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Evidence of Positive Selection of Aquaporins Genes from Pontoporia blainvillei during the Evolutionary Process of Cetaceans.

São Pedro SL, Alves JM, Barreto AS, Lima AO - PLoS ONE (2015)

Bottom Line: Marine mammals are well adapted to their hyperosmotic environment.Several morphological and physiological adaptations for water conservation and salt excretion are known to be present in cetaceans, being responsible for regulating salt balance.Many genes have been identified to be involved in osmotic regulation, including the aquaporins.

View Article: PubMed Central - PubMed

Affiliation: Laboratório de Genética Molecular, Centro de Ciências Tecnológicas da Terra e do Mar, Universidade do Vale do Itajaí, Itajaí, SC, Brazil.

ABSTRACT

Background: Marine mammals are well adapted to their hyperosmotic environment. Several morphological and physiological adaptations for water conservation and salt excretion are known to be present in cetaceans, being responsible for regulating salt balance. However, most previous studies have focused on the unique renal physiology of marine mammals, but the molecular bases of these mechanisms remain poorly explored. Many genes have been identified to be involved in osmotic regulation, including the aquaporins. Considering that aquaporin genes were potentially subject to strong selective pressure, the aim of this study was to analyze the molecular evolution of seven aquaporin genes (AQP1, AQP2, AQP3, AQP4, AQP6, AQP7, and AQP9) comparing the lineages of cetaceans and terrestrial mammals.

Results: Our results demonstrated strong positive selection in cetacean-specific lineages acting only in the gene for AQP2 (amino acids 23, 83, 107,179, 180, 181, 182), whereas no selection was observed in terrestrial mammalian lineages. We also analyzed the changes in the 3D structure of the aquaporin 2 protein. Signs of strong positive selection in AQP2 sites 179, 180, 181, and 182 were unexpectedly identified only in the baiji lineage, which was the only river dolphin examined in this study. Positive selection in aquaporins AQP1 (45), AQP4 (74), AQP7 (342, 343, 356) was detected in cetaceans and artiodactyls, suggesting that these events are not related to maintaining water and electrolyte homeostasis in seawater.

Conclusions: Our results suggest that the AQP2 gene might reflect different selective pressures in maintaining water balance in cetaceans, contributing to the passage from the terrestrial environment to the aquatic. Further studies are necessary, especially those including other freshwater dolphins, who exhibit osmoregulatory mechanisms different from those of marine cetaceans for the same essential task of maintaining serum electrolyte balance.

No MeSH data available.


Phylogenetic tree using aquaporin 2 nucleotide sequences.The tree shows relationships among mammalian groups that are consistent with those derived from more comprehensive data sets. The tree was constructed using maximum likelihood, and clade support was evaluated by bootstrap re-sampling using 100 pseudo-replicates.
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pone.0134516.g001: Phylogenetic tree using aquaporin 2 nucleotide sequences.The tree shows relationships among mammalian groups that are consistent with those derived from more comprehensive data sets. The tree was constructed using maximum likelihood, and clade support was evaluated by bootstrap re-sampling using 100 pseudo-replicates.

Mentions: All aquaporin genes identified in the P. blainvillei genome were intact and there were no premature stop codons or frameshift mutations, which indicated the presence of functional proteins. Sequences from each aquaporin gene were used to construct phylogenetic trees using likelihood and Bayesian approaches. The topologies of the ML and Bayesian consensus trees were congruent, and the tree for AQP2 is shown as a representative example (Fig 1) due to its strong positive selection in cetacean-specific lineages (see below). In all AQP genes analyzed, most higher level relationships among mammalian orders and suborders were consistent with those of larger, more comprehensive data sets [6], in all AQP genes analyzed (S1 Fig).


Evidence of Positive Selection of Aquaporins Genes from Pontoporia blainvillei during the Evolutionary Process of Cetaceans.

São Pedro SL, Alves JM, Barreto AS, Lima AO - PLoS ONE (2015)

Phylogenetic tree using aquaporin 2 nucleotide sequences.The tree shows relationships among mammalian groups that are consistent with those derived from more comprehensive data sets. The tree was constructed using maximum likelihood, and clade support was evaluated by bootstrap re-sampling using 100 pseudo-replicates.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4520692&req=5

pone.0134516.g001: Phylogenetic tree using aquaporin 2 nucleotide sequences.The tree shows relationships among mammalian groups that are consistent with those derived from more comprehensive data sets. The tree was constructed using maximum likelihood, and clade support was evaluated by bootstrap re-sampling using 100 pseudo-replicates.
Mentions: All aquaporin genes identified in the P. blainvillei genome were intact and there were no premature stop codons or frameshift mutations, which indicated the presence of functional proteins. Sequences from each aquaporin gene were used to construct phylogenetic trees using likelihood and Bayesian approaches. The topologies of the ML and Bayesian consensus trees were congruent, and the tree for AQP2 is shown as a representative example (Fig 1) due to its strong positive selection in cetacean-specific lineages (see below). In all AQP genes analyzed, most higher level relationships among mammalian orders and suborders were consistent with those of larger, more comprehensive data sets [6], in all AQP genes analyzed (S1 Fig).

Bottom Line: Marine mammals are well adapted to their hyperosmotic environment.Several morphological and physiological adaptations for water conservation and salt excretion are known to be present in cetaceans, being responsible for regulating salt balance.Many genes have been identified to be involved in osmotic regulation, including the aquaporins.

View Article: PubMed Central - PubMed

Affiliation: Laboratório de Genética Molecular, Centro de Ciências Tecnológicas da Terra e do Mar, Universidade do Vale do Itajaí, Itajaí, SC, Brazil.

ABSTRACT

Background: Marine mammals are well adapted to their hyperosmotic environment. Several morphological and physiological adaptations for water conservation and salt excretion are known to be present in cetaceans, being responsible for regulating salt balance. However, most previous studies have focused on the unique renal physiology of marine mammals, but the molecular bases of these mechanisms remain poorly explored. Many genes have been identified to be involved in osmotic regulation, including the aquaporins. Considering that aquaporin genes were potentially subject to strong selective pressure, the aim of this study was to analyze the molecular evolution of seven aquaporin genes (AQP1, AQP2, AQP3, AQP4, AQP6, AQP7, and AQP9) comparing the lineages of cetaceans and terrestrial mammals.

Results: Our results demonstrated strong positive selection in cetacean-specific lineages acting only in the gene for AQP2 (amino acids 23, 83, 107,179, 180, 181, 182), whereas no selection was observed in terrestrial mammalian lineages. We also analyzed the changes in the 3D structure of the aquaporin 2 protein. Signs of strong positive selection in AQP2 sites 179, 180, 181, and 182 were unexpectedly identified only in the baiji lineage, which was the only river dolphin examined in this study. Positive selection in aquaporins AQP1 (45), AQP4 (74), AQP7 (342, 343, 356) was detected in cetaceans and artiodactyls, suggesting that these events are not related to maintaining water and electrolyte homeostasis in seawater.

Conclusions: Our results suggest that the AQP2 gene might reflect different selective pressures in maintaining water balance in cetaceans, contributing to the passage from the terrestrial environment to the aquatic. Further studies are necessary, especially those including other freshwater dolphins, who exhibit osmoregulatory mechanisms different from those of marine cetaceans for the same essential task of maintaining serum electrolyte balance.

No MeSH data available.