Functional diversification of aquaporins: the case of the PIP subfamily

VITALI, VICTORIA ANDREA; SOTO, GABRIELA; CANESSA FORTUNA, AGUSTINA; ALLEVA, KARINA; AYUB, NICOLÁS

Congreso; SCHCF + ALACF 2020 joint meeting; 2020

The membrane intrinsic proteins (MIP) family, better known as the aquaporin (AQP) familyis a highly expanded group of channels. In eukaryotes, the best-known examples of MIPfamily expansion are land vertebrates, fishes and flowering plants. Previous phylogeneticstudies revealed that each subfamily of plant AQPs was related to a subfamily of animal AQPpredicting the presence of at least four families of AQPs in the ancestral eukaryote. We areparticularly interested in the study of plant PIP (plasma membrane intrinsic proteins)subfamily that belongs to the AQP1-like group (also called classical aquaporins). This groupincludes not only animal AQP1 but also AQP0, AQP2, AQP4, AQP5 and AQP6.PIPs constitute the largest MIP subfamily (about 10 to 30 PIP genes are encoded by species)showing high sequence identity and two main groups of paralogous (PIP1 and PIP2) even inancestral plants as Selaginella moellendorffii. For years efforts have been focused inelucidating whether this great multiplicity of isoforms implies diversity or functional overlap.Although a certain degree of redundancy is not ruled out, many pairs of duplicated genesshow different expression patterns but functional diversity at the transport level has not beenclear. The aim of our work is to analyse whether the high number of PIPs per plant presentsgenuine functional diversification. Here, we performed a comprehensive analysis of the PIPsubfamily by combining coding sequences analysis, survey of tissue expression patterns,and characterization of biological activity. We described cases of functional diversification atsolute specificity, cooperative response events and heterotetramer formation. Our resultshighlight the importance of multiple isoform conservation to describe the wide spectrum ofbiological activities. Deeping inside the PIP functional diversifications could enlarge thespectrum of biological roles of other AQP belonging to the same group and could help topredict new functions.