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Algal MIPs, high diversity and conserved motifs.

Anderberg HI, Danielson JÅ, Johanson U - BMC Evol. Biol. (2011)

Bottom Line: Our results suggest that at least two of the seven subfamilies found in land plants were present already in an algal ancestor.The total variation of MIPs and the number of different subfamilies in chlorophyte algae is likely to be even higher than that found in land plants.Our analyses indicate that genetic exchanges between several of the algal subfamilies have occurred.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biochemistry, Center for Molecular Protein Science, Center for Chemistry and Chemical Engineering, Lund University, PO Box 124, S-221 00 Lund, Sweden.

ABSTRACT

Background: Major intrinsic proteins (MIPs) also named aquaporins form channels facilitating the passive transport of water and other small polar molecules across membranes. MIPs are particularly abundant and diverse in terrestrial plants but little is known about their evolutionary history. In an attempt to investigate the origin of the plant MIP subfamilies, genomes of chlorophyte algae, the sister group of charophyte algae and land plants, were searched for MIP encoding genes.

Results: A total of 22 MIPs were identified in the nine analysed genomes and phylogenetic analyses classified them into seven subfamilies. Two of these, Plasma membrane Intrinsic Proteins (PIPs) and GlpF-like Intrinsic Proteins (GIPs), are also present in land plants and divergence dating support a common origin of these algal and land plant MIPs, predating the evolution of terrestrial plants. The subfamilies unique to algae were named MIPA to MIPE to facilitate the use of a common nomenclature for plant MIPs reflecting phylogenetically stable groups. All of the investigated genomes contained at least one MIP gene but only a few species encoded MIPs belonging to more than one subfamily.

Conclusions: Our results suggest that at least two of the seven subfamilies found in land plants were present already in an algal ancestor. The total variation of MIPs and the number of different subfamilies in chlorophyte algae is likely to be even higher than that found in land plants. Our analyses indicate that genetic exchanges between several of the algal subfamilies have occurred. The PIP1 and PIP2 groups and the Ca2+ gating appear to be specific to land plants whereas the pH gating is a more ancient characteristic shared by all PIPs. Further studies are needed to discern the function of the algal specific subfamilies MIPA-E and to fully understand the evolutionary relationship of algal and terrestrial plant MIPs.

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Related in: MedlinePlus

Sequence similarities between algal PIPs and MIPEs in loop E. Figure showing iceLogos of part of Loop E for MIPEs, algal PIPs and P. patens PIPs. For each of the three groups compared, the iceLogo shows the position specific over- and under representations of amino acids compared to an alignment of all MIPs included in the phylogenetic analysis. Only amino acids significantly different in the test- and reference set (P < 0.05) are shown and the size of the character reflect the difference in frequency (positive values are overrepresented whereas negative values are underrepresented in the test set). At the bottom the amino acid sequence and numbering of SoPIP2;1 is shown to ease orientation.
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Figure 3: Sequence similarities between algal PIPs and MIPEs in loop E. Figure showing iceLogos of part of Loop E for MIPEs, algal PIPs and P. patens PIPs. For each of the three groups compared, the iceLogo shows the position specific over- and under representations of amino acids compared to an alignment of all MIPs included in the phylogenetic analysis. Only amino acids significantly different in the test- and reference set (P < 0.05) are shown and the size of the character reflect the difference in frequency (positive values are overrepresented whereas negative values are underrepresented in the test set). At the bottom the amino acid sequence and numbering of SoPIP2;1 is shown to ease orientation.

Mentions: The group containing three sequences from Chlorella sp. NC64A and one from Ostreococcus RCC809 was named MIPE. They all have ar/R filters identical to that of algal PIPs and also share a conserved motif in loop E (DGCS, where the cysteine is situated at LE1 of the ar/R filter) with these (Figure 3). Furthermore, phylogenetic analyses of the C-terminal region show that these parts of the MIPEs and algal PIPs are closely related (data not shown). The MIPEs also share a motif in loop C with the mammalian classical aquaporins (LXXN). In addition, OrMIPE1;1 shares significant sequence similarity with OlMIPB1;1 and OrMIPB1;1 in loop E (Figure 4). It should be noted that CnMIPE1;3 is missing sequence information corresponding to half of H4, loop D and most of H5 due to a gap in the available genomic sequence.


