PIP1 Aquaporins Are Concentrated in Plasmalemmasomes of Arabidopsis thaliana Mesophyll

The PIP1 subfamily of water channel proteins (aquaporins) constitute about 1% of the plasma membrane (PM) proteins from Arabidopsis thaliana leaves. Immunogold electron microscopy has confirmed their localization at the PM of mesophyll cells. Very high labeling density at PM invaginations known as plasmalemmasomes was observed. Therefore, we suggest that these subcellular structures are involved in water transport between the apoplast and the vacuole.