Moving the green: CHUP1 and chloroplast movement-An obvious relationship?

Chloroplast movement as a response of plants to light variations is presented as an example in each classical textbook, showing that these organelles accumulate in response to low light and avoid high light irradiation. In sharp contrast to the morphological discovery of the phenomenon, which dates back more than a century, the molecular understanding of this effect is just at its beginning and only recently first components of the signal cascade initiating this process were described. Among these, a protein termed CHUP1 was identified. This protein is present in the outer membrane of chloroplasts and thereby discussed as the first component of a possible 'moving ensemble' assembling at the 'moved cargo'. The protein is able to interact with actin and profilin-and even more, is able to regulate this interaction in vitro. Thereby, today it can be stated that actin filament reformation and chloroplast repositioning are coordinated if not dependent on each other.