Abstract
Aquaporins facilitate water flux across biomembranes, and are involved in various physiological phenomena in several plant tissues. We analyzed the water-flux activity of plant aquaporins using lily (Lilium longiflorum) pollen protoplasts. Large protoplasts with a uniform diameter of approximately 95 μm were isolated from lily nearly mature pollen grains. The genes for plasma membrane aquaporins (PIPs) of Arabidopsis and carrot were put under the control of the strong pollen-specific promoter, maize Zm13 promoter, and then they were introduced into the protoplasts by electroporation. The pollen protoplasts expressed AtPIP2;1 or DcPIP2;1 increased significantly their volumes in hypotonic solution (350 mM mannitol) compared with the vector control. By contrast, the volume changes of the protoplasts expressed AtPIP1;1 or DcPIP1;1 were similar to that of the vector control. These results suggest that PIP2s show higher water-flux activity in plant cells, whereas PIP1s do not. Thus, we propose the lily pollen protoplasts as a simple and useful experimental system to analyze the function of plant aquaporins.
