On the prokaryotic nature of red algal chloroplasts.

Abstract

The sequences of oligonucleotides released by TI ribonuclease digestion of 32P-labeled 16S (chloroplast) and 18S (cytoplasmic) ribosomal RNAs from a marine species of Porphyridium (Rhodophyta) have been determined. The resultant catalogs have been compared to those obtained for three prokaryotes: Escherichia coli, Bacillus subtilis, and Anacystis nidulans (a blue-green alga). There is extensive sequence homology between the Porphyridium chloroplast 16S ribosomal RNA and each of the prokaryotic 16S ribosomal RNAs, but little homology between the Porphyridium cytoplasmic 18S ribosomal RNA and any of the 16S species. These data provide a measure of the evolutionary distance separating existing chloroplasts from contemporary bacteria and blue-green algae, and are discussed in terms of the hypothesis that these organelles evolved from endosymbiotic photosynthetic prokaryotes.The notion that modern chloroplasts evolved from endosymbiotic prokaryotes (perhaps resembling blue-green algae) is an old one (1) which has gained considerable modern support (2-4), since the discovery of DNA in these semi-autonomous, self-replicating organelles (5). The argument rests on structural resemblances between chloroplasts and prokaryotic cells, strong similarities in structure and function between chloroplast and prokaryotic ribosomes (6), near identity of the pathways of photosynthetic electron flow and CO2 fixation in chloroplasts and blue-greens, and the existence of modern true endosymblonts resembling the postulated ancestral endosymbiotic prokaryotes (2, 3). None of these types of evidence submits to quantitative analysis, and none can provide any measure of the evolutionary distance between contemporary chloroplasts and prokaryotes. It is thus still possible to maintain [as Klein (7) and Allsopp (8)

The preliminary sequence of tRNAMetF from Anacystis nidulans compared with other initiator tRNAs

“…It would seem from this data that taxonomically E. coli and Bacillus are more related to each other than to blue-green algae. This hypothesis is in disagreement with results obtained from the T1 RNase-generated catalogs of ribosomal RNA showing a closer relationship between algae and Bacillus than between Bacillus and E. coli [22]. It should be noted, however, that both hypotheses assume a relatively constant fixation rate of mutations for each class of RNA.…”

Confirmation of soybean plastid rRNAs by formaldehyde denaturing agarose gel electrophoresis

“…According to the endosymbiosis theory, plastids originated from eubacteria-like cells that had invaded and then lived within primitive eukaryotic hosts (Bonen and Doolittle, 1975;Schwarz and Kössel, 1980). Gradually, they became an important group of plant cellular organelles with essential functions (McFadden, 2001).…”

Cladistic analysis of blue‐green procaryote interrelationships and chloroplast origin based on 16S rRNA oligonucleotide catalogues

“…There was a revolution in the understanding of procaryote phylogeny (Fox et al, 1980;Stackebrandt and Woese, 1981); recent discussions are, for example, Hespell et al, 1984;Paster et al, 1984;Woese et al, 1984Woese et al, , 1985Gibson et al, 1985 andFowler et al, 1986. Boncn, Doolittle, and collaborators (Doolittle et al, 1975;Doolittle, 1976, 1978;Bonen et al, 1979) assembled catalogues from several blue-green procaryotes;…”

“…Using oligonucleotide catalogues they addressed also the question of red algal (Porphyridium) chloroplast origin (Bonen and Doolittle, 1975;Bonen et al, 1979). Zablen et al (197.5) similarly discussed the origin of the Euglena chloroplast.…”

“…First; the blue-greens are procaryotes (Doolittle et al, 1975;Bonen and Doolittle, 1976). Second; the chloroplasts of Euglena and Porphyridium (and by implication chloroplasts in general) are procaryotic in nature, and originated probably by endosymbiosis Doolittle, 1975, 1976;Zablen et al, 1975;Bonen et al, 1979).…”