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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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TATA-like box identified in G. lamblia WB 5S rRNA gene.The regions between −58 and −43 bp upstream the transcriptional initiation site of G. lamblia WB 5S rRNA genes all contain an AT-rich region (denoted by box), which might be the TATA-like box of G. lamblia WB 5S rRNA gene.
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pone-0036878-g003: TATA-like box identified in G. lamblia WB 5S rRNA gene.The regions between −58 and −43 bp upstream the transcriptional initiation site of G. lamblia WB 5S rRNA genes all contain an AT-rich region (denoted by box), which might be the TATA-like box of G. lamblia WB 5S rRNA gene.

Mentions: However, although no canonical TATA box was found in G. lamblia 5S rRNA genes, we have identified a 16 bp AT-rich region between −58 and −43 bp upstream of the transcriptional initiation site of these genes, whose consensus sequence is 5′-AA(T/C)A(C/T/A)(A/G) C(A/T)(G/A)(T/A)AT(G/T)(T/A)A(T/C)-3′ (Figure 3). Previous studies have indicated that the TATA boxes of G. lamblia genes are not as canonical as those of common eukaryotes. Rather, they vary with respect to their sequence, length, and exact position relative to the transcription start site [29]–[33]. Our analysis also showed a TATA box in the 5S rRNA genes of N. gruberi but not in T. cruzi (Figure 2). T. vaginalis has been reported to have TATA box in its 5S rRNA genes [23] (Table 1).


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)

TATA-like box identified in G. lamblia WB 5S rRNA gene.The regions between −58 and −43 bp upstream the transcriptional initiation site of G. lamblia WB 5S rRNA genes all contain an AT-rich region (denoted by box), which might be the TATA-like box of G. lamblia WB 5S rRNA gene.
© Copyright Policy
Related In: Results  -  Collection

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

pone-0036878-g003: TATA-like box identified in G. lamblia WB 5S rRNA gene.The regions between −58 and −43 bp upstream the transcriptional initiation site of G. lamblia WB 5S rRNA genes all contain an AT-rich region (denoted by box), which might be the TATA-like box of G. lamblia WB 5S rRNA gene.
Mentions: However, although no canonical TATA box was found in G. lamblia 5S rRNA genes, we have identified a 16 bp AT-rich region between −58 and −43 bp upstream of the transcriptional initiation site of these genes, whose consensus sequence is 5′-AA(T/C)A(C/T/A)(A/G) C(A/T)(G/A)(T/A)AT(G/T)(T/A)A(T/C)-3′ (Figure 3). Previous studies have indicated that the TATA boxes of G. lamblia genes are not as canonical as those of common eukaryotes. Rather, they vary with respect to their sequence, length, and exact position relative to the transcription start site [29]–[33]. Our analysis also showed a TATA box in the 5S rRNA genes of N. gruberi but not in T. cruzi (Figure 2). T. vaginalis has been reported to have TATA box in its 5S rRNA genes [23] (Table 1).

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