Resumen
Nonphotosynthetic plastids retain important biological functions and are indispensable for cell viability. However, the detailed processes underlying the loss of plastidal functions other than photosynthesis remain to be fully understood. In this study, we used transcriptomics, subcellular localization, and phylogenetic analyses to characterize the biochemical complexity of the nonphotosynthetic plastids of the apochlorotic diatom Nitzschia sp. NIES-3581. We found that these plastids have lost isopentenyl pyrophosphate biosynthesis and ribulose-1,5-bisphosphate carboxylase/oxygenase-based carbon fixation but have retained various proteins for other metabolic pathways, including amino acid biosynthesis, and a portion of the Calvin-Benson cycle comprised only of glycolysis/gluconeogenesis and the reductive pentose phosphate pathway (rPPP). While most genes for plastid proteins involved in these reactions appear to be phylogenetically related to plastid-targeted proteins found in photosynthetic relatives, we also identified a gene thatmost likely originated from a cytosolic protein gene. Based on organellar metabolic reconstructions of Nitzschia sp. NIES-3581 and the presence/absence of plastid sugar phosphate transporters, we propose that plastid proteins for glycolysis, gluconeogenesis, and rPPP are retained even after the loss of photosynthesis because they feed indispensable substrates to the amino acid biosynthesis pathways of the plastid. Given the correlated retention of the enzymes for plastid glycolysis, gluconeogenesis, and rPPP and those for plastid amino acid biosynthesis pathways in distantly related nonphotosynthetic plastids and cyanobacteria, we suggest that this substrate-level link with plastid amino acid biosynthesis is a key constraint against loss of the plastid glycolysis/gluconeogenesis and rPPP proteins in multiple independent lineages of nonphotosynthetic algae/plants.
Idioma original | English |
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Páginas (desde-hasta) | 2355-2366 |
Número de páginas | 12 |
Publicación | Molecular Biology and Evolution |
Volumen | 34 |
N.º | 9 |
DOI | |
Estado | Published - sep. 2017 |
Nota bibliográfica
Funding Information:This work was supported, in part by grants from the Japan Society for Promotion of Sciences (15H05606 and 15H14591 awarded to R.K., 23117006 and 16H04826 awarded to Y.I., 15H05231 awarded to T.H., and 26840123 awarded to G.T.), the Natural Sciences and Engineering Research Council of Canada (J.M.A.). This work was also supported, in part by Showa Seitoku Memorial Foundation (R.K.).
Publisher Copyright:
© The Author 2017.
ASJC Scopus Subject Areas
- Ecology, Evolution, Behavior and Systematics
- Molecular Biology
- Genetics
PubMed: MeSH publication types
- Journal Article
- Research Support, Non-U.S. Gov't