Molecular organization and expression of the plastid genome of Galdieria sulphuraria (= Cyanidium caldarium) and other unicellular red algae

Abstract

The hypothesis of the endosymbiotic origin of plastids is now generally accepted. An overwhelm ing abundance of cytological, biochemical and especially molecular data are in favor of this hypothesis. Nevertheless several basic questions remain to be settled as for example whether the present different types of plastids (plastids of chlorophytes, rhodophytes, chromophytes, cryptophytes etc.) can be traced back to an unique endosymbiotic event (monophyletic origin) or whether the different plastids are the products of multiple endosymbiotic events (polyphyletic origin) and further what may be the relation between the different types of plastids. For a decision on this problem one has to compare data about the coding capacity, the structure and the sequence of the genomes of the different types of plastids. While many data are available in this respect for the plastids of higher plants and green algae (plastids of chlorophyll a/b plants-chloroplasts) almost nothing was known until a short time ago about the genome of the plastids of red algae (rhodoplasts).