(1) Institute of Biology III, University of Freiburg, Schaenzlestrasse 1, 79104 Freiburg, Germany
Abstract:
Genetic and physiological studies have to-date revealed evidence for five signaling pathways by which the chloroplast exerts
retrograde control over nuclear genes. One of these pathways is dependent on product(s) of plastid protein synthesis, for
another the signal is singlet oxygen, a third employs chloroplast-generated hydrogen peroxide, a fourth is controlled by the
redox state of the photosynthetic electron transport chain, and a fifth involves intermediates and possibly proteins of tetrapyrrole
biosynthesis. These five pathways may be part of a complex signaling network that links the functional and physiological state
of the chloroplast to the nucleus. Mutants defective in various steps of photosynthesis reveal a surprising diversity in nuclear
responses suggesting the existence of a complex signaling network.