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Comparative analysis of the 5S rRNA and its associated proteins reveals unique primitive rather than parasitic features in Giardia lamblia.

Feng JM, Sun J, Xin DD, Wen JF - PLoS ONE (2012)

Bottom Line: Eukaryotic 5S rRNA and its associated proteins (5S rRNA system) have become very well understood.By collecting and confirming pre-existing data and identifying new data, we obtained almost complete datasets of the system of three isolates of G. lamblia, two other parasitic excavates (Trichomonas vaginalis, Trypanosoma cruzi), and one free-living one (Naegleria gruberi).Our results also imply G. lamblia might be a primitive eukaryote with secondary parasitically-degenerated features.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, People's Republic of China.

ABSTRACT

Background: 5S rRNA is a highly conserved ribosomal component. Eukaryotic 5S rRNA and its associated proteins (5S rRNA system) have become very well understood. Giardia lamblia was thought by some researchers to be the most primitive extant eukaryote while others considered it a highly evolved parasite. Previous reports have indicated that some aspects of its 5S rRNA system are simpler than that of common eukaryotes. We here explore whether this is true to its entire system, and whether this simplicity is a primitive or parasitic feature.

Methodology/principal findings: By collecting and confirming pre-existing data and identifying new data, we obtained almost complete datasets of the system of three isolates of G. lamblia, two other parasitic excavates (Trichomonas vaginalis, Trypanosoma cruzi), and one free-living one (Naegleria gruberi). After comprehensively comparing each aspect of the system among these excavates and also with those of archaea and common eukaryotes, we found all the three Giardia isolates to harbor a same simplified 5S rRNA system, which is not only much simpler than that of common eukaryotes but also the simplest one among those of these excavates, and is surprisingly very similar to that of archaea; we also found among these excavates the system in parasitic species is not necessarily simpler than that in free-living species, conversely, the system of free-living species is even simpler in some respects than those of parasitic ones.

Conclusion/significance: The simplicity of Giardia 5S rRNA system should be considered a primitive rather than parasitically-degenerated feature. Therefore, Giardia 5S rRNA system might be a primitive system that is intermediate between that of archaea and the common eukaryotic model system, and it may reflect the evolutionary history of the eukaryotic 5S rRNA system from the archaeal form. Our results also imply G. lamblia might be a primitive eukaryote with secondary parasitically-degenerated features.

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Sequence alignments of 5S rRNA genes of the three G. lamblia isolates.r0002, r0005, r0006, r0007, r0011, r0015, r0026, and r0008 represent the eight G. lamblia WB 5S rRNA genes. ACGJ01000259 (274–309) represents sequences from residue 274 to 309 of contig ACGJ01000259 in the G. lamblia GS genome. Box denotes the putative partial 5S rRNA gene identified in G. lamblia GS sharing 100% identity with 5′ fragment of 5S rRNA gene in G. lamblia WB and P15.
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pone-0036878-g001: Sequence alignments of 5S rRNA genes of the three G. lamblia isolates.r0002, r0005, r0006, r0007, r0011, r0015, r0026, and r0008 represent the eight G. lamblia WB 5S rRNA genes. ACGJ01000259 (274–309) represents sequences from residue 274 to 309 of contig ACGJ01000259 in the G. lamblia GS genome. Box denotes the putative partial 5S rRNA gene identified in G. lamblia GS sharing 100% identity with 5′ fragment of 5S rRNA gene in G. lamblia WB and P15.

Mentions: No putative 5S rRNA gene was identified in the G. lamblia GS genome database upon the retrieval of various 5S rRNA sequences from the 5S rRNA database as queries to BLASTn search against the genome database. However, one hit (Contig ID: ACGJ01000259), which was found to possess a 36 bp sequence sharing 100% identity with the 5′ terminal region (from+1 bp to 36 bp) of 5S rRNA genes of G. lamblia WB and P15 was found when the 5S rRNA genes of the two isolates were used as queries (Figure 1). The region in contig ACGJ01000259 (309 bp long) sharing 100% identity with 5S rRNA gene (from+1 bp to 36 bp) of G. lamblia WB and P15 was found at the end of this contig (from 274 bp to 309 bp). Moreover, a 79 bp RNA fragment sharing 99% identity with the 3′ terminal region (from +39 bp to +117 bp) of G. lamblia WB 5S rRNA was once reported in G. lamblia GS [21]. In this way, the lack of a G. lamblia 5S rRNA gene in the G. lamblia GS genome database is most probably due to the numerous gaps in the database and the small number genes in this organism.


Comparative analysis of the 5S rRNA and its associated proteins reveals unique primitive rather than parasitic features in Giardia lamblia.

