How PIP1 plant aquaporins make a difference in terms of cytosolic pH sensingand membrane osmotic permeability

AGUSTÍN YANEFF; LORENA SIGAUT; MERCEDES MARQUEZ; LÍA ISABEL PIETRASANTA; KARINA ALLEVA; GABRIELA AMODEO

Philadelphia

Congreso; 57th Annual Meeting Biophysical Society; 2013

Biophysical Society

Plant cells express in their plasma membrane (PM) a complex set of aquaporins, responsible of increasing the osmotic permeability (Pf) and thus allowing faster water adjustments. This set includes PIP aquaporins, which also sense cytosolic acidification blocking the water pathway through their pores. A subgroup known as PIP1 have proven in many different plant species to additionally request physical interaction with a PIP2 aquaporin reflecting a differential modulatory mechanism. Here we explore how a fruit specific PIP1 aquaporin from Fragaria x ananassa -FaPIP1;1- contributes to modulate the PM in terms of Pf and pH sensing. Being already characterized FaPIP2;1 properties (Alleva et al., 2010 J Exp Bot) we designed a FaPIP2;1 mutant with the initial purpose of occluding its pore by replacing a highly conserved residue (N228D). The experimental approach included i) functional studies (measuring Pf in Xenopus oocytes) and ii) localization studies (fluorescence confocal analysis employing YPF-FaPIPs). Our results show that i) FaPIP1;1 is capable of reaching the PM when coexpressed with N228D as well as FaPIP2;1, ii) the coexpression of FaPIP2;1-FaPIP1;1 resulted in higher Pf than N228D-FaPIP1;1, iii) pH sensitivity measured in terms of EC50 are the same for both coexpressions. Our results allows us to hypothesized that the Pf showed by the coexpression of FaPIP1;1-N228D could represent FaPIP1;1 water transport capacity, being N228D inactive as a water channel. The contribution of FaPIP1;1 is relevant in terms of increasing faster water adjustments in the PM and allowing blocking the pores at a more physiological pH.