Algal MIPs, high diversity and conserved motifs

Area of Science:

• Plant Biology
• Molecular Evolution
• Biochemistry

Background:

• Major intrinsic proteins (MIPs), also known as aquaporins, facilitate transmembrane transport of water and small molecules.
• MIPs are diverse in land plants, but their evolutionary origins remain largely unknown.
• Investigating chlorophyte algae, the sister group to land plants, offers insights into early MIP evolution.

Purpose of the Study:

• To explore the evolutionary history of plant MIP subfamilies.
• To identify MIP-encoding genes in chlorophyte algae genomes.
• To understand the ancestral state of MIPs before plant terrestrialization.

Main Methods:

• Genome-wide search for MIP-encoding genes in nine chlorophyte algae species.
• Phylogenetic analyses to classify identified MIPs into subfamilies.
• Divergence dating to estimate evolutionary timelines.

Main Results:

• Identified 22 MIPs across nine algal genomes, classifying them into seven subfamilies.
• Two subfamilies, Plasma membrane Intrinsic Proteins (PIPs) and GlpF-like Intrinsic Proteins (GIPs), are shared with land plants.
• Dating suggests PIPs and GIPs originated in a common ancestor before the evolution of terrestrial plants.

Conclusions:

• At least two major land plant MIP subfamilies (PIPs, GIPs) existed in an algal ancestor.
• Chlorophyte algae may possess greater MIP diversity than land plants.
• Genetic exchanges between algal MIP subfamilies were inferred; pH gating is ancient, while Ca2+ gating is specific to land plant PIPs.