Abstract
It is not yet entirely clear how grana stacks are formed, and several models had been proposed, such as the disk piled model, the helical model, and so on. The Arabidopsis mutant pcb2, which is deficient in divinyl protochlorophyllide 8-vinyl reductase, not only accumulates divinyl chlorophylls instead of chlorophylls but also lacks distinctive grana stacks. In general, LHC II complexes are believed to be involved in the development of the grana stacks, and the LHC II complexes in the pcb2 have an abnormality. This abnormality may be explained by the altered chlorophyll-protein interaction caused by the difference of molecular structures between divinyl chlorophyll and normal chlorophyll. In addition, the decreased number of granal layers and their abnormal radius in pcb2 provided new insight to the mechanism that maintains the cylindrical shape of grana stacks. We discuss a new model of grana stack formation.
