Identification of Plasma Membrane Aquaporin in Guard Cells of Vicia faba and Its Role in Stomatal Movement

Water channels or aquaporins are the main pathways of water transport. Both the existence and function of aquaporins in the guard cells of Vicia faba L. were investigated both by using RD28 cDNA and RD28 antibody as probes, and by controlling stomatal movement as a parameter combined with antibody and inhibitor of aquaporins respectively. The results revealed that RD28 mRNA, encoding a plasma membrane aquaporin, expressed in the mesophyll cells and vascular tissues of V. faba , especially in guard cells. And the location of RD28_like proteins was mainly on plasma membrane of guard cells. The addition of 25 μmol/L HgCl 2, an aquaporin blocker, and antibody of RD28 as well, greatly suppressed the stomatal opening or guard_cell protoplast swelling induced by fusicoccin and light, and closing induced by abscisic acid. However, 5 mmol/L β_mercaptoethanol, a reverse reagent of aquaporin blocker, reversed the inhibitory effect of HgCl 2 pretreatment on stomatal opening (i.e., HgCl 2 was removed after HgCl 2 pretreatment for 10 min). The results suggest that the aquaporins in V. faba are associated with stomatal movement.