Finding Aquaporins in Annelids: An Evolutionary Analysis and a Case Study.

Area of Science:

• Molecular Biology
• Evolutionary Biology
• Physiology

Background:

• Aquaporins (AQPs) are integral membrane proteins facilitating water and small solute transport across cell membranes.
• Their roles in osmoregulation are well-established in many organisms, but their presence and diversity in annelids remain largely unexplored.
• Annelids, a diverse phylum, play significant roles in various ecosystems, making the study of their AQPs relevant for understanding physiological adaptations.

Purpose of the Study:

• To identify and characterize aquaporin sequences within the Annelida phylum.
• To infer the evolutionary history and phylogenetic relationships of annelid aquaporins.
• To investigate the potential physiological functions of annelid AQPs, particularly in relation to osmoregulation.

Main Methods:

• Bioinformatic searches and annotation of aquaporin sequences in public annelid genomes and transcriptomes.
• Phylogenetic analyses to reconstruct evolutionary relationships among identified aquaporin sequences.
• RT-PCR validation and structural analysis of selected aquaporins from *Alitta succinea*.

Main Results:

• Identification of 401 aquaporin sequences across 27 annelid species, with 367 newly recognized.
• Phylogenetic analysis revealed four major clades (AQP1-like, AQP3-like, AQP8-like, AQP11-like), similar to vertebrates.
• Evidence of gene duplications in the AQP1-like clade within some Sedentaria families, and validation of three AQPs in the salinity-tolerant *Alitta succinea*.

Conclusions:

• The study provides a comprehensive catalog of annelid aquaporins, significantly expanding the known diversity.
• Annelid aquaporins exhibit evolutionary patterns comparable to other major animal groups, suggesting conserved functional roles.
• The findings indicate a diversification of aquaporin structures and functions within Annelida, potentially underlying adaptations to diverse environments.