Response to salt stress in seagrasses: PIP1;1 aquaporin antibody localization in Posidonia oceanica leaves

► We analyzed histological localization of PIP1 aquaporins in leaves of seagrass Posidonia oceanica. ► We identified several errors in translation of a PIP1 EST Nucleotide Sequence found in a public database and we proposed an alternative sequence. ► We demonstrated that peptides recognized by the heterologous anti PIP1;1 antibody from Arabidopsis thaliana correspond to PIP1 aquaporins. ► Our results are evidence of an effective increase in PIP1 aquaporins expression in leaf tissues in early response to salt stress. Posidonia oceanica meadows are sensitive to disturbance often associated with highly human-impacted coasts. A recent anthropogenic impact is due to hypersaline water produced by desalination plants of seawater that severely affects growth rate, induces necrotic lesions and enhances meadow mortality. To define the early effects directly correlated to salt regime variation on leaf tissue, we focused on aquaporins, water channel proteins of intracellular and plasma membranes. PIP aquaporins localization was carried out in leaf cross sections, using an antibody raised against the evolutionarily conserved N-terminal amino acid sequence of Arabidopsis thaliana PIP1;1 (which showed 84% of identity with P. oceanica PIP1;1 aquaporin), both in leaves kept in natural seawater and in leaves subjected to hypersaline treatment. In natural seawater conditions, the antibody was localized mainly in epidermis and weakly in vascular bundles and mesophyll tissues of leaves. A widespread increase of fluorescence was observed in leaves subjected to hypersaline regime. Hence, our results showed histological evidence of PIP1;1 peptide increase following salt stress. Our data also suggest that aquaporins are involved in osmotic balance maintenance in seagrasses.