Abstract
Aquaporins are involved in rapid water transport across biological membranes. A. thaliana has 35 aquaporin species. In this study, we examined physiological changes in protein levels of eight species of plasma membrane aquaporins (PIP), two species of vacuolar membrane aquaporins (TIP) for understanding physiological meanings of each aquaporin isoform. Also, we analyzed their organ- and cell-growth-phase specific accumulation and responses to environmental stresses in Arabidopsis whole plants and suspension-cultured cells by using isoform-specific antibodies. In suspension-cultured cells, the protein levels of aquaporins remarkably increased after cultured for 2 weeks. The amounts of aquaporins in suspension cells were less than 10% of that in stems of whole plants. Furthermore, we determined changes in the aquaporin levels in response to osmotic (PEG) and salt (NaCl) stresses. The levels of PIP2-type and TIP1-type aquaporins increased more than twice under salt stress, while PIP1-type aquaporins kept constant levels.
