, University of London, Mile End Road, London E1 4NS, UK. c.mullineaux@qmul.ac.uk
authors.forename: Conrad W
authors.initials: CW
authors.lastname: Mullineaux
mesh_terms: D005075:Biological Evolution; D002736:Chloroplasts / Q000502:physiology*; D000458:Cyanobacteria / Q000502:physiology / Q000648:ultrastructure; D010788:Photosynthesis; D020524:Thylakoids / Q000502:physiology / Q000648:ultrastructure*