Algal MIPs, high diversity and conserved motifs.

Anderberg HI, Danielson JÅ, Johanson U - BMC Evol. Biol. (2011)

Sequence similarities between algal PIPs and MIPEs in loop E. Figure showing iceLogos of part of Loop E for MIPEs, algal PIPs and P. patens PIPs. For each of the three groups compared, the iceLogo shows the position specific over- and under representations of amino acids compared to an alignment of all MIPs included in the phylogenetic analysis. Only amino acids significantly different in the test- and reference set (P < 0.05) are shown and the size of the character reflect the difference in frequency (positive values are overrepresented whereas negative values are underrepresented in the test set). At the bottom the amino acid sequence and numbering of SoPIP2;1 is shown to ease orientation.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3111385&req=5

Figure 3: Sequence similarities between algal PIPs and MIPEs in loop E. Figure showing iceLogos of part of Loop E for MIPEs, algal PIPs and P. patens PIPs. For each of the three groups compared, the iceLogo shows the position specific over- and under representations of amino acids compared to an alignment of all MIPs included in the phylogenetic analysis. Only amino acids significantly different in the test- and reference set (P < 0.05) are shown and the size of the character reflect the difference in frequency (positive values are overrepresented whereas negative values are underrepresented in the test set). At the bottom the amino acid sequence and numbering of SoPIP2;1 is shown to ease orientation.
Mentions: The group containing three sequences from Chlorella sp. NC64A and one from Ostreococcus RCC809 was named MIPE. They all have ar/R filters identical to that of algal PIPs and also share a conserved motif in loop E (DGCS, where the cysteine is situated at LE1 of the ar/R filter) with these (Figure 3). Furthermore, phylogenetic analyses of the C-terminal region show that these parts of the MIPEs and algal PIPs are closely related (data not shown). The MIPEs also share a motif in loop C with the mammalian classical aquaporins (LXXN). In addition, OrMIPE1;1 shares significant sequence similarity with OlMIPB1;1 and OrMIPB1;1 in loop E (Figure 4). It should be noted that CnMIPE1;3 is missing sequence information corresponding to half of H4, loop D and most of H5 due to a gap in the available genomic sequence.

Bottom Line: Our results suggest that at least two of the seven subfamilies found in land plants were present already in an algal ancestor.The total variation of MIPs and the number of different subfamilies in chlorophyte algae is likely to be even higher than that found in land plants.Our analyses indicate that genetic exchanges between several of the algal subfamilies have occurred.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Biochemistry, Center for Molecular Protein Science, Center for Chemistry and Chemical Engineering, Lund University, PO Box 124, S-221 00 Lund, Sweden.

ABSTRACT

Background: Major intrinsic proteins (MIPs) also named aquaporins form channels facilitating the passive transport of water and other small polar molecules across membranes. MIPs are particularly abundant and diverse in terrestrial plants but little is known about their evolutionary history. In an attempt to investigate the origin of the plant MIP subfamilies, genomes of chlorophyte algae, the sister group of charophyte algae and land plants, were searched for MIP encoding genes.

Results: A total of 22 MIPs were identified in the nine analysed genomes and phylogenetic analyses classified them into seven subfamilies. Two of these, Plasma membrane Intrinsic Proteins (PIPs) and GlpF-like Intrinsic Proteins (GIPs), are also present in land plants and divergence dating support a common origin of these algal and land plant MIPs, predating the evolution of terrestrial plants. The subfamilies unique to algae were named MIPA to MIPE to facilitate the use of a common nomenclature for plant MIPs reflecting phylogenetically stable groups. All of the investigated genomes contained at least one MIP gene but only a few species encoded MIPs belonging to more than one subfamily.

Conclusions: Our results suggest that at least two of the seven subfamilies found in land plants were present already in an algal ancestor. The total variation of MIPs and the number of different subfamilies in chlorophyte algae is likely to be even higher than that found in land plants. Our analyses indicate that genetic exchanges between several of the algal subfamilies have occurred. The PIP1 and PIP2 groups and the Ca2+ gating appear to be specific to land plants whereas the pH gating is a more ancient characteristic shared by all PIPs. Further studies are needed to discern the function of the algal specific subfamilies MIPA-E and to fully understand the evolutionary relationship of algal and terrestrial plant MIPs.

Show MeSH
Related in: MedlinePlus