[Regulation of the synthesis of plastid proteins in Euglena gracilis]

The discovery of plastid-to-nucleus retrograde signaling-a personal perspective

DNA and machinery for gene expression have been discovered in chloroplasts during the 1960s. It was soon evident that the chloroplast genome is relatively small, that most genes for chloroplast-localized proteins reside in the nucleus and that chloroplast membranes, ribosomes, and protein complexes are composed of proteins encoded in both the chloroplast and the nuclear genome. This situation has made the existence of mechanisms highly probable that coordinate the gene expression in plastids and nucleus. In the 1970s, the first evidence for plastid signals controlling nuclear gene expression was provided by studies on plastid ribosome deficient mutants with reduced amounts and/or activities of nuclear-encoded chloroplast proteins including the small subunit of Rubisco, ferredoxin NADP+ reductase, and enzymes of the Calvin cycle. This review describes first models of plastid-to-nucleus signaling and their discovery. Today, many plastid signals are known. They do not only balance gene expression in chloroplasts and nucleus during developmental processes but are also generated in response to environmental changes sensed by the organelles.

On the developmental dependence between Cyanophora paradoxa and Cyanocyta korschikoffiana in symbiosis : Host-dependent development of endocyanelles

The prokaryote Cyanocyta korschikoffiana was isolated from the eukaryote Cyanophora paradoxa. The synthesis of several thylakoid proteins in these cyanelles is influenced by light and darkness and is sensitive to cycloheximide, the inhibitor of the eukaryotic host's translation. The possibility of a direct coordination between the translations of the host and of the cyanelles is discussed.