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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

Alternative interaction network of MIPBs and MIPEs. MIPBs and MIPEs have unusual substitutions in helix 3 and loop B suggesting an alternative network of interactions in the packing core next to the pore at the cytoplasmic side. SoPIP2;1 is shown in green and a model of OlMIPB1;1 is superimposed in brown. The side chains at the substituted positions are drawn as sticks and their potential interactions are indicated by dashed lines with distances in Å.
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Figure 5: Alternative interaction network of MIPBs and MIPEs. MIPBs and MIPEs have unusual substitutions in helix 3 and loop B suggesting an alternative network of interactions in the packing core next to the pore at the cytoplasmic side. SoPIP2;1 is shown in green and a model of OlMIPB1;1 is superimposed in brown. The side chains at the substituted positions are drawn as sticks and their potential interactions are indicated by dashed lines with distances in Å.

Mentions: In addition MIPBs and some MIPEs share unusual substitutions at positions that are part of a structurally conserved network of hydrogen bonds indirectly anchoring the short cytosolic C-terminal helix in AQP5 and the D-loop in the closed conformation of SoPIP2;1 [34]. At two positions in this network, at the beginning of H3, all MIPBs and MIPEs have unusual substitutions where glutamine and asparagine replace arginine and tyrosine, respectively. Furthermore, an among most MIPs conserved histidine in the B loop is replaced by glutamine in MIPBs, OrMIPE1;1 and CnMIPE1;1. These substitutions suggest that a different network of interactions can be expected in MIPBs and MIPEs (Figure 5), possibly causing changes in the properties of the cytosolic portion of the pore by affecting the conformation of the B-loop preceding the first NPA box.


Algal MIPs, high diversity and conserved motifs.

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

Alternative interaction network of MIPBs and MIPEs. MIPBs and MIPEs have unusual substitutions in helix 3 and loop B suggesting an alternative network of interactions in the packing core next to the pore at the cytoplasmic side. SoPIP2;1 is shown in green and a model of OlMIPB1;1 is superimposed in brown. The side chains at the substituted positions are drawn as sticks and their potential interactions are indicated by dashed lines with distances in Å.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 5: Alternative interaction network of MIPBs and MIPEs. MIPBs and MIPEs have unusual substitutions in helix 3 and loop B suggesting an alternative network of interactions in the packing core next to the pore at the cytoplasmic side. SoPIP2;1 is shown in green and a model of OlMIPB1;1 is superimposed in brown. The side chains at the substituted positions are drawn as sticks and their potential interactions are indicated by dashed lines with distances in Å.
Mentions: In addition MIPBs and some MIPEs share unusual substitutions at positions that are part of a structurally conserved network of hydrogen bonds indirectly anchoring the short cytosolic C-terminal helix in AQP5 and the D-loop in the closed conformation of SoPIP2;1 [34]. At two positions in this network, at the beginning of H3, all MIPBs and MIPEs have unusual substitutions where glutamine and asparagine replace arginine and tyrosine, respectively. Furthermore, an among most MIPs conserved histidine in the B loop is replaced by glutamine in MIPBs, OrMIPE1;1 and CnMIPE1;1. These substitutions suggest that a different network of interactions can be expected in MIPBs and MIPEs (Figure 5), possibly causing changes in the properties of the cytosolic portion of the pore by affecting the conformation of the B-loop preceding the first NPA box.

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