Roger Hangarter, Indiana University, Function and mechanism of light-induced chloroplast movements in leaf cells

Light-dependent chloroplast movements function to optimize light absorption in photosynthetic cells. Under high light intensity chloroplasts migrate to the anticlinal sides of leaf cells and in low light the chloroplast migrate to the periclinal sides. This repositioning of chloroplasts is stimulated by the plasma membrane-associated phototropin photoreceptors. Chloroplast movements appear to be driven by actin re-organization at the plasma membrane. I will discuss how chloroplast movements dynamically affect the optical properties of leaves to fine-tune photosynthesis. In addition, results will be presented showing that the plasma membrane-associated protein, Thrumin1, is required for normal chloroplast movement and functions in reorganization of the cortical actin cytoskeleton during light-dependent chloroplast movements.