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- Crona, Mikael, et al.
(författare)
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A Rare Combination of Ribonucleotide Reductases in the Social Amoeba Dictyostelium discoideum
- 2013
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Ingår i: Journal of Biological Chemistry. - 0021-9258 .- 1083-351X. ; 288:12, s. 8198-8208
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Tidskriftsartikel (refereegranskat)abstract
- Ribonucleotide reductases (RNRs) catalyze the only pathway for de novo synthesis of deoxyribonucleotides needed for DNA replication and repair. The vast majority of eukaryotes encodes only a class I RNR, but interestingly some eukaryotes, including the social amoeba Dictyostelium discoideum, encode both a class I and a class II RNR. The amino acid sequence of the D. discoideum class I RNR is similar to other eukaryotic RNRs, whereas that of its class II RNR is most similar to the monomeric class II RNRs found in Lactobacillus spp. and a few other bacteria. Here we report the first study of RNRs in a eukaryotic organism that encodes class I and class II RNRs. Both classes of RNR genes were expressed in D. discoideum cells, although the class I transcripts were more abundant and strongly enriched during mid-development compared with the class II transcript. The quaternary structure, allosteric regulation, and properties of the diiron-oxo/radical cofactor of D. discoideum class I RNR are similar to those of the mammalian RNRs. Inhibition of D. discoideum class I RNR by hydroxyurea resulted in a 90% reduction in spore formation and decreased the germination viability of the surviving spores by 75%. Class II RNR could not compensate for class I inhibition during development, and an excess of vitamin B12 coenzyme, which is essential for class II activity, did not improve spore formation. We suggest that class I is the principal RNR during D. discoideum development and growth and is important for spore formation, possibly by providing dNTPs for mitochondrial replication.
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- Nystedt, Björn, et al.
(författare)
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The Norway spruce genome sequence and conifer genome evolution
- 2013
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Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 497:7451, s. 579-584
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Tidskriftsartikel (refereegranskat)abstract
- Conifers have dominated forests for more than 200 million years and are of huge ecological and economic importance. Here we present the draft assembly of the 20-gigabase genome of Norway spruce (Picea abies), the first available for any gymnosperm. The number of well-supported genes (28,354) is similar to the >100 times smaller genome of Arabidopsis thaliana, and there is no evidence of a recent whole-genome duplication in the gymnosperm lineage. Instead, the large genome size seems to result from the slow and steady accumulation of a diverse set of long-terminal repeat transposable elements, possibly owing to the lack of an efficient elimination mechanism. Comparative sequencing of Pinus sylvestris, Abies sibirica, Juniperus communis, Taxus baccata and Gnetum gnemon reveals that the transposable element diversity is shared among extant conifers. Expression of 24-nucleotide small RNAs, previously implicated in transposable element silencing, is tissue-specific and much lower than in other plants. We further identify numerous long (>10,000 base pairs) introns, gene-like fragments, uncharacterized long non-coding RNAs and short RNAs. This opens up new genomic avenues for conifer forestry and breeding.
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