The glaucocystophytes are a small group of photosynthetic, unicellular algae that possess cyanobacteria‐like plastids with prokaryotic peptidoglycans, coded in the cell nucleus; they are located on the base of the evolutionary tree towards higher plants.

Keywords: Cyanophora; Cyanoptyche; Glaucocystis; Gloeochaete; Glaucocystophyta; Peliaina; chloroplast evolution; cyanelle; cyanome; exogenosome; intertaxonic combination; metacyanome; muroplast; protoplastid; symbiosis

Figure 1.

Glaucocystophytes, morphology and size of cells and colonies. (a) C. paradoxa (9–16/7); (b) P. cyanea (N, but cyanelle (?) diameter about 5 μm); (c1) G. nostochinearum var. geitleri (more broad than long: 19–30/30–50); (c2) G. nostochinearum var. incrassata normal cell (16/23), developing eight‐autospore mother cell (23/29) (carmine acetic acid staining of nuclei); (c3) colony with six cells developed from an originally four‐autospore mother cell (two of the four autospores have already divided again, now by normal mitotic bipartition); (d) G. wittrockiana: (d1) zoospore (N), (d2) vegetative cell, and (d3) colony with eight vegetative cells (11–32), in the inferior cell series the pseudocilia have been removed; (e) C. gloeocystis f. dispersa: (e1) zoospore (32–44/21–23) and (e2) colony with four vegetative cells (24–36/17–22); the other four sister cells were split off. (Drawn after micrographs of Kies, , (d, e), Hanf and Schenk (a, c1, c3), Schnepf et al., (c2), and a sketch of Pascher, (b)). Numbers in parentheses are size limits (μm) of cells in relation to the cell axis: left numbers length/right numbers width (if one number then average value; N, size not given); a, anterior flagellum; b, mucilage body; c, centroplasm; f, flagellar groove; l, lipid droplet, m, muroplast or cyanelle; m’, muroplast digested; n, nucleus; p, pseudocilium; s, starch grain; v, pulsating vacuole; w, cell wall (of mother cell); w1, w2, w3, cell wall of first, second and third generation.

Figure 2.

Phylogenetic dendrograms. (a) Phylogeny of eukaryotes based on small subunit ribosomal RNA (SS‐rRNA) sequence comparison, inferred by the maximum‐likelihood method and rooted within the branch leading to Dictyostelium discoideum. The branch of glaucocystophytes represents the cluster of C. paradoxa, G. nostochinearum and G. wittrockiana, that of nucleomorphs contains the SS‐rRNA sequences of chlorarachniophytan and cryptophytan nucleomorphs. The dotted lines each represent a cluster and give the limits between shortest and longest branch lengths of the combined homologue sequences (drawn and greatly simplified after Bhattacharya et al., ). (b) Plastid phylogeny deduced from about 11 000 amino acid positions of 45 orthologous proteins common to the investigated plastomes and to the genome of the cyanobacterium Synechocystis PCC 6803, used as root (drawn and altered after Martin et al., ). The genomic levels of both the organismic (a) and the organellar (b) seem to support the idea that the phylogenetic branching position of glaucocystophytes is located near the evolutionary base of all eukaryotic photoautotrophic organisms.



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Further Reading

Cavalier‐Smith T and Lee JJ (1985) Protozoa as hosts for endosymbioses and the conversion of symbionts into organelles. Journal of Protozoology 32: 376–379.

Floener L and Bothe H (1983) The mutual relationship betweeen Cyanophora paradoxa and its cyanelles. In: Schenk HEA and Schwemmler W (eds) Endocytobiology, vol. 2, pp. 471–474. Berlin: De Gruyter.

Helmchen TA, Bhattacharya D and Melkonian M (1995) Analyses of ribosomal RNA sequences from Glaucocystophyte cyanelles provide new insights into the evolutionary relationships of plastids. Journal of Molecular Evolution 41: 203–210.

Herdman M and Stanier RY (1977) The cyanelle: chloroplast or endosymbiotic prokaryote? FEMS 1: 7–12.

Jakowitsch J, Neumann‐Spallart C, Ma Y et al. (1996) In vitro import of pre‐ferredoxin‐NADP+‐oxidoreductase from Cyanophora paradoxa into cyanelles and into pea chloroplasts. FEBS Letters 381: 153–155.

Pfanzagl B, Allmaier G, Schmid ER, De Pedro MA and Loeffelhardt W (1996) N‐Acetylputrescine as a characteristic constituent of cyanelle peptidoglycan in glaucocystophyte algae. Journal of Bacteriology 178: 6994–6997.

Schenk HEA (1994) Glaucocystophyta model for symbiogenous evolution of new eukaryotic species. In: (ed.) Seckbach J Developments of Hydrobiology, vol. 91: Evolutionary Pathways and Enigmatic Algae, pp. 19–52. Dordrecht: Kluwer Academic Publishers.

Schenk HEA, Bayer MG, Maier TL et al. (1992) Ferredoxin‐NADP+‐oxidoreductase of Cyanophora paradoxa nucleus encoded, but cyanobacterial gene transfer from symbiont to host, an evolutionary mechanism originating new species. Zeitschrift für Natur forschung 47c: 387–393.

Schlichting R, Zimmer W and Bothe H (1990) Exchange of metabolites in Cyanophora paradoxa and its cyanelles. Botanica Acta 103: 392–398.

Scott OT, Castenholz RW and Bonnett HT (1984) Evidence for a peptidoglycan envelope in the cyanelles of Glaucocystis nostochinearum Itzigsohn. Archives of Microbiology 139: 130–138.

Trench RK (1981) Chloroplasts: presumptive and de facto organelles. Annals of the New York Academy of Sciences 361: 341–355.

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Schenk, Hainfried EA(Jun 2001) Glaucocystophytes. In: eLS. John Wiley & Sons Ltd, Chichester. [doi: 10.1038/npg.els.0003061]