Feng JM, Sun J, Xin DD, Wen JF - PLoS ONE (2012)

Sequence alignments of 5S rRNA genes of the three G. lamblia isolates.r0002, r0005, r0006, r0007, r0011, r0015, r0026, and r0008 represent the eight G. lamblia WB 5S rRNA genes. ACGJ01000259 (274–309) represents sequences from residue 274 to 309 of contig ACGJ01000259 in the G. lamblia GS genome. Box denotes the putative partial 5S rRNA gene identified in G. lamblia GS sharing 100% identity with 5′ fragment of 5S rRNA gene in G. lamblia WB and P15.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3369914&req=5

pone-0036878-g001: Sequence alignments of 5S rRNA genes of the three G. lamblia isolates.r0002, r0005, r0006, r0007, r0011, r0015, r0026, and r0008 represent the eight G. lamblia WB 5S rRNA genes. ACGJ01000259 (274–309) represents sequences from residue 274 to 309 of contig ACGJ01000259 in the G. lamblia GS genome. Box denotes the putative partial 5S rRNA gene identified in G. lamblia GS sharing 100% identity with 5′ fragment of 5S rRNA gene in G. lamblia WB and P15.
Mentions: No putative 5S rRNA gene was identified in the G. lamblia GS genome database upon the retrieval of various 5S rRNA sequences from the 5S rRNA database as queries to BLASTn search against the genome database. However, one hit (Contig ID: ACGJ01000259), which was found to possess a 36 bp sequence sharing 100% identity with the 5′ terminal region (from+1 bp to 36 bp) of 5S rRNA genes of G. lamblia WB and P15 was found when the 5S rRNA genes of the two isolates were used as queries (Figure 1). The region in contig ACGJ01000259 (309 bp long) sharing 100% identity with 5S rRNA gene (from+1 bp to 36 bp) of G. lamblia WB and P15 was found at the end of this contig (from 274 bp to 309 bp). Moreover, a 79 bp RNA fragment sharing 99% identity with the 3′ terminal region (from +39 bp to +117 bp) of G. lamblia WB 5S rRNA was once reported in G. lamblia GS [21]. In this way, the lack of a G. lamblia 5S rRNA gene in the G. lamblia GS genome database is most probably due to the numerous gaps in the database and the small number genes in this organism.

Bottom Line: Eukaryotic 5S rRNA and its associated proteins (5S rRNA system) have become very well understood.By collecting and confirming pre-existing data and identifying new data, we obtained almost complete datasets of the system of three isolates of G. lamblia, two other parasitic excavates (Trichomonas vaginalis, Trypanosoma cruzi), and one free-living one (Naegleria gruberi).Our results also imply G. lamblia might be a primitive eukaryote with secondary parasitically-degenerated features.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Genetic Resources and Evolution, Kunming Institute of Zoology, Chinese Academy of Sciences, Kunming, People's Republic of China.

ABSTRACT

Background: 5S rRNA is a highly conserved ribosomal component. Eukaryotic 5S rRNA and its associated proteins (5S rRNA system) have become very well understood. Giardia lamblia was thought by some researchers to be the most primitive extant eukaryote while others considered it a highly evolved parasite. Previous reports have indicated that some aspects of its 5S rRNA system are simpler than that of common eukaryotes. We here explore whether this is true to its entire system, and whether this simplicity is a primitive or parasitic feature.

Methodology/principal findings: By collecting and confirming pre-existing data and identifying new data, we obtained almost complete datasets of the system of three isolates of G. lamblia, two other parasitic excavates (Trichomonas vaginalis, Trypanosoma cruzi), and one free-living one (Naegleria gruberi). After comprehensively comparing each aspect of the system among these excavates and also with those of archaea and common eukaryotes, we found all the three Giardia isolates to harbor a same simplified 5S rRNA system, which is not only much simpler than that of common eukaryotes but also the simplest one among those of these excavates, and is surprisingly very similar to that of archaea; we also found among these excavates the system in parasitic species is not necessarily simpler than that in free-living species, conversely, the system of free-living species is even simpler in some respects than those of parasitic ones.

Conclusion/significance: The simplicity of Giardia 5S rRNA system should be considered a primitive rather than parasitically-degenerated feature. Therefore, Giardia 5S rRNA system might be a primitive system that is intermediate between that of archaea and the common eukaryotic model system, and it may reflect the evolutionary history of the eukaryotic 5S rRNA system from the archaeal form. Our results also imply G. lamblia might be a primitive eukaryote with secondary parasitically-degenerated features.

Show MeSH
Related in: MedlinePlus