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Open Biol. 2016 Nov;6(11). pii: 160249.

The plastid genome of some eustigmatophyte algae harbours a bacteria-derived six-gene cluster for biosynthesis of a novel secondary metabolite.

Author information

1
Faculty of Science, Department of Biology and Ecology, Life Science Research Centre, University of Ostrava, Chittussiho 10, 710 00 Ostrava, Czech Republic.
2
Faculty of Science, Institute of Environmental Technologies, University of Ostrava, Chittussiho 10, 710 00 Ostrava, Czech Republic.
3
Institute of Molecular Genetics of the ASCR, v. v. i., Prague, Czech Republic.
4
Faculty of Science, Department of Biology and Ecology, Life Science Research Centre, University of Ostrava, Chittussiho 10, 710 00 Ostrava, Czech Republic marek.elias@osu.cz.

Abstract

Acquisition of genes by plastid genomes (plastomes) via horizontal gene transfer (HGT) seems to be a rare phenomenon. Here, we report an interesting case of HGT revealed by sequencing the plastomes of the eustigmatophyte algae Monodopsis sp. MarTras21 and Vischeria sp. CAUP Q 202. These plastomes proved to harbour a unique cluster of six genes, most probably acquired from a bacterium of the phylum Bacteroidetes, with homologues in various bacteria, typically organized in a conserved uncharacterized putative operon. Sequence analyses of the six proteins encoded by the operon yielded the following annotation for them: (i) a novel family without discernible homologues; (ii) a new family within the superfamily of metallo-dependent hydrolases; (iii) a novel subgroup of the UbiA superfamily of prenyl transferases; (iv) a new clade within the sugar phosphate cyclase superfamily; (v) a new family within the xylose isomerase-like superfamily; and (vi) a hydrolase for a phosphate moiety-containing substrate. We suggest that the operon encodes enzymes of a pathway synthesizing an isoprenoid-cyclitol-derived compound, possibly an antimicrobial or other protective substance. To the best of our knowledge, this is the first report of an expansion of the metabolic capacity of a plastid mediated by HGT into the plastid genome.

KEYWORDS:

Eustigmatophyceae; UbiA superfamily; horizontal gene transfer; plastid genome; secondary metabolism; sugar phosphate cyclase superfamily

PMID:
27906133
PMCID:
PMC5133447
DOI:
10.1098/rsob.160249
[Indexed for MEDLINE]
Free PMC Article

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