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| CRYPTOMONAD ALGAE ARE EVOLUTIONARY CHIMERAS OF 2 PHYLOGENETICALLY DISTINCT UNICELLULAR EUKARYOTES |
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| Author(s): DOUGLAS SE, MURPHY CA, SPENCER DF, GRAY MW |
| Source: NATURE Volume: 350 Issue: 6314 Pages: 148-151 Published: MAR 14 1991 |
| Times Cited: 209 References: 27 |
| Abstract: ALTHOUGH it is widely accepted that the plastids of plants and algae originated as endosymbionts 1, the details of this evolutionary process are unclear 2,3. It has been proposed that in organisms whose plastids are surrounded by more than two membranes, the endosymbiont was a eukaryotic alga rather than a photosynthetic prokaryote 4. The DNA-containing 5 nucleomorph 6 of cryptomonad algae appears to be the vestigial nucleus of such an algal endosymbiont 7. Eukaryotic-type ribosomal RNA sequences have been localized to a nucleolus-like structure in the nucleomorph 8. In support of the hypothesis that cryptomonads are evolutionary chimaeras of two distinct eukaryotic cells, we show here that Cryptomonas PHI contains two phylogenetically separate, nuclear-type small-subunit rRNA genes, both of which are transcriptionally active. We incorporate our rRNA sequence data into phylogenetic trees, from which we infer the evolutionary ancestry of the host and symbiont components of Cryptomonas PHI. Such trees do not support the thesis 3 that chromophyte algae evolved directly from a cryptomonad-like ancestor. |
| Document Type: Article |
| Language: English |
| Reprint Address: DOUGLAS, SE (reprint author), NATL RES COUNCIL CANADA, ATLANTIC REG LAB, INST MARINE BIOSCI, 1411 OXFORD ST, HALIFAX B3H 3Z1, NS CANADA |
Addresses:
1. DALHOUSIE UNIV, DEPT BIOCHEM, HALIFAX B3H 4H7, NS CANADA |
| Publisher: MACMILLAN MAGAZINES LTD, 4 LITTLE ESSEX STREET, LONDON, ENGLAND WC2R 3LF |
| Subject Category: Multidisciplinary Sciences |
| IDS Number: FB645 |
| ISSN: 0028-0836 |
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