Chloroplasts, the site of the primary reactions of photosynthesis, are
organelles capable of independent protein synthesis, but which depend on
the nucleus for most polypeptides. The process of photosynthesis is
especially sensitive to environmental conditions and the composition of
the photosynthetic apparatus can be modulated in response to
environmental change. This acclimation process requires close
communication between chloroplast and nucleus. Here we present evidence
that the form in which carbon is exported from the chloroplast encodes
information about the metabolic status of the photosynthetic apparatus
which in turn controls photosynthetic acclimation.