Increase in aquaporin activity is involved in leaf succulence of the euhalophyte Suaeda salsa, under salinity

Plasma membrane aquaporins (AQPs) determine, likely among other functions, the water relations of plant cells. We were interested in determining whether AQPs could be regulated in the process of changing leaf succulence, especially during changes in seedlings of a euhalophyte Suaeda salsa (L.), under salinity. Seedlings were treated with 100mM NaCl for 10 days. The effect of NaCl on hydraulic conductance (L-o) in roots, succulence degree. osmotic potential, Na+ and Cl- content, water permeability of protoplasts, expression of SsPIP, and amount of SsPIP AQP in leaves of S. salsa were determined. The results showed a correlation between leaf succulence and hydraulic conductance in the roots of S. salsa, under salinity. Also, the water permeability of the protoplasts of NaCl-treated leaves was significantly higher than that of controls, and the abundance of transcripts for a plasma-membrane AQP homologous to AtPIP2;7 increased in the presence of NaCl. Immunoblot analyses of PIP AQPs located in plasma membrane-enriched fractions of S. salsa seedlings showed a significant increase under salinity. In conclusion, the increase in salinity-induced AQP activity is by way of an increase in both the transcripts and protein amount, which correlate with the increase in leaf succulence of S. salsa under salinity. (C) 2008 Published by Elsevier Ireland Ltd.