The multifunctional plant PIP aquaporin subfamily: a picture of fucnitonal diversity

TESAN, FIORELLA C; VITALI, VICTORIA ANDREA; SOTO, GABRIELA; BUSSOLINI LIZUNDIA, ROCIO; ALLEVA, KARINA

Congreso; XXXIII Argentinian meeting of plant physiology; 2021

An increasingly large number of genes have been identified as multi-functional, being those functions dependent upon biological context. In particular, variations in transported solute specificity impact channels family functions. The PIP (plasma membrane intrinsic proteins) subfamily is the largest of the seven MIP (Major intrinsic proteins, i.e. aquaporins) subfamilies found in plants. Though PIP were originally proposed as canonical water channels, there are also reports of permeability to different small solutes, such as hydrogen peroxide, carbon dioxide, and sodium. For years, efforts have been focused on elucidating whether this great multiplicity of PIP isoforms implies functional diversity or a functional overlap. Now it is becoming clearer that different isoforms do not exhibit the same functional properties in terms of solute permeability even with primary sequence identity higher than 80%. Here, we performed an extensive analysis of the PIP subfamily by implementing a systematic analysis of signature sequences and residues of all PIP isoforms from the PF00230 Pfam database entry (2034 sequences). A sequence similarity network (SSN) for the PIP subfamily was built using the EFI-EST online tool and visualized in Cytoscape 3.8.2. Based on neighborhood connectivity, we characterized the topology of the PIP subfamily within SSN clusters. To go in depth in their functional diversification, we complemented the SSN with the transport specificity reported for PIP in the literature. This approach allows us to get insights regarding their structure-functions relationships, and generate testable hypotheses about the uncharacterized isoforms in the PIP subfamily.