WATER TRANSPORT IN PLANTS: FROM MOLECULES TO WHOLE PLANT
Aquaporins are membrane proteins which provide a very efficient membrane transport system for water and
low molecular weight compounds in living cells. We identified 23 barley aquaporin genes. Among
tonoplast-type aqauporins (TIPs), TIP3;1 seems to be essential for seed maturation. Expressions of several
plasma-membrane type aquaporins (PIPs) were down-regulated after strong salt (200 mM NaCl) or osmotic
(360 mM mannitol) stresses, probably to prevent dehydration during salt/osmotic stresses. Inactivation of PIPs
by dephosphorylation and internalization is also functional mechanism to prevent dehydration. Another
regulation mechanism of PIP activity, heteromerization between PIP1 and PIP2 subgroups, was also investigated.
Our research indicates that aquaporins are also involved in low-temperature tolerance. Molecular
engineering/enhancement of aquaporins’ functions may improve water relations, tolerance to some stresses,
nutrition uptake, and finally increase of crop yield in future.