期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 112, 期 18, 页码 5767-5772出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1423400112
关键词
organelle loss; plastid loss; endosymbiosis; plastid metabolism; diaminopimelate aminotransferase
资金
- Australian Research Council (ARC) [DP130100572, DP1093395]
- King Abdullah University of Science and Technology Faculty Baseline Research Fund
- Victorian Life Sciences Computation Initiative [VR0254]
- Science Foundation Ireland [13/SIRG/2125]
- Australia Award
- ARC Centre of Excellence in Plant Cell Walls Grant [CE110001007]
- National Health and Medical Research Council
- Australian Research Council [DP1093395] Funding Source: Australian Research Council
- Science Foundation Ireland (SFI) [13/SIRG/2125] Funding Source: Science Foundation Ireland (SFI)
Organelle gain through endosymbiosis has been integral to the origin and diversification of eukaryotes, and, once gained, plastids and mitochondria seem seldom lost. Indeed, discovery of nonphotosynthetic plastids in many eukaryotes-notably, the apicoplast in apicomplexan parasites such as the malaria pathogen Plasmodiumhighlights the essential metabolic functions performed by plastids beyond photosynthesis. Once a cell becomes reliant on these ancillary functions, organelle dependence is apparently difficult to overcome. Previous examples of endosymbiotic organelle loss (either mitochondria or plastids), which have been invoked to explain the origin of eukaryotic diversity, have subsequently been recognized as organelle reduction to cryptic forms, such as mitosomes and apicoplasts. Integration of these ancient symbionts with their hosts has been too well developed to reverse. Here, we provide evidence that the dinoflagellate Hematodinium sp., a marine parasite of crustaceans, represents a rare case of endosymbiotic organelle loss by the elimination of the plastid. Extensive RNA and genomic sequencing data provide no evidence for a plastid organelle, but, rather, reveal a metabolic decoupling from known plastid functions that typically impede organelle loss. This independence has been achieved through retention of ancestral anabolic pathways, enzyme relocation from the plastid to the cytosol, and metabolic scavenging from the parasite's host. Hematodinium sp. thus represents a further dimension of endosymbiosis-life after the organelle.
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