Figure 2.

Osmotic water permeability of oocytes coexpressing BvPIP1;1 or BvPIP2;2 monomers with the heterodimer in a 1:1 mass ratio. P_f measurements of oocytes injected with cRNA coding for BvPIP1;1, BvPIP2;2, heterodimer, heterodimer + monomer BvPIP1;1, and heterodimer + monomer BvPIP2;2. The amount of cRNA is shown in parentheses; where (1) is equivalent to 2.5 ng of cRNA per oocyte and a (1:1) mass ratio corresponds to 2.5 ng of one cRNA plus 2.5 ng of the other cRNA. NI, noninjected oocytes used as negative controls. Oocytes expressing the heterodimer show P_f values significantly different from those of BvPIP2;2 cRNA alone. Coexpression of the heterodimer with BvPIP2;2 or BvPIP1;1 monomers in a 1:1 cRNA mass ratio show different properties in terms of membrane water permeability, stating that heterotetramers with diverse composition must be present in the plasma membrane. Data are mean (± SE) water permeability values (n = 4), and 14–18 oocytes were tested for each treatment in each independent experiment. Letters a–e denote values significantly different from each other (p < 0.05), as determined by the two-tailed Student’s t-test. To the right of each bar is indicated, in cartoon format, the plausible heterotetrameric assemblies formed by injection of each cRNA. Crossed-out tetramers are those that are not located in the plasma membrane. BvPIP1;1 monomer is represented by a solid circle, BvPIP2;2 monomer by an open circle, and the heterodimer by an open circle and a solid circle connected with a curved line.